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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
EU NON-NATIVE ORGANISM RISK ASSESSMENT SCHEME
Name of genus: Ameiurus Rafinesque, 1820 – bullheads
Ameiurus brunneus Jordan, 1877 – snail bullhead
Ameiurus catus (Linnaeus, 1758) – white catfish, white bullhead
Ameiurus melas (Rafinesque, 1820) – black bullhead,
Ameiurus natalis (Lesueur, 1819) – yellow bullhead,
Ameiurus nebulosus (Lesueur, 1819) – brown bullhead,
Ameiurus platycephalus (Girard, 1859) – flat bullhead
Ameiurus serracanthus (Yerger and Relyea, 1968) – spotted bullhead
Retrieved [November, 11, 2016] from the Integrated Taxonomic Information System on-line database, http://www.itis.gov.
Author: Deputy Direction of Nature (Spanish Ministry of Agriculture and Fisheries, Food and Environment)
Risk Assessment Area: Europe
Draft: 20 of December
Final version: 31/01/2016
Peer reviewed by: Emili García-Berthou, Professor of Ecology. University of Girona. Institut of Aquatic Ecology. 17003 Girona, Catalonia,
Spain. Tel.: +34 972 41 8369. http://www.udg.edu/greco; Personal web page: http://www.invasiber.org/GarciaBerthou/;
https://twitter.com/garciaberthou
Peer reviewed by: Felipe Morcillo Alonso. Associate Professor. Ecology Department. Complutense of Madrid University. email:
[email protected]; www.felipemorcillo.com
Date of finalisation: 22/01/2017
Date of finalisation: 23/01/2016
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
This Risk Assessment refers to genus Ameiurus and includes information about the most representative species, which have been introduced in Europe and
established populations in at least one country. The characteristics of these species are representative for the genus Ameiurus.
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EU CHAPPEAU
QUESTION
RESPONSE
1. In how many EU member states has these species been recorded?
List them.
Ameiurus melas (Black bullhead):
Austria, Germany (Wiesner et al, 2010), Bulgaria (Uzunova y Zlatanova, 2007),
Poland (Nowak, 2010), Belgium, France, Italy, The Netherlands, UK (Holčík, 1991;
Rutkayová et al., 2013), Portugal (Ribeiro et al, 2006), Spain (Elvira, 1984), Croatia
(Jelić et al, 2010), Slovenia (Piria et al, 2016), Czech Republic (Hartvich and Lusk,
2006), Romania (Wilhelm 1998; Gaviloaie and Falka 2006), Hungary (Bódis et al,
2012), Slovakia (Koščo et al., 2004; Rutkayová et al., 2013), Denmark, Finland
(Secretariat of NOBANIS, 2012), Ireland (Minchin, 2007; CABI, 2015a) and
possible Greece (Barbieri, 2015).
Ameiurus nebulosus (Brown bullhead):
Belgium, Bulgaria, Netherlands, UK (Olenin et al., 2008); Austria, Poland, Portugal,
Spain, Italy, France, Germany, Czech Republic (Froese and Pauly, 2016); Croatia,
Slovenia (Piria et al, 2016); Estonia, Ireland, Slovakia, Sweden (Secretariat of
NOBANIS, 2012); Bulgaria, Finland, Romania (Global Invasive Species, 2016);
Luxembourg (Ries et al, 2014); Greece (Barbieri, 2015); Denmark, Hungary,
Ireland, UK (CABI, 2015b; Rutkayová,et al.,2013)
Ameiurus natalis (Yellow bullhead):
There are a number of reports of its introduction into Italy (Welcomme, 1988;
Holcík, 1991; Froese and Pauly, 2016). However, there is no reliable evidence for
this. (CABI, 2009).
Ameiurus catus (White catfish)
UK (Britton and Davies, 2006; Zieba, 2010), Poland (Nowak et al. 2008, 2010)
There is no information about the introduction of any of the other three species of
Ameiurus in Europe.
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2. In how many EU member states has this species currently
established populations? List them.
The unclear taxonomic status of both A. melas and A. nebulosus resulted in more
doubts about the occurrence of these species in some countries (Rutkayová et al.,
2013).
Related to Central and North Europe countries and according to Secretariat of
NOBANIS (2012), Ameiurus melas and Ameirus nebulosos are classified in the
Category 2 “Species with no detailed distribution map available. Species are
established in the NOBANIS region either recently or has been for a longer period of
time but are still expanding their introduced range. Risk profiles of category 2
species will be useful for countries to create their alarm list“.
Ameiurus melas
The black bullhead (Ameiurus melas) is known to have been introduced to most of
the European countries as pointed-out in the first question, but established selfsustaining populations have been confirmed for: Belgium, The Netherlands
(Verreycken et al. 2010), Austria (Wiesner et al. 2010), Germany (Wolter and Röhr,
2010), Czech Republic (Musil et al., 2008), UK (Wheeler, 1979; Copp et al, 2016),
France (Copp, 1989; Cucherousset et al., 2006 ), Hungary (Bódis et al. 2012), Italy
(Pedicillo et al. 2009), Poland (Nowak et al. 2010a, Nowak et al. , 2010b;
Grabowska, 2010), Portugal (Gante and Santos 2002; Ribeiro et al. 2006), Romania
(Wilhelm, 1998; Gaviloaie and Falka), Slovakia (Koščo et al., 2010), Croatia (Ćaleta
et al., 2011), Slovenia (Piria et al, 2016), Spain (Miranda et al., 2010, De Miguel et
al., 2014); Finland (Secretariat of NOBANIS, 2012), Ireland (Welcomme, 1988).A
total of 18 countries of the 28 Member states.
Ameiurus nebulosus:
Kottelat and Freyhof (2007) indicated that it is established in Germany, Italy and
Finland. Although (CABI, 2015b) mention that it is established in many European
countries, A. nebulosus has often been mistaken for A. melas (See Rutkayová et al.,
2013)
The distribution of A. melas has been described quite well. Its occurrence was
confirmed in a large part of Europe, e.g. In Germany, the Czech Republic, Poland,
Slovakia, Hungary, Romania. Concerning the populations of A. nebulosus, the
situation is different. They have been recorded rather incoherently and mainly in
central and eastern parts of Europe (up to Kuban and Volga drainages). Taking into
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account these facts, it can be assumed, that the real distribution of both species is
possibly wider (Kottelat and Freyhof, 2007).
Taking into account the paragraphs above, we found references of establishment in
the following countries. According to Savini et al. (2010) he fish has established
feral populations in 19 European countries according to. We found references of this
establishment for the next countries: Belgium (Verreycken et al, 2010), Bulgaria
(Uzunova and Zlatanova, 2007), Finland (Food Agriculture Organization of the
United Nations, 1997), Germany (Scott and Crossman, 1973), Hungary (Food
Agriculture Organization of the United Nations, 1997), Italy (Amori et al., 1993),
Poland (Food Agriculture Organization of the United Nations, 1997) ; Austria,
Czech Republic, Denmark, France, Ireland, Netherlands, Romania, Slovakia
(Global Invasive Species Database, 2016), Spain, Portugal (Kottelat and Freyhof,
2007), Greece (Barbieri, 2015). Elvira (2001) also points out Slovenia.
In the UK, there are some species that have been mentioned in one or more literature
sources, but scrutiny of the evidence has either refuted, or raised sufficient doubt,
that they were ever introduced in the UK (i.e. brown bullhead Ameiurus nebulosus
(Britton et a.l, 2010).
Ameiurus natalis was reported as established in Italy (Elvira, 2001). This fact was
confirmed only ten years after Gandolfi et al. (1991) had reported there were
occurrences of the Yellow catfish in Italy. However, it does not seem to be
established in Europe.
Ameiurus catus:
There is no information available about the establishment of this species in UK and
Poland (where it certainly has been introduced) or in other countries in Europe.
3. In how many EU member states has this species shown signs of
invasiveness? List them.
Ameiurus melas:
Most of the European countries recognize the evidence of invasiveness in their
waters, for instance: France, Poland, Spain, Portugal, Germany, Hungary, Slovakia,
Czech Republic, Italy, Romania, Croatia and Slovenia.
Giving the characteristics of this species as described in Invasive Species
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Compendium of the Centre for Agriculture and Biosciences International (CABI) –
(abundant in its native range; capable of securing and ingesting a wide range of
food; gregarious; broad native range; high reproductive potential; longevity (4-5
years); highly adaptable to different environments; invasive in and outside its native
range; a habitat generalist; tolerant of shade and poor quality waters) , this species
can be considered invasive for all the countries where it has established populations.
As mentioned before, those countries are:
Belgium, The Netherlands (Verreycken et al. 2010), Austria (Wiesner et al. 2010),
Germany (Wolter and Röhr 2010), Czech Republic (Musil et al. 2008), UK
(Wheeler, 1979; Copp et al, 2016), France (Copp, 1989; Cucherousset et al., 2006 ),
Hungary (Bódis et al. 2012), Italy (Pedicillo et al. 2009), Poland (Nowak et al.
2010a, Nowak et al. , 2010b; Grabowska, 2010), Portugal (Gante and Santos 2002;
Ribeiro et al. 2006), Romania (Wilhelm, 1998; Gaviloaie and Falka), Slovakia
(Koščo et al., 2010), Croatia (Ćaleta et al., 2011), Slovenia (Piria et al, 2016), Spain
(Miranda et al., 2010, De Miguel et al., 2014); Finland (Secretariat of NOBANIS,
2012), and Ireland (Welcomme, 1988).
Novomeská et al. (2013), for example, studied A. melas from four European
countries and consider it a species with “high invasive potential” due to
characteristics such as “high reproductive potential, parental care, omnivory,
aggressive behaviour and considerable tolerance to water pollution, turbidity, low
oxygen concentration, elevated temperatures and a range of pH values”.
The black bullhead has been ranked in several European countries/regions as
representing a high risk of being invasive, including Belgium, Iberia and the UK but
medium risk in Finland. This invasiveness is demonstrated in some countries, e.g.
France where it is among the few freshwater fish listed with a legal status of
‘invasive’. Whereas in the UK, only one of a few reported populations has been
confirmed though the species has nonetheless been the subject of regulation since
the 1980 (Copp et al., 2016). Related to UK, Ruiz-Navarro et al. (2015) conclude
that there was little evidence to suggest that the inability of A. melas to be invasive
in the UK was related to insufficient summer temperatures for their reproduction,
with their integration into the food web at a relatively high trophic level suggesting
that they also have access to ample food resources to facilitate their persistence.
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Thus, the continuation of their lag phase in the UK appears more related to their lack
of dispersal opportunities from this single population in the wild than through
ecological constraints. Correspondingly, should individuals from this population
disperse in the future, then invasive populations might subsequently develop.
Ameiurus nebulosus:
According to NOBANIS, this species is recognized as invasive (including here that
countries where it is considered potentially invasive) in at least 6 countries.
Source: https://www.nobanis.org/species-info/?taxaId=8496
Conversely, according to Savini et al. (2010), the fish has established feral
populations in 19 European countries.
Kottelat and Freyhof (2007) indicated that it is established in Germany, Italy and
Finland. Although CABI (2009) mentions that it is established in many European
countries, A. nebulosus has often been mistaken for A. melas (See Rutkayová et al.,
2012). The unclear taxonomic status of both A. melas and A. nebulosus resulted in
more doubts about the occurrence of these species in some countries (Rutkayová et
al., 2013).
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Having all these possible mistakes in mind, we found references of establishment for
the next 18 countries:
Belgium (Verreycken et al., 2010), Bulgaria (Uzunova and Zlatanova, 2007),
Finland (Food Agriculture Organization of the United Nations, 1997), Germany
(Scott and Crossman, 1973), Hungary (Food Agriculture Organization of the United
Nations, 1997), Italy (Amori et al., 1993), Poland (Food Agriculture Organization
of the United Nations, 1997), Austria, Czech Republic, Denmark, France, Ireland,
Netherlands, Romania, Slovakia, (GLOBAL INVASIVE SPECIES DATABASE,
2016); Spain, Portugal (Kottelat and Freyhof, 2007); Greece (Barbieri, 2015).
Giving the characteristics of this species (abundant in its native range; capable of
securing and ingesting a wide range of food; fast growing; broad native range; high
genetic variability; high reproductive potential; highly adaptable to different
environments; highly mobile locally; a habitat generalist; pioneering in disturbed
areas; invasive outside its native range as described in http://www.cabi.org/isc/) it
can be considered invasive for all the countries where it has established populations.
4. In which EU Biogeographic areas could this species establish?
There is no information about A. catus and A. natalis as invasive species in Europe,
so it is possible that we are in time to prevent the invasion of the rest of the
Ameiurus species.
Ameiurus melas is established in Continental, Atlantic, Mediterranean and Boreal
zones. It is casual in the Arctic zone. Once introduced, the dispersal rate of the
species in the Central and North European countries was medium all these areas was
medium. (Secretariat of NOBANIS, 2012).
Ameiurus nebulosus
is established in Alpine, Continental, Atlantic and Boreal zones. Once introduced,
the dispersal rate the Central and North European countries was medium of the
species in all these areas was medium. (Secretariat of NOBANIS, 2012).
Ameiurus natalis was reported as established populations in Italy (Elvira, 2001).
This fact was confirmed only ten years after Gandolfi et al. (1991) had reported
there were occurrences of the Yellow catfish in Italy. However, it does not seem to
be currently established in Europe.
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Ameiurus catus is present in Atlantic and continental regions.
5. In how many EU Member States could this species establish in the
future [given current climate] (including those where it is already
established)? List them.
It is to expect that the rest of the species of Ameiurus have the capacity to establish
in the same biogeographic areas.
Ameiurus melas:
The species is already established in Bulgaria, Finland, Germany, Hungary, Italy,
Poland, UK, Austria, Czech Republic, Denmark, France, Ireland, Netherlands,
Romania, Slovakia, Spain; Portugal, and possible in Greece (where A. nebulosus
was confirmed as established; Barbieri, 2015 recognizes that “identification errors
between A. nebulosus and the closely related A. melas are possible”)
This species could establish in Luxembourg as a result of a natural spread process
(Copp et al, 2016). In Sweden could also establish as a result of natural spread as it
is already established in Finland. In Letonia, Estonia and Lithuania there are fewer
possibilities to establish because it is not recorded in those countries and because of
the boreal climate, but once introduced and due to climate warming, this is not
impossible. There is no information about the existence of this species in Malta and
Cyprus and it is not confirmed as established in Greece but probably the species of
the genus Ameiurus would adapt to the climatic condition in these countries as the
clime is alike to the zones where the species is established already.
The study developed by the Secretariat of NOBANIS in 2012 found that A. melas
did not establish population in Latvia, Lithuania or Estonia (countries with boreal
climate) but A. nebulosus (with very similar requirements) was recorded in Estonia.
Ameiurus nebulosus:
The species is established in at least 18 countries: Finland (Food Agriculture
Organization of the United Nations, 1997), Bulgaria, Austria, Ireland, Poland,
Portugal, Spain, Italy, France, Germany, Czech Republic (Froese et al., 2016);
Ireland, Finland (Secretariat of NOBANIS, 2012); Hungary, Romania (Global
Invasive Species Database, 2016); Greece (Barbieri, 2015).
In conclusion A. nebulosus could establish anywhere in Europe, where it seems not
to be established yet: Malta, Cyprus, Croatia, Slovenia, Luxembourg, Latvia,
Lithuania, Estonia, Sweden (similar climate to other countries where it is already
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established or because it is closed and easy to spread). A recently established
population was located in 2012 in Lake Kerkini, probably introduced from Bulgaria
(Barbieri, 2015).
Ameiurus natalis was reported as with established populations in Italy (Elvira,
2001). This fact was confirmed only ten years after Gandolfi et al. (1991) had
reported there were occurrences of the Yellow catfish in Italy. However, it does not
seem to be currently established in Europe; there is no information about his
presence in other EU countries. This species could establish anywhere, at least in
Mediterranean zone.
Ameiurus catus seems not to be established yet, but it´s presence was recently
confirmed in Poland (Nowak, 2008) and UK (Britton, 2006).
It seems that not only A. melas and A. nebulosus are able to establish self-sustaining
populations in Europe. Further establishment in Great Britain of A. nebulosus may
be hindered by the temperate climate. This would inhibit reproduction, as it requires
temperatures >21° C (Kazyak and Raesby, 2003).
The North American catfish Ameiurus catus was recorded as introduced to Europe
for the first time in Great Britain. An albino variety of 620 mm fork length and 4550
g was believed to have been an ornamental fish that was introduced subsequently
into the wild (Britton and Davies, 2016).
We consider that the characteristics of the genus Ameiurus makes all the species
desirable candidates to establish in Europe, once introduced.
In the aquatic ecosystems the influence of zonal factors such as variations in
temperature and precipitation is not very relevant, so that it is possible to speak of a
remarkable homogeneity of the aquatic environment throughout the world. This fact
supports the idea that Ameiurus spp. could establish anywhere is introduced.
6. In how many EU member states could this species become invasive
in the future [given current climate] (where it is not already
established)?
Ameiurus melas:
Using an invasiveness screening tool for freshwater fishes, FISK (Copp et al. 2009),
the black bullhead has been ranked in several European countries/regions as
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representing a high risk of being invasive, including Belgium, Spain, Portugal and
the UK (Verbrugge et al., 2012; Almeida Real et al., 2013; Simonović et al., 2013;
Tarkan et al., 2014; Piria et al. 2016), but medium risk in Finland (Puntila et
al. 2013).
The species could become invasive in many of Europe’s rivers, if established. The
confidence of this prediction is higher in freshwater habitats, from small farm ponds
to large lakes, creeks and rivers. They prefer soft bottoms, avoiding free flowing
waters where water moves rapidly. They can tolerate poorly oxygenated, polluted,
turbid, and high temperature waters.
According to DAISIE, A. melas is declared as invasive in Belgium, Czech Republic,
UK, Germany and Italy, but established populations in 19 European countries.
Summarizing it may establish in the hole 28 EU Member states.
Ameiurus nebulosus:
According to NOBANIS, Ameiurus nebulosus is considered invasive in 6 countries
included in NOBANIS Network (See question 3, above) but see above about
taxonomic uncertainty.
In Scandinavian countries (Finland, Sweden) it seems that this species demonstrated
a lower risk of becoming invasive than in countries of intermediate or lower
latitudes. The same for the countries with boreal climate (as Latvia and Lithuania),
but nevertheless the species already exists in Estonia.
The rest of the countries where A. nebulosus has not established populations for
now, the risk to become invasive depends of the future introductions or if it spreads
naturally (Luxembourg, Croatia, Cyprus, Malta are countries with similar conditions
to the countries where it already established populations).
A. natalis has all the characteristics of a successful invader (abundant in its native
range; capable of securing and ingesting a wide range of food; broad native range;
highly adaptable to different environments; highly mobile locally; habitat
generalist), so it could establish in any country where A. melas and A. natalis (very
similar species) are established.
About A. catus there is less information because for now it has not established
populations in Europe but it has the same characteristics of a successful invader of
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the other species of Ameiurus. So we can assume that it could become invasive in
any country where introduced.
In conclusion for all Ameiurus species there is a major risk of becoming invasive in
any European country once introduced.
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SECTION A – Organism Information and Screening
Stage 1. Organism Information
RESPONSE
[chose one entry, delete all
others]
COMMENT
1. Identify the organism. Is it clearly a single
taxonomic entity and can it be adequately
distinguished from other entities of the same
rank?
Yes.
This Risk Assessment refers to
genus Ameiurus and includes
information about the most
representative species, species
that have been introduced in
Europe
and
established
populations in at least one
country.
The genus Ameiurus (Rafinesque, 1820) is part of Siluriformes Order
(silures, catfishes) and Ictaluridae Family (Gill, 1861) – bullhead
catfishes, North American freshwater catfishes.
From the Integrated Taxonomic Information System
(http://www.itis.gov) Ameiurus spp. comprises the following species:
 Ameiurus brunneus Jordan, 1877 – snail bullhead
 Ameiurus catus (Linnaeus, 1758) – white catfish, white bullhead
 Ameiurus melas (Rafinesque, 1820) – black bullhead
 Ameiurus natalis (Lesueur, 1819) – yellow bullhead
 Ameiurus nebulosus (Lesueur, 1819) – brown bullhead
 Ameiurus platycephalus (Girard, 1859) – flat bullhead
 Ameiurus serracanthus (Yerger and Relyea, 1968) – spotted
bullhead
Ictaluridae comprises eight genera (one extinct) and 67 species—51
living (12 with fossil records) and 16 extinct (Arce-H. et al., 2016).
Monophyly of living Ictaluridae is well supported by molecular data
analysed using parsimony and model-based methods. These analyses
found further support for the monophyly of the genus Ameiurus. This
genus is represented by16 species of which nine are fossils. Within
Ameiurus, the basal split is between A. pectinatus, the oldest fossil
species, and all other species. At the next higher node is a split between a
clade with A. reticulatus plus A. natalis and a second clade with all the
other species included in the analysis (Arce-H. et al., 2016).
All bullhead species have an adipose fin between their dorsal and tail
fins. This small fleshy fin lacks any hard, internal structures such as bone
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or cartilage. Bullheads have a rounded tail which will help distinguishing
them from small channel catfish that have a forked tail. Bullheads have
no scales, their bodies are covered with taste buds, and will be very
slippery to handle. Finally, bullheads have a single, sharp spine in the
dorsal and pectoral fins. Like other members of the Catfish Family,
bullheads also have barbels (‘whiskers’) under their chin that help them
located food (Minnesota Department of Natural Resources, 2016).
Some
species
could
be
misidentified
as
Ictalurus (Rafinesque, 1820 – channel catfishes, forktail catfishes), a
genus of the same family: Ictaluridae, (Gill, 1861). For instance I.
punctatus (channel catfish) has been known to mate with brown bullhead
(Ameiurus nebulosus), yellow bullhead (Ameiurus natalis), and black
bullhead (Ameiurus melas), resulting in a variety of hybrid catfish
(Florida
Museum
of
Natural
History.
Online:
https://www.flmnh.ufl.edu/fish/discover/species-profiles/ictaluruspunctatus/)
With regard to the Ameiurus genus, the problem is with brown and black
bullheads, given difficulties to identify Ameiurus species (Lenhardt et al,
2011).
One of the main distinguishing features separating Ameiurus melas and
Ameiurus nebulosus is that the black bullhead is with rough or irregular
small barbs on the trailing edge of the pectoral spines weak; whereas for
the brown bullhead, the pectoral spike edge is with regular saw-like
barbs. Other distinguishing features include the number of anal ray fins;
the black bullhead has 15-21 anal ray fins, the brown bullhead 21-24.
The colour pattern also varies with black bullhead being mainly solid
and dark, with a white or yellow belly; faint pale yellow vertical bar at
base of tail while the brown bullhead is usually mottled, but may be
solid, generally yellow brown or grayish, belly usually cream or tan; no
bar at base of tail (CABI, 2015a).
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Ameiurus natalis is similar to the black bullhead, A. melas and brown
bullhead, A. nebulosus. A. natalis can be distinguished from these
species by its cream-white chin barbels. A. melas has dusky or black chin
barbels, a rounded anal fin and fewer anal rays (19-23) and rakers on the
first gill arch (15-21). A. nebulosus, is usually mottled on the side of the
body, has dusky or black chin barbels and fewer anal rays (19-23)
(CABI, 2009).
Brown bullheads (Ameiurus nebulosus) are known to hybridize naturally
with closely related black (Ameiurus melas) and yellow bullhead
(Ameiurus natalis) species (Hunnicutt et al., 2005).
The species in the same genus are sometimes very difficult to distinguish
one from another (especially A. melas and A. nebulosus).
Ameiurus melas (Rafinesque,1820)
EN: Black bullhead, DE: Schwarzer Katzenwels, FR: Poisson-chat,
IT:Pesce gatto, ES:Pez gato negro.
Ameiurus nebulosus (Lesueur, 1819)
EN: Brown bullhead; DE: Brauner Katzenwels; FR: Barbotte brune; ES:
Pez gato; Barbú torito.
Ameiurus natalis (Lesueur, 1819)
EN: Yellow bullhead; DE: Gelber Katzenwels; FR: Barbotte jaune; IT:
Pesce gatto; ES: Cabeza de toro; Pez gato; Bagre torito amarillo.
Ameiurus catus (Linnaeus, 1758) – EN: White catfish, White bullhead;
DE: Weiße Katzenwels; FR: Poisson-chat blanc; IT: Pesce gatto; ES:
Barbú cabezón.
2. If not a single taxonomic entity, can it be
redefined? (if necessary use the response box
to re-define the organism and carry on)
NA
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3. Does a relevant earlier risk assessment
exist? (give details of any previous risk
assessment)
No
Using an invasiveness screening tool for freshwater fishes the black
bullhead has been ranked in several European countries/regions as
representing a high risk of being invasive, including Belgium, Iberia, and
the UK, but medium risk in Finland. This invasiveness is demonstrated
in some countries, e.g. France where it is among the few freshwater fish
listed with a legal status of ‘invasive’. Whereas in the UK, only one of a
few reported populations has been confirmed, though the species has
nonetheless been the subject of regulation since the 1980s. Data on that
lone population in England is limited to morphology and an initial study
of gonad development and dietary breadth (Ruiz-Navarro et al. 2015).
A Risk Assessment for Ameiurus melas has been conducted in Balkans
Region and the result was that the species has medium-high risk to
become invasive (Simonović et al., 2013), Applying FISK v2 to the
Iberian Peninsula, Almeida et al. (2013) classified A. melas as with “very
high” invasive risk (maximum categorical score)
Ameiurus melas is categorized as “high risk” and Ameiurus nebulosus as
“moderately high risk” of being invasive applying the Fish Invasiveness
Screening Kit (FISK) in the drainage basin of Lake Balaton (Hungary).
(Ferincz et al., 2016).
Verbrugge et al. (2012) carried out a comparison of available risk
classifications for fish in various countries, where risk assessment
protocols in force have been applied in their national context.
BE1
DE2
AT2 FISK/FI- UK4 IE5
CH6
ISK
Ameiurus Watch Black Grey High
n.r. Medium n.a.
nebulosus list
list
list
risk4
risk
(Lesueur,
1819)
BE: Belgium, DE: Germany, AT: Austria, UK: United Kingdom, IE:
Ireland, CH: Switzerland; n.a.: not applicable because protocol is limited
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to only one taxonomic group; n.r.: not reviewed. 1 Harmonia Database
(2010); 2 Nehring et al. (2010) for fish species; 4 Non-native Species
Secretariat (2010); 5 Invasive Species Ireland (2007); 6 Swiss
Commission for Wild Plant Conservation (2008); (Verbrugge et al.,
2012)
Verbrugge et al. (2012) indicates that risk classifications from one region
cannot be applied to other regions without inserting a caveat.
Ameiurus nebulosus is categorized as “high risk” of being invasive in
Greece applying FISK (Perdikaris et al., 2016).
Ameiurus melas is categorized as “high risk” and Ameiurus nebulosus as
“high risk” of being invasive applying FISK in Croatia and Slovenia.
(Piria et al., 2016).
4. If there is an earlier risk assessment is it
still entirely valid, or only partly valid?
No
In the study in Balkan region they only consider single countries.
This present Risk Assessment pretends to actualize the information for
all the EU countries about A. melas, and encompass the genus Ameiurus.
5. Where is the organism native?
North America
Ameiurus melas:
Native to the Great Lakes, Hudson Bay, and Mississippi River basins in
most of the eastern and central United States and adjacent southern
Canada and northern Mexico, south to the Gulf Coast (Gulf Coast
drainages from Mobile Bay in Georgia and Alabama to northern Mexico)
(Page and Burr, 2011); apparently not native to the Atlantic Slope.
Native to Canada, USA and Mexico (CABI, 2015a).
Native Range: Great Lakes, Hudson Bay, and Mississippi River basins
from New York to southern Saskatchewan and Montana, south to Gulf;
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Gulf Slope drainages from Mobile Bay, Georgia and Alabama, to
northern Mexico. Apparently not native to Atlantic Slope (Fuller and
Neilson, 2017a).
Ameiurus nebulosus:
Native to North America: Atlantic and Gulf Slope drainages from Nova
Scotia and New Brunswick in Canada to Mobile Bay in Alabama in
USA, and St. Lawrence-Great Lakes, Hudson Bay and Mississippi River
basins from Quebec west to Saskatchewan in Canada and south to
Louisiana, USA (Froese and Pauly, 2016).
Northamerica (CABI, 2015b)
Native Range: Atlantic and Gulf Slope drainages from Nova Scotia and
New Brunswick to Mobile Bay, Alabama, and St. Lawrence Great
Lakes, Hudson Bay, and Mississippi River basins from Quebec west to
southeastern Saskatchewan, and south to Louisiana. This species may
have been originally absent from all or part of the Gulf Coast west of the
Apalachicola and east of the Mississippi River. This speculation is based
on the very spotted distribution of the species both in panhandle Florida
and Alabama and the fact that it appears to be largely confined to
reservoirs in Alabama. In its native range in peninsular Florida it is
found primarily in larger bodies of water; Whereas, on the Atlantic Slope
in Florida, this species is found in both streams and sloughs (Fuller and
Neilson, 2017b).
Ameiurus natalis:
Native throughout most of the eastern and central USA and south eastern
Canada, maybe New Hampshire (where has been recorded as native
(Scarola, 1973; Scott and Crossman, 1973) but also as introduced (U.S.
Geological Survey, 2015).
Ameiurus natalis, a species of bullhead catfish, is native throughout most
of the eastern and central USA and south eastern Canada (CABI, 2009)
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Native Range: Atlantic and Gulf Slope drainages from New York to
northern Mexico, and St. Lawrence Great Lakes and Mississippi River
basins from southern Quebec west to central North Dakota, and south to
Gulf (Fuller and Neilson, 2017c).
Ameiurus catus:
Atlantic and Gulf Slope drainages from lower Hudson River, New York,
to Apalachicola basin in Florida, Georgia, and Alabama; south in
peninsular Florida to Peace River drainage (modified from Page and
Burr 1991).
Native Range: Atlantic and Gulf Slope drainages from lower Hudson
River, New York, to Apalachicola basin in Florida, Georgia, and
Alabama; South in peninsular Florida to Peace River drainage (Fuller
and Neilson, 2017c).
6. What is the global distribution of the
organism (excluding Europe)?
North and South America, Ameiurus melas:
Canada, Europa, Asia, Oceania, Introduced widely outside the native range. (Rose, 2006). Apart of
Pacific Islands
Europe, it has been introduced also in Chile (Welcomme, 1988; Froese
and Pauly, 2004), Mexico (Page and Burr, 1991; Froese and Pauly,
2004) and many states in the USA.
Ameiurus nebulosus:
It has been introduced outside of its native range in North America to
other areas of North America, Europe, Asia and Pacific islands (i.e. New
Zealand, Hawaii). Also Chile, Iran and Turkey (Salvador, 2015; Froese
and Pauly, 2016).
Ameiurus natalis:
Introduced into at least 14 states in the USA outside of its native range
(Fuller et al., 1999), in addition to southwestern British Columbia
(Hanke et al., 2006). Also it has been introduced in Mexico, as an
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aquaculture species (FAO, 1997).
7. What is the distribution of the organism in
Europe?
See
question
CHAPEAU.
1
of
Ameiurus catus
It was introduced in many states in USA (USGS, 2016), in Puerto Rico
(Erdsman, 1984) and Mexico (Comisión Nacional para el Conocimiento
y Uso de la Biodiversidad, 2016).
EU Ameiurus melas:
Widely distributed across Europe:
Austria, Germany, Bulgaria, Poland, Belgium, France, Italy, The
Netherlands, UK, Portugal, Spain, Croatia, Slovenia, Czech Republic,
Romania, Hungary, Slovakia, Denmark, Finland, Ireland, possible
Greece, Balkan countries, Albania and Turkey.
Ameiurus nebulosus:
Kottelat and Freyhof (2007) indicated that it is established in Germany,
Italy and Finland. Although (CABI, 2015b) mention that it is established
in many European countries, A. nebulosus has often been mistaken for A.
melas (See Rutkayová et al., 2012). The unclear taxonomic status of
both A. melas and A. nebulosus resulted in more doubts about the
occurrence of these species in some countries (Rutkayová et al., 2013).
Conversely, some authors consider it widely distributed across Europe:
from the Iberian Peninsula till the European part of Russia, Switzerand,
Turkia, Balkan countries and more recently in Greece (Barbieri, 2015)
Having in mind the possible mistakes already done with this species, we
found bibliography about its record in Belgium, Bulgaria, Netherlands,
UK (Olenin et al., 2008); Austria, Poland, Portugal, Spain, Italy, France,
Germany, Czech Republic (Froese and Pauly, 2016); Croatia, Slovenia
(Piria et al, 2016); Estonia, Ireland, Slovakia, Sweden (Secretariat of
NOBANIS, 2012); Bulgaria, Finland, Romania (GLOBAL INVASIVE
SPECIES, 2016); Luxembourg (Ries et al, 2014); Greece (Barbieri,
2015).
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Ameiurus natalis:
There are a number of reports of its introduction into Italy (Welcomme,
1988; Holcík, 1991). Gandolfi et al, 1991) also informed about the
occurrence of the yellow catfish in Italy. Thirteen years later the species
is confirmed as established in Italy (Elvira, 2001).
Ameiurus catus
UK (Britton and Davies, 2006); Poland (Nowak et al. 2008, 2010).
There is no information available about his spread to other countries, but
confusion between species could be possible, so identification of other
species in the genus as A. melas or A.nebulosus cannot be discarded.
8. Is the organism known to be invasive (i.e.
to threaten organisms, habitats or ecosystems)
anywhere in the world?
Yes
Except for Latvia, Letonia (not confirmed), Malta and Cyprus (no
information), in every European country at least one species of Ameiurus
has been introduced.
Ameiurus melas and A. nebulosus are recognized as succesfull invaders
in Europe (Invasive Species Specialist Group, 2009). Ameirus nebulosus
is included in the watch list of Belgium (Branquart, 2016).
Aquatic macroinvertebrates (mainly Chironomidae) dominated the black
bullhead´s diet in all size-classes and sites, irrespective of natural
riverine or artificial lentic habitats. Secondary prey items were
responsible for the observed between-sites (microcrustaceans in artificial
lentic habitat; oligochaeta and caddisfly larvae in natural riverine
habitats) and ontogenetic diet differences (from microcrustaceans to
larger prey). It consumed plant material, terrestrial prey and co-occurring
fish species (native or exotic) and thus they could be considered as
generalist or opportunistic, foraging on the most abundant and available
prey. It can negatively affect native (Iberian) ichthyofauna throughout
direct predation and competition (Leunda et al., 2008).
The fishery in North London had succumbed to a highly efficient
invader, A. melas, and the local angling club had lost one of their best
fisheries.
(https://marinescience.blog.gov.uk/2015/08/07/eradicating-blackbullhead-catfish/).
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The high flexibility in the life history of the black bullhead as
demonstrated by its non-native populations, as well as its extreme
tolerance and capability to live in systems with poor water quality,
suggests that this species has a high potential to invade new areas and
establish viable populations. (Novomeska and Kovac, 2009).
The great growth and life-history plasticity of black bullhead affords the
species great potential to invade and establish viable populations in new
areas. A species tolerant of pollutants, low dissolved oxygen (3.0 mg L1), and elevated water temperatures (up to 35 ºC) the black bullhead also
has a specialized, nest-guarding, reproductive strategy. Many of the
introduced fishes in Europe are nest-guarders, which suggests that black
bullhead has the potential to be highly invasive and exert impacts to
ecosystem function through increased turbidity (Copp et al., 2016)
Ameiurus nebulosus is a generalist omnivore, feeding mostly at night
and eating benthic organisms that occur frequently within freshwaters:
waste, molluscs, immature insects, terrestrial insects, leeches,
crustaceans, worms, algae, plant material, fishes and fish eggs (Scott and
Crossman, 1973). Young (30-60 mm total length) prefer chironomid
larvae, ostracods, amphipods, mayflies and other small aquatic
invertebrates (Scott and Crossman, 1973).
This omnivorous fish species can form very dense populations and is
able to dominate freshwater fish communities. Diet of large-sized
bullheads has been found to consist almost exclusively of juvenile
fishes. (Anseeuw et al., 2007).
For those reasons A. nebulosus is considered a pest in Poland, and
fisheries legislation forbids release of this species into the wild. (Nowak
et al, 2010).
The ecological effects of A. melas seem potentially close to the A.
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nebulosus (Nowak et al, 2010).
Several countries (Switzerland (Wittenberg, 2005); Poland (FAO, 1997);
Chile (Welcomme, 1988)) report adverse effects on native fish
communities following its establishment.
(http://www.cabi.org/isc/datasheet/94468)
Related to the distribution of brown bullhead, its decline in some
European countries, e.g. Belgium, Czech Republic and Poland, has
coincided with an increase in the distribution and abundance of black
bullhead in Central and Eastern Europe; these contrasting patterns have
led to suggestions that black bullhead is displacing brown bullhead.
However, the two species have overlapping native distributions so this
may simply be coincidental. However, further study is needed to
determine whether or not this is artifact or indicative of black bullhead
displacing brown bullhead (Copp et al., 2016)
Ameiurus natalis is known to eat minnows, crayfish, insects, and larvae
of insects, aquatic invertebrates, worms and more aquatic vegetation
(macroalgae) then the other bullheads.
The yellow bullhead was largely introduced in other North American
countries where it is not-native. At least one country reports adverse
ecological impact after introduction of Ameiurus natalis in North
America (Froese and Pauly, 2016)
Ameiurus catus
White catfish is apparently responsible for the disappearance of
Sacramento perch Archoplites interruptus in Thurston Lake, California
(McCarraher and Gregory, 1970).
Following the literature data, ictalurids are nocturnal zoophagophores,
consuming all animals in the water column whose size allows the species
to consume them. Besides invertebrates, among which insect larvae are
preferred, ictalurids feed on molluscs and fishes, as well as algae, plant
material and terrestrial invertebrates (Scott and Crossman, 1973;
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Brylinski and Chybowski, 2000; Kottelat and Freyhof, 2007; Leunda et
al., 2008; Ruiz-Navarro et al. 2014). Ameiurus species are predators of
small fishes and larvae that show identical microhabitat requirements
(Leunda et al., 2008).
Moreover, they are vectors of alien parasites (Scholz and Cappellaro,
1993; Uzunova and Zlatanova, 2007; Sheath et al., 2015).
In resume the bullheads could negatively affect native ichthyofauna
throughout direct predation and competition (Leunda et al, 2008).
The characteristics of a successful invader, well demonstrated for A.
melas and A. nebulosus could be met in the case of other species of
Ameiurus genus.
Collier and Grainger (2015) identify A. nebulosus with a high overall
risk in New Zealand.
In Japan is an uncategorized alien species and needs a detailed
investigation by the Japan Government before importation
(https://www.env.go.jp/nature/intro/4document/files/r_yunyu2.9_e.pdf).
9. Describe any known socio-economic
benefits of the organism in the risk
assessment area.
Fishing – low benefits
Low benefits in sport fishing and very low in pet trade.
As they are so tolerant to poor water conditions, the bullheads may
accumulate the pollutants in their bodies. Therefore, in some waters,
bullheads contain elevated levels of contaminants. The New York State
Department of Health has issued an advisory with recommendations for
limiting consumption of contaminated fish. So it seems that they no
longer represent an economic value.
Ameiurus melas:
Black bullhead (Ameiurus melas formerly Ictalurus melas), a species
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which is very close to brown bullhead (Ameiurus nebulosus), is farmed
in Italy in open farms (production in Italy for 2010 estimated in 250
tons) (EFSA, 2011).
Ameiurus nebulosus:
Economic benefits from aquaculture occur primarily within Chile, China,
Bulgaria and Belarus (Welcomme, 1988; Tan and Tong, 1989;
Reshetnikov et al., 1997; Mikhov, 2000), although the magnitude of
these benefits remains uncertain. Introduced populations of A.
nebulosus to Europe and some Pacific islands originally provided social
benefits as sportfish (Welcomme, 1988), but their current social value as
sportfish within their introduced range is low and has poor economic
value. Within their native range, the species may be held within zoos or
public aquariums (CABI, 2015b).
Ameiurus nebulosus is popular in some areas as a gamefish. Reportedly a
good eating fish, especially when smoked (Global Invasive Species,
2006).
Ameirus melas and Ameirus nebulosus is only a main species used in
aquaculture in Italy, and not in Slovenia or Croatia (Bianco and
Ketmaier, 2016).
Ameiurus natalis:
This species is of low economic importance as a food fish, stocking into
ponds, aquaculture and commercial aquarium trade. A. natalis is
extensively used as a laboratory animal for toxic chemicals and medical
experiments.
Ameiurus natalis is considered good to eat and may be sought by some
fishermen. It is of low economic importance as a food fish, stocking into
ponds, aquaculture and commercial aquarium trade. A. natalis is
extensively used as a laboratory animal for toxic chemicals and medical
experiments (CABI, 2009).
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The yearly European aquaculture production and value of Black bullhead
Ameiurus melas (average of 2000–2004) is in the ninth position (473.4
tons; 1,770.7 thousands US$; 3.74 US$ kg–1) (Turchini et al, 2008).
In European inland aquaculture, there are American native finfish
species supporting a relatively good production (1,292 tons/year in the 5year period 2000–2004) (Turchini et al., 2008).
The impacts of aquaculture on biodiversity and particularly the
utilization of alien species for culture purposes are of current and
increasing concern, and the consequences of decreasing or changing
biodiversity are well known to be potentially devastating. It has been
speculated that the presence of alien fish can be a reliable indicator of
river health and therefore the wellbeing of European inland waters can
be considered to be at high risk (Turchini et al., 2008).
Variable results have been accomplished by species introductions,
depending on the species and geographic area. Only a few finfish species
are generally recognized as beneficial from a socio-economic viewpoint,
usually by improving fishing or aquaculture opportunities. In natural
waters, the introductions have resulted in many cases in economically
profitable fisheries, although most introductions have failed or led to
unwanted consequences in the form of reduced or collapsed native fish
stocks (Turchini et al., 2008).
Bullfish are not between the species that historically dominated the
European aquaculture and that nowadays they don’t represent an
alternative to the almost unprofitable rainbow trout and carp farming. At
the same time, in recent years, in the complex panorama of European
inland aquaculture, the appearance of new exotic species for culture
purposes should be considered with concern (Turchini et al., 2008).
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SECTION B – Detailed assessment
PROBABILITY OF ENTRY
Important instructions:
 Entry is the introduction of an organism into Europe. Not to be confused with spread, the movement of an organism within Europe.
 For organisms which are already present in Europe, only complete the entry section for current active pathways of entry or if relevant potential future
pathways. The entry section need not be completed for organisms which have entered in the past and have no current pathways of entry.
QUESTION
RESPONSE
[chose one entry,
delete all others]
1.1. How many active pathways are relevant to the
potential entry of this organism?
Aquaculture,
fisheries …
(If there are no active pathways or potential future
pathways respond N/A and move to the Establishment
section)
CONFIDENCE COMMENT
[chose one
entry, delete all
others]
low
Introductions of black bullhead have historically been
for either aquaculture, recreational fishing or as an
ornamental species. In European waters, the dispersal
mechanism is not clear but spread could be as a result of
accidental and illegal introductions or natural dispersion
between countries via watercourses (CABI, 2015a)
A. nebulosus was likely spread primarily for
recreational angling opportunities. Its spread has been
undoubtedly facilitated by its ability to survive low
oxygen concentrations for prolonged periods. Its
establishment, once introduced, was likely assisted by
its generalist, omnivore diet with feeding aided, even in
turbid waters, by its chin barbels (CABI, 2015b)
Results based on the morphological characters
confirmed the occurrence of A. melas for the first time
in the Czech republic freshwaters. In terms of A. melas
origin (in case of the Czech Republic), the most
probable explanation for its finding in the Lužnice River
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floodplain might be natural spread of individuals from
pond aquaculture, via e.g. pond connecting canals.
Thus, it seems likely that A. melas was accidentally
imported amongst carp (Cyprinus carpio L.) or tench
(Tinca tinca L.) from countries where it already widely
occurs, such as Hungary or Romania (Wilhelm, 1998.
In: Musil et al, 2008).
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PROBABILITY OF ESTABLISHMENT
Important instructions:
 For organisms which are already well established in Europe, only complete questions 1.15 and 1.21 then move onto the spread section. If uncertain,
check with the Non-native Species Secretariat.
QUESTION
1.15. How widespread are habitats or species necessary
for the survival, development and multiplication of the
organism in Europe?
RESPONSE
widespread
CONFIDENCE
high
COMMENT
Ameriurus melas inhabits in irrigation channels, lakes,
ponds and reservoirs are the principal habitats. Rivers and
streams are secondary habitats (CABI, 2015a)
Black bullhead is classed as a warm-water species, and in
its native range, the species is found in the downstream
sections of smallto-medium-sized streams of low gradient,
ponds and backwaters of large rivers and silty, soft
bottomed areas of lakes and impoundments. Black
bullhead are said to be most abundant in smaller water
bodies, especially artificial and heavily managed ponds
(Copp et al, 2016).
This demersal species inhabits slow-flowing habitats
(limnophilic) with soft substrata in all riverine and
lacustrine environments, including artificial ones such as
ponds and reservoirs (Leunda et al., 2008), with an
opportunistic dietary.
Previous research on black bullhead suggests that it is
highly tolerant to environmental degradation and is
capable of living with poor water quality conditions
(Ribeiro et al. 2008).
One of the greatest concerns in the case of the black
bullhead, is associated with degraded or impacted
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ecosystems, which are considered more susceptible to
invasion (Moyle, 1986). This facilitates invasions by
species such as the black bullhead (Hanchin et al. 2002),
which have been found to benefit in growth terms from
increasing eutrophication. Indeed, all of these factors
contribute to the black bullhead’s potential as a successful
invader (e.g. Gante and Santos 2002; Koščo et al. 2004;
Dextrase and Mandrak, 2006).
Black bullhead has a great potential to invade and establish
viable populations in new areas, and this is facilitated by
life-history plasticity. However, the risk posed by black
bullhead will vary according to local environmental
conditions, and this is apparent in the FISK rankings of
this warm-water species, which is perceived in the north of
Europe (Finland) as posing a lower risk of becoming
invasive than in countries of intermediate or lower
latitudes.
Across Europe, numerous dams were constructed for river
regulation and as hydropower plants, which lead to water
flow lag. Since black bullhead inhabits soft substrates of
sluggish sections of creeks and rivers, as well as
backwaters, channels, swamps and impoundments, this
was excellent opportunity for further expansion of its
range (Cvijanovic et al., 2008).
Ameiurus nebulosus inhabits brackish waters and estuaries
are secondary habitats as irrigation channels. Principal
habitats are lake, ponds, reservoirs, rives and streams
(CABI, 2015b).
Ameiurus natalis inhabits irrigation channels, lakes, ponds,
reservoirs rivers and streams (CABI, 2015c).
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Suitable habitats are present and widely distributed in the
Risk Assessment Area for Ameiurus spp.
1.21. How likely is it that biological properties of the
organism would allow it to survive eradication campaigns
in Europe?
very likely
high
Ameiurus melas
As compiled in Nowak et al (2010), Ameiurus melas is a
typical limnophilic and one of the most tolerant fish
species capable of resisting water pollution (Ribeiro et al.,
2008). Due to their high fecundity and ecological
plasticity, both A. melas and A. nebulosus are considered
invasive species.
The black bullhead has several characteristics associated
with successful invaders (Ribeiro et al., 2008), such as
high reproductive potential, parental care, opportunistic
feeders, aggressive behaviour and considerable tolerance
to water pollution, turbidity, low oxygen concentration,
elevated temperatures and a range of pH values
(Novomeská et al., 2013). Its spread has been undoubtedly
facilitated by its ability to survive low oxygen
concentrations for prolonged periods (Scott and Crossman,
1973).
Ameiurus nebulosus
Once introduced, A. nebulosus is easy to establish thanks
to its generalist, omnivore diet, even in turbid waters,
assisted by its chin barbels (Scott and Crossman, 1973).
Conversely, its stout shape and strong dorsal and pectoral
fin spines would minimize predation by native predators.
Its parental care of eggs and young would also reduce
mortality in the young (Scott and Crossman, 1973).
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It is nearly impossible to eradicate them when it is
established in a river. In small, closed waters (e.g. small
lakes or ponds), control could be possible.
In a fishery in North London the black bullhead have
spread, the risk to the wider environment was significant;
so a piscicide based eradication was carried out by the
National Fisheries Services Virtual Non-native Species
Management Team in May 2014. It seems they managed
to remove the only known population of the highly
invasive black bullhead from a fishery in Essex, England
(https://marinescience.blog.gov.uk/2015/08/07/eradicating
-black-bullhead-catfish/).
As compiled in Nowak et al (2010), Ameiurus melas is a
typical limnophilic and one of the most tolerant fish
species capable of resisting water pollution (Ribeiro et al.,
2008). Due to their high fecundity and ecological
plasticity, both A. melas and A. nebulosus are considered
invasive species (Gante and Santos, 2002; Koščo et al.,
2004; Dextrase and Mendrak, 2006).
The black bullhead has several characteristics associated
with successful invaders (Ribeiro et al., 2008), such as
high reproductive potential, parental care, opportunistic
feeders, aggressive behaviour and considerable tolerance
to water pollution, turbidity, low oxygen concentration,
elevated temperatures and a range of pH values
(Novomeská et al., 2013). Its spread has been undoubtedly
facilitated by its ability to survive low oxygen
concentrations for prolonged periods (Scott and Crossman,
1973).
The characteristics of successful invaders are common to
at least four of the species of Ameiurus, so we can affirm
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that biological properties of the genus would allow it to
survive eradication campaigns in Europe.
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PROBABILITY OF SPREAD
Important notes:
 Spread is defined as the expansion of the geographical distribution of a pest within an area.
QUESTION
RESPONSE
CONFIDENCE
COMMENT
2.1. How important is the expected spread of this
organism in Europe by natural means? (Please list and
comment on the mechanisms for natural spread.)
major
high
Once established in a basin it is to expect a natural
expansion in it. It has several characteristics common to
successful invaders, which increases their invasive potential.
A. melas and A. nebulosus can tolerate poor river conditions,
wide temperature tolerance and a lack of native competitors
and predators can facilitate their range expansion along
Europe.
Ameiurus melas
In European waters, the dispersal mechanism is not clear but
spread of A. melas could be as a result of accidental and
illegal introductions or natural dispersion between countries
via watercourses (CABI, 2015a)
The black bullhead occurred (imported for aquaculture) in
Europe, at first, in France (1871) (Coucherousset et al.,
2006). The species expanded relative slowly, however
nowadays this is the most widespread North American
ictalurid catfish in Europe (Pedicillo, 2008). The expansion
was human helped in some cases, while in other situations, a
slow, self – managed spreading was observed: for example
in Spain (first recorded in 1984 (Elvira 1984) and Portugal
(first recorded in 2002 (Gante and Santos 2002).
Black bullhead (Ameiurus melas) was introduced to a
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western Hungarian fish culture in the beginning of the
1980s, and escaped specimens spread rapidly along the
Danube. Abundant stocks have developed in most of the
backwaters along the Danube (Bódis et al., 2012).
The species will undoubtedly increase its introduced range
through natural dispersal within drainage networks. The
magnitude of spread will be dependent upon the spatial
configuration of potential habitats and their connectivity via
drainage networks. Most natural dispersal within the native
range of Canada and the USA has occurred at local levels
(Fuller et al., 1999).
Ameirus nebulosus
In European waters, the dispersal mechanism is not clear but
spread could be as a result of accidental and illegal
introductions or natural dispersion between countries via
watercourses (Nowak et al., 2010; Copp et al., unpublished).
Recently, in Greece, a self-sustained population of A.
nebulosus was discovered and is supposed that the fish was
introduced from Bulgaria through the transboundary waters
of the Strymon River (Barbieri, 2015).
It is to be noted that once the species reached the Danube
River, the Rhine-Main-Danube Canal offers no physical
barrier to the spreading of this invasive species to Western
Europe (Müller et al., 2002).
The black bullhead occurred (imported for aquaculture) in
Europe, at first, in France (1871) (Coucherousset et al.,
2006). The species expanded relative slowly, however
nowadays this is the most widespread North American
ictalurid catfish in Europe (Pedicillo, 2008). The expansion
was human helped in some cases, while in other situations, a
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
slow, self – managed spreading was observed: for example
in Spain (first recorded in 1984 (Elvira 1984) and Portugal
(first recorded in 2002 (Gante and Santos 2002).
The species will undoubtedly increase its introduced range
through natural dispersal within drainage networks. The
magnitude of spread will be dependent upon the spatial
configuration of potential habitats and their connectivity via
drainage networks. Most natural dispersal within the native
range of Canada and the USA has occurred at local levels
(Fuller et al., 1999).
European introductions of A. nebulosus occurred
concurrently, with individuals from North America
introduced to Germany for angling, sport and aquaculture in
1885 (Scott and Crossman, 1973), leading to subsequent
intentional and unintentional secondary spread to the rest of
Europe. A. nebulosus is a moderately strong swimmer (Scott
and Crossman, 1973) that is capable of surviving degraded,
warmwater freshwater environments; therefore, the species
will undoubtedly increase its introduced range through
natural dispersal within drainage networks. The magnitude
of spread will be dependent upon the spatial configuration
of potential habitats and their connectivity via drainage
networks. Most natural dispersal within the native range of
Canada and the USA has occurred at local levels (Fuller et
al., 1999).
Ameiurus nebulosus is a moderately strong swimmer that is
capable of surviving degraded, warmwater freshwater
environments; therefore, the species will undoubtedly
increase its introduced range through natural dispersal
within drainage networks. The magnitude of spread will be
dependent upon the spatial configuration of potential
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
habitats and their connectivity via drainage networks. Most
natural dispersal within the native range of Canada and the
USA has occurred at local levels.
A. natalis are sedentary fish which may disperse naturally
over short distances (CABI, 2009).
2.2. How important is the expected spread of this
organism in Europe by human assistance? (Please list and
comment on the mechanisms for human-assisted spread.)
moderate
medium
The species in this genus was likely spread primarily for
recreational angling opportunities.
The intentional stocking of A. melas for recreational fishing
purposes has reduced in recent years. In Czech Republic,
quite recently, evidence was obtained on unintentional
introduction of Ameiurus melas with carp stock from
Croatia to the fishponds in the Třeboň district in 2003
(Koščo et al. 2004; Lusk et al, 2010). The expansion was
human helped in some cases, for example it was imported to
Hungary from Italy in 1980 (Harka 1997).
A.nebulosus was first introduced in the Pacific islands
(1877) with the release of 100-200 individuals for angling in
Auckland, New Zealand. These introductions resulted in
local viable populations by 1885 (Holcík, 1991). Additional
introductions for angling and sport occurred in Hawaii in
1893 (Welcomme, 1988).
The intentional stocking of A. melas for recreational fishing
purposes has reduced in recent years. In Czech Republic,
quite recently, evidence was obtained on unintentional
introduction of Ameiurus melas with carp stock from
Croatia to the fishponds in the Třeboň district in 2003
(Koščo et al. 2004; Lusk et al, 2010). The expansion was
human helped in some cases, for example it was imported to
Hungary from Italy in 1980 (Harka 1997).
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
Although angling for A. nebulosus within Canada is
relatively unpopular (Scott and Crossman, 1973), the initial
introduction to Europe and the Pacific islands for angling
suggests almost global popularity as a sportfish; therefore,
unauthorized introductions for angling purposes may occur.
The Brown bullhead (Ameiurus nebulosus) was introduced
to Hungary in 1902 and rapidly spread in natural waters
because of stockings for recreational reasons (Bódis et al.,
2012).
There have been intentional and unintentional,
human‐mediate species introductions. Fishes are dispersed
beyond their native ranges because they are interesting
sporting species, for example, Ameiurus used in aquaculture
(Bianco and Ketmaier 2016).
Introduction via fisheries (angling/sport purposes) and
aquaculture are the dominant long-distance (national;
international) vectors. Intentional introductions by fisheries
managers may result in long-distance travel events via
stocking from source populations. Aquaculture introductions
may have similar magnitudes of spread. For example, China
(Beijing and Hubei province) stocked A. nebulosus for
aquaculture purposes from USA broodstock. Unauthorized
introductions by anglers also has the potential to contribute
to local, national or international events but may be
constrained by the effectiveness of certain legal restrictions
that prohibit import of live organisms across borders (CABI,
2015b).
The natural expansion of the Brown bullhead (Ameiurus
nebulosus) was assisted by intentional introductions carried out
by angling associations, fish pond´s owners, accidental
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
admixture to the stocking material of the other species and
using it as a live bait (Hanel et al., 2011).
Intentional stocking has been reported in case of A. natalis
as this species can be introduced into degraded watercourse
due to their high tolerance to pollution (Klossner, 2005).
Ameiurus natalis is easy to identifty in shipments of tropical
fish and fish to be stocked for anglers and is therefore
unlikely to be accidentially introduced into new areas.
A. natalis have been intentionally introduced in new
waterways by several pathways, including releases from
aquariums and intentional stocking in open waters for food
and game fish (CABI, 2009).
Ameiurus catus
Accidental movement of either their eggs or larvae via
anglers’ nets is believed to be the mechanism by which
Ameiurus catus may be released (Zięba et al., 2010).
Some countries have forbidden new entries of A. melas and
A. neboulosus (France, Poland etc), so we consider that
human-assisted spread will become less important.
In conclusion the spread by natural means could be more
important that by human assistance.
2.3. Within Europe, how difficult would it be to contain
the organism?
very difficult
high
Once established in a river basin, the bullheads´ control is
almost impossible.
The application of trapping and electric fishing to
controlling black bullhead Ameiurus melas was relatively
effective in a French lake as no compensatory responses
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
were recorded. In contrast, compensatory responses were
detected in A. melas populations elsewhere following mass
removals.
Thus, where the management aim is suppression of invasive
fish populations, then removals can provide an effective
short-term measure. Its long-term effectiveness is, however,
reduced substantially if the remaining fish exhibit
compensatory responses, such as increased survival, growth
and fecundity. Correspondingly, long-term population
suppression using removals is likely to require sustained
management efforts, potentially accruing high resource
costs (Davies and Britton, 2015).
Control of A. melas populations within lentic environments
is possible. The results of Louette and Declerck (2006)
study on “Assessment and control of non-indigenous brown
bullhead (Ameiurus nebulosus) populations using fyke nets
in shallow ponds” suggest that double fyke nets, when
combined with the mark-recapture technique, are a very
useful tool for the efficient and reliable assessment of brown
bullhead populations. The results of the study also suggest
that double fyke nets may potentially be a cost-effective tool
for the mass removal of non-indigenous brown bullhead
populations. This could be applied also for other species of
Ameiurus. Other method that worked was using a piscicide
to extirpate an established stillwater population from
England in 2014 (see 2.14 for further information).
Ameiurus melas
In a fishery in North London the black bullhead have
spread, the risk to the wider environment was significant; so
a piscicide based eradication was carried out by the National
Fisheries Services Virtual Non-native Species Management
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
Team in May 2014. It seems they managed to remove the
only known population of the highly invasive black bullhead
from
a
fishery
in
Essex,
England
(https://marinescience.blog.gov.uk/2015/08/07/eradicatingblack-bullhead-catfish/).
In England it has been completed an eradication of the only
known wild population of black bullhead catfish in England
(Essex). In a one day operation, specially trained officers
treated the lake with rotenone, a chemical that targets fish,
whilst causing little harm to other aquatic life. The work
was successful in removing this highly invasive and
damaging species. The lake and its native fish had been
suffering the impacts of these catfish for some time and
angling club members had noticed a drastic decline in the
performance of the fishery; including the deterioration in the
growth rate, size of native fish, reduced catch rate and the
black bullhead as a nuisance. The club contacted the
Environment Agency fisheries department and the operation
to remove the catfish was planned.
Eradication through piscicides, such as rotenone or through
mechanical removal by fishing/angling; the species is
reportedly easy to catch. Mass removal has also been
considered as a possibility (CABI, 2015a)
Ameiurus nebulosus
Eradication may involve the use of chemical agents (e.g.,
rotenone) to induce mortality within introduced populations,
although such methods should be evaluated for their
potential effects on non-target fishes. Other measures (e.g.,
physical removal using fish sampling gears: fyke nets,
seines, boat and backpack electrofishers) may also be
effective.
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
Physical control should involve, if possible, physical
isolation of introduced populations, which may require
physical (e.g., block nets) or electrical barriers.
Biological control of adult A. nebulosus is unlikely given the
paucity of natural predators within the native range,
although juveniles may be predated upon by certain largebodied fishes (e.g., Esox spp. within native range) (CABI,
2015b).
Ameirus melas and Ameiurus nebulosus is difficult/costly to
control (CABI, 2015a).
Ameiurus natalis
Public awareness is essential for this species to prevent
misidentification of this species with A. melas and A.
nebulosus. Public awareness is important to prevent
establishment of new populations and to prevent further
illegal introductions of this species.
Open season fishing for A. natalis is possible and fish can be
readily caught using a regular line, by electrofishing or a
beach seine. Targeted removal of the young-of-the-year
when in tight schools would limit the impact this species has
on the habitat.
Chemicals such as rotenone can be applied at a
concentration of three parts per million to remove A. natalis
but will also eliminate any other fish which you may want to
protect. (CABI, 2009).
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2.4. Based on the answers to questions on the potential for
establishment and spread in Europe, define the area
endangered by the organism.
[Most of
Europe]
high
At least 2 species of the genus Ameiurus are established in
Europe, A. nebulosus and A. melas, the latter being present
in almost all countries. Other 2 (A. natalis and A. catus)
have been eventually recorded.
See answers to questions 5 and 6 of EU CHAPPEAU
2.5. What proportion (%) of the area/habitat suitable for
establishment (i.e. those parts of Europe were the species
could establish), if any, has already been colonised by the
organism?
33-67
low
Given the high proportion of countries where Ameiurus
species are established, as well as the possible bad
ecological conditions of the habitats where it is found, it is
considered that it may be of the order of that proportion.
2.6. What proportion (%) of the area/habitat suitable for
establishment, if any, do you expect to have been invaded
by the organism five years from now (including any
current presence)?
10-33
low
Given the recent colonization of the species it is estimated
that its colonization in five-years from now may be of this
order. The life-history traits of A. melas and A. nebulosus
and their plasticity are similar to other successful invaders,
which will facilitate range expansion for this species. It is
supposed that, if no measures will be taken, other Ameiurus
species could have the same success as invaders. Wide
environmental tolerances and the fact that suitable habitats
are present and widely distributed in the Risk Assessment
Area, will also allow a greater number of water bodies to
provide suitable habitat for Ameiurus.
2.7. What other timeframe (in years) would be appropriate
to estimate any significant further spread of the organism
in Europe? (Please comment on why this timeframe is
chosen.)
20
low
There is not a follow-up of its expansion, but considering
the conditions of expansion in which the species occurs, this
can be significant in this period.
As included in the article Fishes of the genus Ameiurus
(Ictaluridae, Siluriformes) in the Transcarpathian water
bodies (Movchan et al, 2014) their expansion in Tisza took
place subsequently after almost 50 years, and now there is a
new destabilization (deterioration and redistribution) in
some ichthyocenoses under the influence of dangerous and
aggressive A. nebulosus and A. melas. A. nebulosus
gradually became a “victim” of A. melas.
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
In the case of A. natalis its occurrence in Italy was
confirmed in 1988 (Welcomme). So, only thirteen years
later the species is confirmed as already established. (Elvira,
2001).
It is to be noted that nowadays the aquatic ecosystems are
subject to more deterioration, eutrophication and loss of
biodiversity that transform habitats in more suitable for
Ameiurus spp.
2.8. In this timeframe what proportion (%) of the
endangered area/habitat (including any currently occupied
areas/habitats) is likely to have been invaded by this
organism?
10-33
low
2.9. Estimate the overall potential for future spread for
this organism in Europe (using the comment box to
indicate any key issues).
high
medium
In Spain (Dana et al., 2016) cited the arrival of A.melas at
Majalberraque stream probably due to the natural dispersion
that takes advantage of the connection of the rice paddy
system and its network of canals with the Guadalquivir. The
locality of the Brazo del Este cited by García-de Lomas et
al. (2009) is more than 20 kilometers downstream of that,
which confirms its dispersion on the Guadalquivir River. It
is also very likely that the species is much more widespread
in the province of Seville.
There is no information about the endangered areas/habitats
occupied by the species, but given the endangered situation
of the habitats in the river basins in Europe, it is estimated
that it could be of the order of this proportion.
As compiled in the document Status of Non-Indigenous Fish
Species
in
the
Balaton
Catchment
(http://www.eulakes.eu/upload/eulakes/gestionedocumentale
/output%205.2.1%20%20lake%20Balaton_effects%20of%20climate%20change
%20on%20new%20species_784_2181.pdf) the species
expanded relative slowly, however nowadays A. nebulosus
and A. melas are the most widespread North American
ictalurid catfish in Europe (Pedicillo, 2008). The expansion
was human helped in some cases, for example A. melas was
44
EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
imported to Hungary from Italy in 1980 (Harka, 1997). In
other situations, a slow, self – managed spreading was
observed: for example in Spain_ first recorded in 1984
(Elvira 1984) and Portugal- first recorded in 2002 (Gante
and Santos, 2002). The bullheads are tolerant of the harsh
water conditions (eg. water pollution, low dissolved oxygen
levels), omnivorous, aggressive, has parental care and
prolonged reproduction period (Braig and Johnson, 2003,
Novomenska and Kovac, 2009, Scott and Crossman, 1973).
In Hungarian waters it seems that A. melas outcompete the
congener brown bullhead (Ameiurus nebulosus) (Harka and
Sallai, 2004), this phenomenon is prominent either in the
Balaton catchment.
Based on its high flexibility in its life-history traits of A.
melas and A. nebulosus, one may assume that the bullheads
have a great potential to spread into new environments
(Novoneska et al., 2010).
Ameiurus melas is abundant in its native range, capable of
securing and ingesting a wide range of food, gregarious, it
has a broad native range, it has high reproductive potential,
it’s highly adaptable to different environments, it’s invasive
in its native range, it is a habitat generalist, it has been
proved invasive outside its native range, it’s tolerant of
shade (CABI, 2015a)
Ameiurus nebulosus is abundant in its native range, capable
of securing and ingesting a wide range of food, fast
growing, it has a broad native range, it has high genetic
variability, it has high reproductive potential, it’s highly
adaptable to different environments, it’s highly mobile
locally, it is a habitat generalist, it’s pioneering in disturbed
areas,it has been proved invasive outside its native range, it
tolerates, or benefits from, cultivation, browsing pressure,
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
mutilation, fire etc (CABI, 2015b).
Ameiurus natalis is abundant in its native range, capable of
securing and ingesting a wide range of food, it has a broad
native range, it’s highly adaptable to different environments,
it’s highly mobile locally, it’s a habitat generalist (CABI,
2009).
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PROBABILITY OF IMPACT
Important instructions:
 When assessing potential future impacts, climate change should not be taken into account. This is done in later questions at the end of the assessment.
 Where one type of impact may affect another (e.g. disease may also cause economic impact) the assessor should try to separate the effects (e.g. in this
case note the economic impact of disease in the response and comments of the disease question, but do not include them in the economic section).
 Note questions 2.10-2.14 relate to economic impact and 2.15-2.21 to environmental impact. Each set of questions starts with the impact elsewhere in
the world, then considers impacts in Europe separating known impacts to date (i.e. past and current impacts) from potential future impacts. Key words
are in bold for emphasis.
QUESTION
RESPONSE
CONFIDENCE
COMMENTS
2.10. How great is the economic loss caused by the
organism within its existing geographic range, including
the cost of any current management?
Moderate
Low
There are no studies where this issue had been
calculated.
The Ameirurus spp has the potential to hinder local
commercial and sport fisheries through competition
with target species.
Global data are no available but in UK the eradication
of Ameiurus melas has been developed in a fishery.
(http://www.nonnativespecies.org/news/index.cfm?id=1
51). A fishery in North London succumbed to this
highly efficient invader, and the local angling club had
lost one of their best fisheries. The operation to remove
the catfish costed approx. £5000.00 (€6356.00)
£10,000.00, including manpower costs (APHA,
personal comm.).
There is potential that Ameiurus melas can have a
negative economic impact on communities as this fish
can be a 'nuisance' species taking lines/bait intended for
other species. Anglers not targeting this species might
therefore move on to black bullhead free waters taking
not only the money from recreational fishing but
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
tourism (food, accommodation and transportation) all of
which may provide economic opportunities locally
(CABI, 2015a).
To date, economic impacts resulting from A. nebulosus
introductions have not been quantified. In certain cases
of wild establishment, A. nebulosus introductions have
the potential to hinder local commercial and sport
fisheries through competition with target species
(CABI, 2015b).
Van der Veer and Nentwig (2014) don’t find any
environmental economic impact of A. melas and A.
nebulosus in six environmental and six economic
impact categories agriculture, animal production,
forestry, human infrastructure, human health and human
social life.
2.11. How great is the economic cost of the organism
currently in Europe excluding management costs (include
any past costs in your response)?
Unknown
To
date,
economic
impacts
resulting
from Ameiurus introductions have not been quantified.
In certain cases of wild establishment, A. nebulosus and
A. melas introductions have the potential to hinder local
commercial and sport fisheries through competition
with target species.
For instance A. melas was included in the list of 12
aquatic species potentially causing greatest ecological
and economic harm in Great Britain and Ireland
(Gallardo and Aldridge, 2013).
Species with high potential impact on water quality as
Ameiurus melas are not necessarily those associated
with monetary costs (e.g. Neovison vison) with could be
more conspicuous for general public.
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
2.12. How great is the economic cost of the organism
likely to be in the future in Europe excluding management
costs?
Unknown
Further studies should be undertaken in relation with
water quality.
In the Alqueva Dam their evaluation of both
environmental management programmes, and various
studies from the region, brought to light a number of
underevaluated impacts. It was identified that the
transition from flowing to standing water catalyzed the
emergence of invasive fish and plant species (Ameiurus
melas,
Eichhornia
crassipes,
etc.).
http://ced.berkeley.edu/downloads/research/AlquevaRe
portLA205-2015.pdfIn the absence of data for this species, costs for the
control of other species of fish are included in an
indicative way:
- Current efforts to control topmouth gudgeon in GB
amount
to
£190,000
over
4
years
(http://invasivespeciesireland.com/wpcontent/uploads/2010/07/Economic_Impact_Assessmen
t_FINAL_280313.pdf)
- In 2010 alone, the US federal government committed
$78.5 million in investments to prevent the introduction
of Asian carp to the Great Lakes, where they would
threaten Great Lakes fisheries and could negatively
impact remaining populations of endangered or
threatened
aquatic
species.
(https://www.fws.gov/verobeach/PythonPDF/CostofInv
asivesFactSheet.pdf).
2.13. How great are the economic costs associated with
managing this organism currently in Europe (include any
past costs in your response)?
Unknown
There are no published studies, other than the work
undertaken by the Environment Agency’s Non-native
Species Eradication Team (See Comment for Question
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
1.21 and 2.14)
The results of Louette and Declerck (2006) study on
Assessment and control of non-indigenous brown
bullhead (Ameiurus nebulosus) populations using fyke
nets in shallow ponds suggest that double fyke nets,
when combined with the mark-recapture technique, are
a very useful tool for the efficient and reliable
assessment of brown bullhead populations. The results
of the study also suggest that double fyke nets may
potentially be a cost-effective tool for the mass removal
of non-indigenous brown bullhead populations. This
could be applied also for other species of Ameiurus.
As included in the “Ecological risk assessment of nonindigenous species in Lake Balaton: a pilot study”
(http://eulakes-model.eu/media/files/ecological-riskassessment-of-non-indigenous-species-in-lakebalaton.pdf) the FISK assessments were undertaken
independently by the three co-authors. Each person
calculated the total FISK scores for each species.
Altogether nine species (Carassius gibelio; Perccottus
glenii; Anguilla anguilla; Lepomis gibbosus; Neogobius
fluviatilis; Gambusia holbrooki; Hypophthalmichtys
molitrix x nobilis; Ameiurus melas; Pseudorasbora
parva). 5 of the 9 examined fish species (55.6%) –
among of them Ameiurus melas- received FISK scores
≥19 (scores between 24 and 33), and thus could be
classified as species posing high risk to become
abundant in the Balaton catchment. For 6 species
(among of them Ameiurus melas), effect on the
Catchments seemed to be more significant, which could
mean the hardly quantifiable costs of ecosystem
services (Farber et al., 2002).
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2.14. How great are the economic costs associated with
managing this organism likely to be in the future in
Europe?
Unknown
2.15. How important is environmental harm caused by the
organism within its existing geographic range excluding
Europe?
major
There are no specific studies.
Population suppression, or even removal with sufficient
effort, is possible through bio-manipulation of A. melas
populations using fyke nets (Louette and Declerck,
2006)
medium
The ecological effects of A. melas seem potentially
close to the A. nebulous.
Introduced Black Bullhead eat endangered humpback
chubs Gila cypha in the Little Colorado River, and may
exert a major negative effect on the population there
(Marsh and Douglas 1997. In Fuller P. and Neilson M.,
2017). Minckley (1973), in Fuller P. and Neilson M.
(2017) reported that this species is generally considered
a pest in Arizona as it forms large stunted populations
that compete with more desirable fishes for space and
food. Black Bullheads are voracious predators of newly
hatched gamefish (Whitmore, 1997. In Fuller P. and
Neilson M., 2017). Introduced predatory fishes,
including the Black Bullhead, are likely at least partially
responsible for the decline of the Chiricahua leopard
frog Rana chiricahuensis in southeastern Arizona
(Rosen et al. 1995), and have been shown to reduce the
abundance and diversity of native prey species in
several Pacific Northwest rivers (Hughes and Herlihy
2012. In Fuller P. and Neilson M., 2017).
Van der Veer and Nentwig (2015) find some
environmental impacts in herbivory, predation,
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
competition, disease transmission, and ecosystem
alteration) of A. melas and A. nebulosus mainly in
competition, predation, ecosystem alteration, herbivory
and disease transmission.
CABI (2015a) points out the following impacts of
Ameiurus melas. The main mechanism is predation. The
main outcomes are: conflict, damaged ecosystem
services, ecosystem change/ abitat alteration,
modification of natural benthic communities,
modification of nutrient regime, negatively impacts,
aquaculture/fisheries, reduced native biodiversity, threat
to/loss of endangered species and threat to/ loss of
native species.
CABI (2015a) points out the following impacts of
Ameiurus nebulosus: The main mechanisms are
competition – monopolizing resources, interaction with
other invasive species and predation. The main
outcomes are altered trophic level, damaged ecosystem
services, ecosystem change/habitat alteration, and
modification of natural benthic communities, negatively
impacts
aquaculture/fisheries,
reduced
native,
biodiversity, threat to / loss of endangered species and
threat to / loss of native species.
Global Invasive Species (2006) doesn’t find any hard
evidence of environmental impacts caused by these
brown bullheads, although there is some concern that
may negatively affect trout fisheries, freshwater
crayfish and eels.
White Catfish were apparently responsible for the
disappearance of Sacramento perch Archoplites
interruptus in Thurston Lake, California (McCarraher
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and Gregory 1970. In: Fuller P. and Neilson M. 2017)
CABI (2009) points out the following impacts of
Ameiurus nativis: Ecosystem change/ habitat alteration,
modification of natural benthic communities, negatively
impacts aquaculture/fisheries, negatively impacts
tourism, reduced amenity values, reduced native
biodiversity and threat to/ loss of native species.
2.16. How important is the impact of the organism on
biodiversity (e.g. decline in native species, changes in
native species communities, hybridisation) currently in
Europe (include any past impact in your response)?
major
medium
Ameiurus natalis is partially responsible for the decline
of the Chiricahua leopard frog (Rana chiricahuensis) in
southeastern Arizona (Rosen et al., 1995; Fuller et al.,
1999).
Ameiurus nebulosus has negative effects on native fish
species by feeding on the bottom fauna, small fishes,
fish larvae, and roe (Pujin and Sotirov, 1966).
Of the European countries where Ameiurus melas has
been introduced, four of them reported impacts on the
ecological community due to dominance, three reported
bioaccumulation of pollutants, two reported impacts due
to competition (for food or/and for space) with native
species, and one reported impacts due to predation on
native species. There may also be impacts (direct or
indirect) through increased turbidity related to reduced
macrophyte growth and reduced stability of substrates
(Hubble, 2011).
The bullheads should be considered generalist, foraging
on the most abundant and available prey. The impact is
because of the competition, due to the coincidences
with the preys used by some native species, predation
over native species and habitat degradation (Leunda et
al, 2008).
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As compiled in CABI (http://www.cabi.org/isc/),
impacts produced by A.melas, A. nebulosus and A.
natalis such as competition (for food and/or space) with
native species, and predation of native species have
been reported. In the same way, A. natalis are adaptive
opportunistic and omnivores eaters, consuming
whatever is edible within their environment and has a
negative impact on native species, decreasing both the
abundance and diversity of species in an area (Hughes
and Herlihy, 2012).
Ameiurus spp. are normally considered detritivores but
recent studies suggest their diet include fish and fish
eggs (Boet, 1980). Therefore, this species might be
reducing the amount of available prey for native
predators. Due to the generalist and opportunistic
feeding habits of Ameiurus species, Leunda et al.
(2008) analyzed data from Spain and Portugal
indicating impacts of A. melas on a wide range of
potential prey species as well as impacts through
competition. In this study, black bullheads consumed
plant material, terrestrial prey and co-occurring fish
species (native or exotic), taking the most abundant and
available prey.
A. nataslis is partially responsible for the decline of the
Chiricahua leopard frog (Rana chiricahuensis) in
southeastern Arizona (Rosen et al., 1995; Fuller et al.,
1999).
Although A. nebulosus is not considered a quarantined
pest, several countries Switzerland (Wittenberg, 2005);
Poland (FAO, 1997); Chile (Welcomme, 1988))
reported adverse effects on native fish communities
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following its establishment.
Ruiz-Navarro et al. (2014) demonstrated that native fish
species play an important role in the diet of A. melas in
their invaded range (England), constituting ~30% of
food items ingested.
Out of the 37 fish species introduced to Spain, 31 are
freshwater species with the greatest potential for
ecological impact attributed to black bullhead Ameiurus
melas (Rafinesque, 1820) (42 % of all introductions
worldwide, n=21) followed by topmouth gudgeon
Pseudorasbora parva (Temminck and Schlegel, 1846)
(37% of all introductions worldwide, n=35) (Gozlan,
2010).
Due to the generalist and opportunistic feeding habits of
this species, Leunda et al. (2008) analysed data from
Spain and Portugal indicating impacts on a wide range
of potential prey species as well as impacts through
competition. In this study, black bullheads consumed
plant material, terrestrial prey and co-occurring fish
species (native or exotic), taking the most abundant and
available prey. Therefore, this species might be
reducing the amount of available prey for native
predators. Leunda et al (2008) study results suggest that
the black bullhead could be negatively affecting native
ichthyofauna in two ways. First, the results showed that
black bullheads are preying on native fish species such
as B. graellsii, P. miegii and G. lozanoi. Even if only
fish bony remains (e.g. scales, opercula, cleithra and
pharyngeal arches) were identified in black bullhead
stomachs, egg predation could not be excluded.
Probably, egg predation was not detected because of
rapid digestion. Secondly, this study showed that the
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diet composition of black bullhead is similar to the diet
described for some co-occurring Iberian native species.
Taking into account black bullhead’s voracity and
aggressive behaviour, the diet similarity might lead to
an unfavourable competition for the same food
resources, subsequently, displacing native fishes to
suboptimal food resources.
A. melas can reach populations as high as 227 kg/ha;
individuals have been found with large amounts of
vegetation in their stomachs (NatureServe 2006).
A. melas in small lakes, for example, on Lasqueti I. This
species and pumpkinseeds can extirpate a stickleback
population in 2 years (Cannings and Ptolemy 1998).
The catfish feeds on the eggs of the stickleback
(Backhouse 2000).
The Ameiurus species have similar nutrition habits,
eating benthic organisms such as molluscs, immature
insects, leeches, crustaceans, worms, algae, plant
material, fishes and fish eggs (Scott and Crossman,
1973), so we can affirm that the impact on the
environment is important, especially on the native
species.
Ameiurus melas
In the Slovak part of the middle Danube, invasive
species of fishes, especially two species of gobies
(Neogobius melanostomus and Neogobius kessleri),
topmouth gudgeon Pseudorasbora parva and black
bullhead Ameiurus melas, have become a serious
problem for native fish communities. Small benthic
native species, e.g. bullhead Cottus gobio, white‐finned
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gudgeon Gobio albipinnatus and stone loach B.
barbatula, virtually disappeared from the local fish
communities. The current list of invasive species of
fishes in Slovakia contains nine species (A. melas, C.
gibelio, pumpkinseed Lepomis gibbosus, monkey goby
Neogobius
fluviatilis, racer
goby Neogobius
gymnotrachelus, N. kessleri, N. melanostomus, Amur
sleeper Perccottus glenii and P. parva) (Novomeska
and Kovac, 2016).
CABI (2015a) remarks on the impact on Gila cypha and
Rana chiricahuensis populations. According to Marsh
and Douglas (1997), introduced A. melas feed on
endangered humpback chub, Gila cypha, in the Little
Colorado River (USA) and may exert a negative impact
on the population there
Also CABI (2015a) mentions impacts such as
competition (for food and/or space) with native species,
and predation of native species have been reported. This
species is normally considered a detritivore but recent
studies suggest its diet could include fish and fish eggs
(Boet, 1980). Minckley (1973) reported that A. melas is
considered a pest in Arizona as it forms large
populations which compete with more desirable fishes
for space and food. They are also voracious predators of
newly hatched gamefish (Whitmore, 1997). According
to Rosen et al. (1995), introduced predatory fishes,
including A. melas, are probably partially responsible
for the decline of the Chiricahua leopard frog (Rana
chiricahuensis) in south-eastern Arizona. Black
bullhead may also have an indirect effect by increasing
turbidity (Braig and Johnson, 2003), potentially
modifying the feeding efficiency of visual predators
(Reid et al., 1999; Utne-Palm, 2002). Black bullheads
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tend to be found in high local abundance, their
behaviour could therefore interfere with accompanying
species and negatively affect the behavior of native
predators and prey. “
The presence of A. melas in a lagoon in Zamora (Spain)
is considered the cause ot the decline of Pelodytes
punctatus and Discoglossus galganoi (MAGRAMA,
2016).
Black bullhead may therefore affect the native fauna in
three distinct ways. First, it may prey directly on some
species, therefore reducing the amount of available prey
for native predators. Second, black bullhead may have
an indirect effect by generating turbidity that can
modify the feeding efficiency of visual predators. Third,
due to their high local abundance, black bullhead
behaviour may interfere with accompanying species and
hence negatively affect the behavioural feeding phases
of native predators and the anti-predator behaviour of
native prey (Kreutzenberger et al., 2008).
These sorts of indirect effects on native freshwater
animals have been reported following the introduction
of non-native invasive species. For instance, the black
bullhead Ameiurus melas Rafinesque, an ictalurid
catfish native to North America, has become one of the
most successful exotic fish in European freshwater
ecosystems. A series of experiments has shown that the
presence of this invader reduces the predation success
of Esox lucius on minnows, not by actively competing
with pike for minnows, but simply by interfering with
the normal behaviour of pike. Infection levels by
parasites normally transmitted trophically from
minnows to pike may be reduced as a consequence.
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However, since pike switch to other food items, they
may be exposed to other parasites transmitted via these
different preys (Poulin et al., 2011).
Ameirus nebulosus
CABI (2015b) remarks on the impact on Gasterosteus
populations. Brown bullhead are scavengers as well as
predators, locating their prey in the substrate through
the use of their sensory barbels (Global Invasive
Species, 2006).
As an adaptation for prey capture within turbid waters,
the species uses oral barbels to sense food items. A.
nebulosus is a generalist omnivore, feeding mostly at
night and eating benthic organisms that occur frequently
within freshwaters: waste, molluscs, immature insects,
terrestrial insects, leeches, crustaceans, worms, algae,
plant material, fishes and fish eggs. Young (30-60 mm
total length) prefer chironomid larvae, ostracods,
amphipods, mayflies and other small aquatic
invertebrates
Ameiurus nebulosus introductions may lead to
competition for food or space and predation on small
fishes, invertebrates or other small food items. Of
particular concern is the potential for altered energetic
pathways within recipient ecosystems, given their
omnivorous diet and a body structure that precludes
predation from but all of the largest fishes.
As an adaptation for prey capture within turbid waters,
the species uses oral barbels to sense food items. A.
nebulosus is a generalist omnivore, feeding mostly at
night and eating benthic organisms that occur frequently
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
within freshwaters: waste, molluscs, immature insects,
terrestrial insects, leeches, crustaceans, worms, algae,
plant material, fishes and fish eggs (Scott and
Crossman, 1973). Young (30-60 mm total length) prefer
chironomid larvae, ostracods, amphipods, mayflies and
other small aquatic invertebrates (Scott and Crossman,
1973) (CABI, 2015b).
Feeds on a wide variety of items including snails,
freshwater crayfish, fish eggs, worms, insects (adults
and larvae), fish and algae. The main prey of adult
brown bull head in Lake Taupo, New Zealand are
freshwater crayfish (global Invasive Species, 2006).
Nonnative predators, including Brown Bullhead, have
been shown to reduce the abundanceand diversity of
native prey species in several Pacific Northwest rivers
Fuller and Neilson, 2017b).
A. natalis has a negative impact on native
decreasing both the abundance and diversity of
in an area. A. nataslis is partially responsible
decline of the Chiricahua leopard frog
chiricahuensis) in southeastern Arizona.
species
species
for the
(Rana
Since A. natalis have few predators, are able to survive
harsh environmental conditions and have a high
reproductive rate they are often the only species in
small, shallow lakes and can quickly overpopulate these
bodies of water (CABI, 2009).
Impact of Introduction: Introduced predatory fishes,
including the Yellow Bullhead, are likely at least
partially responsible for the decline of the Chiricahua
leopard frog Rana chiricahuensis in southeastern
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
Arizona, and have been shown to reduce the abundance
and diversity of native prey species in several Pacific
Northwest rivers (Fuller and Neilson, 2017c).
Ameiurus catus is apparently responsible for the
disappearance of Sacramento perch Archoplites
interruptus in Thurston Lake, California (Fuller and
Neilson, 2017d).
2.17. How important is the impact of the organism on
biodiversity likely to be in the future in Europe?
major
medium
The impact that occurs mostly on aquatic ecosystems is
very high, so the effect of invasive species such as
Ameiurus spp. is one factor more to add on the loss of
native biodiversity.
Negative impact such as competition (for food and/or
space) and predation of native species have been
reported to all analyzed species of Ameiurus.
(http://www.cabi.org/isc/).
Changes in water transparency and increase of turbidity
could affect all the ecosystems where Ameiurus spp. are
present.
2.18. How important is alteration of ecosystem function
(e.g. habitat change, nutrient cycling, trophic
interactions), including losses to ecosystem services,
caused by the organism currently in Europe (include any
past impact in your response)?
major
high
Of particular concern is the potential for altered
energetic pathways within recipient ecosystems, given
their omnivorous diet and a body structure that
precludes predation from but all of the largest fishes.
They are unpopular, because they form dense stunted
populations. Their adaptability and ferocious feeding
behaviour make them a grave threat to the native fish
and amphibian fauna. In places, they have built up huge
populations and replaced native fish species, probably
through competition for food (FOEN, 2006).
The loss of species, as well as the transformation of the
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habitat and modification of its natural conditions, such
as turbidity increased, supposes an important effect on
the function of ecosystems.
Impact on fishing as a cultural ecosystem service is
demonstrated: A fishery in North London succumbed to
this highly efficient invader, and the local angling club
had lost one of their best fisheries.
As included in the “Ecological risk assessment of nonindigenous species in Lake Balaton: a pilot study”
(http://eulakes-model.eu/media/files/ecological-riskassessment-of-non-indigenous-species-in-lakebalaton.pdf) the FISK assessments were undertaken
independently by the three co-authors. Each person
calculated the total FISK scores for each species.
Altogether nine species (Carassius gibelio; Perccottus
glenii; Anguilla anguilla; Lepomis gibbosus; Neogobius
fluviatilis; Gambusia holbrooki; Hypophthalmichtys
molitrix x nobilis; Ameiurus melas; Pseudorasbora
parva). 5 of the 9 examined fish species (55.6%) –
among of them Ameiurus melas- received FISK scores
≥19 (scores between 24 and 33), and thus could be
classified as species posing high risk to become
abundant in the Balaton catchment. For 6 species
(among of them Ameiurus melas), effect on the
Catchments seemed to be more significant, which could
mean the hardly quantifiable costs of ecosystem
services (Farber et al., 2002).
In France the results from Cucherousset et al. (2006)
study suggest that the invasion of A. melas has been
facilitated by the expansion of reed beds associated with
the diminution of agricultural pressure in recent
decades. This study represents an unusual example
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where human activities can have had an unexpected
effect by facilitating an invasive fish species.
Furthermore, A. melas abundance increases when
decreasing water depth (Brown et al. 1999) and the
production of a large amount of litter by the reed beds
might favour A. melas by limiting water depth.
This study examined the distribution and habitat
selection of the invasive black bullhead in the ditches
and surrounded temporary flooded habitats of an
artificial wetland in western France. A multiscale
approach was used to quantify patterns of A.melas
abundance in relation to physical habitat characteristics
in the ditch network. Young-of-the-year (YOY) and
adult A. melas largely dominated the local fish
assemblage but were highly variable among sites.
Although we found evidence for some fine-scale habitat
differences for YOY and adult individuals, the
abundance of A. melas was positively and consistently
related to the dominance of reed beds. Furthermore, A.
melas preferentially used reed beds as opposed to marsh
meadows during the flooding period. The results from
this study suggest that the invasion of A. melas has been
facilitated by the expansion of reed beds associated with
the diminution of agricultural pressure in recent
decades. This study represents an unusual example
where human activities can have had an unexpected
effect by facilitating an invasive fish species
(Cucherousset et al., 2006).
Ameiurus melas is related to the physic-chemical
dimension of water quality. Changes in water
transparency and increase of turbidity (Braig and
Johnson, 2003).
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Ameiurus species are responsible for the muddying of
the water in their search for food which may alter
ecosystems and stop other species to feed.
Ameiurus melas
Of the countries where it has been introduced in Europe
there may be impacts on habitat (direct or indirect),
potentially through increased turbidity related to
reduced macrophyte growth and reduced stability of
substrates (CABI, 2015).
Black bullhead may also have an indirect effect by
increasing turbidity (Braig and Johnson, 2003),
potentially modifying the feeding efficiency of visual
predators (Reid et al., 1999; Utne-Palm, 2002).
The greater impact of benthivorous fish on turbidity
within shallow systems may be an indirect one through
the destruction of macrophytes and subsequent
destabilization of unconsolidated substrates (Braig et al,
2003)
Ameiurus nebulosus
A. nebulosus may increase physical disturbance within
freshwaters due to their benthivorous feeding habits.
Although their barbels may aid in prey capture, foraging
aggressively within substrates may be necessary to
dislodge certain benthic prey items, which in-turn can
increase turbidity and lead to altered productivity and
nutrient cycling. Estimates regarding habitat impacts
following A. nebulosus introductions have not been
quantified (CABI, 2015).
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Ameiurus natalis
A. natalis are responsible for the muddying of the water
in their search for food which may alter ecosystems. It
has been suggested that this action makes it difficult for
visual predators such as centrarchids to find food.
2.19. How important is alteration of ecosystem function
(e.g. habitat change, nutrient cycling, trophic
interactions), including losses to ecosystem services,
caused by the organism likely to be in Europe in the
future?
major
high
Negative effects on aquatic ecosystems are intensifying
as they are suffering transformations by which worsens
its evolution in the future.
Both surface and bottom turbidity increased with adult
and juvenile black bullhead biomass (Braig and
Johnson, 2003). This has been demonstrated to have an
impact on the foraging success of native predators, such
as the pike Esox lucius (Kreutzenberger et al., 2008)
The Guadalquivir Estuary (Spain) is a highly productive
ecosystem that provides permanent habitats for
estuarine species as well as playing an important role as
breeding and adult-feeding grounds for marine species
(Baldó and Drake 2002; González-Gordillo and
Rodríguez 2003). Considering the current increase of
the A. melas population and its ability to feed
voraciously on a variety of prey from small aquatic
macroinvertebrates to fish (Leunda et al. 2008), further
impacts on estuarine ecosystem function and services
may occur but this requires further study (Garcia-deLomas et al., 2009).
As described in Vandekerkhove et al. (2013) there is
increasing evidence that IAS can adversely affect the
structure and functioning of aquatic ecosystems
(Kideys, 2002; Krisp and Maier, 2005; Klein and
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Verlaque, 2008). Alternatively, a change in structure
and functioning may also facilitate the introduction and
spread of alien species. A reduction in native species
richness – for example, caused by hydromorphological
changes – may affect the resilience of communities to
invasions (Dunstan and Johnson 2006), or
eutrophication may dramatically alter the food-web
structure in favour of non-native species. The latter is
true for many shallow lakes, where increased nutrient
levels have induced a shift from a top-down to a
bottom-up regulated food web structure, with reduced
control of invasive planktivorous and benthivorous fish
(Scheffer 1998). The effects of IAS and other pressures
are likely to reinforce each other, potentially resulting in
an invasional meltdown at the water body level
(Ricciardi 2001). At the regional scale, positive
feedback mechanisms might explain the observed
exponential increase in the numbers of alien species
(DAISIE 2009).
2.20. How important is decline in conservation status (e.g.
sites of nature conservation value, WFD classification)
caused by the organism currently in Europe?
major
high
Ameiurus melas is found in areas of high value for the
conservation of nature, so the loss of biodiversity
supposes a high decline in the conservation status of
these areas.
In Spain, this species is present in the National Park
Tablas
de
Daimiel
(http://www.castillalamancha.es/sites/default/files/docu
mentos/paginas/archivos/doc_1_es0000013_0.pdf). Its
reproduction is also confirmed in the Doñana Natural
Area.
In France the species is included in the list of Fish
species recorded on the Natura 2000 site of the Lower
Valley Doubs - Doubs and Clauge.
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2.21. How important is decline in conservation status (e.g.
sites of nature conservation value, WFD classification)
caused by the organism likely to be in the future in
Europe?
major
high
The loss of biodiversity and quality of the ecosystems
supposes a decline of the nature conservation value
which will be worse in the future in these
areas.
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Responses of the Index of Community Integrity quality
classes detailed in the table to different indicators of
water quality, physical habitat and biotic perturbations.
IBMWP (Alba-Tercedor et al., 2002) measures water
quality, QBR Munné et al. (2003) evaluates the
perturbation status of the riparian area. The responses to
the invasion status (measured as the proportion of
invasive species richness and abundance) are also
shown (Hermoso et al, 2010).
2.22. How important is it that genetic traits of the
organism could be carried to other species, modifying
their genetic nature and making their economic,
environmental or social effects more serious?
minimal
medium
There is no evidence of possibility of hybridisation with
native species.
I. punctatus (channel catfish) have been known to mate
with brown bullhead (Ameiurus nebulosus), yellow
bullhead (Ameiurus natalis), and black bullhead
(Ameiurus melas), resulting in a variety of hybrid
catfish (Florida Museum of Natural History. Online:
https://www.flmnh.ufl.edu/fish/discover/speciesprofiles/ictalurus-punctatus/)
Introgressive hybridization among A. nebulosus and A.
melas may difficult in its differentiation and,
furthermore, its control. Hybridization of A. natalis
with A. melas and A. nebulosus is rare.
Hybridization between brown bullhead and black
bullhead may occur where the species frequently cooccur. No other hybrids are known within North
America. A. nebulosus has been sequenced (CABI,
2015a, 2015b)
A. natalis has a diploid (2n) chromosome number of 62
and haploid/gametic number of 31. Hybridization with
A. melas and A. nebulosus is rare (CABI, 2009).
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2.23. How important is social, human health or other
harm (not directly included in economic and
environmental categories) caused by the organism within
its existing geographic range?
2.24. How important is the impact of the organism as
food, a host, a symbiont or a vector for other damaging
organisms (e.g. diseases)?
minimal
medium
No effects known (Wiesner et al. 2010).
Black bullheads can cause a painful sting if pectoral
spines puncture human flesh. Black bullheads contain
small amounts of venom at the ends of spine which can
cause pain for up to a week. ("A Boundary Waters
Compendium", 2004; Etnier and Starnes, 1993).
moderate
low
A painful wound can be inflicted by the sharp spines in
the fins of brown bullhead catfish if they are not
handled carefully. Toxins released by the fish contribute
to the pain of the wound (Global Invasive Species,
2006).
Transmission of pathogens could likely be a risk but,
currently, it is not enough documented.
Ameiurus melas host Flavobacterium columnare and
Edwardsiolla ictaluri. Diseases of Concern: Epizootic
ulcerative syndrome (Aphanomyces invadans) Susceptible Species of Aquatic Animals listed in
Schedule III of Canada’s Health of Animals
Regulations – shows high susceptibility to ECV
infection. Furthermore a significant mortality associated
with the typical signs of systemic viral infections was
observed in groups challenge with epizootic
haematopoietic necrosis virus (EHNV) (Gobbo et al.,
2010). Ranaviruses pose a potential threat to fishs and
amphibians. Has also been shown to host
Ancyrocephalus pricei in a UK population (Sheath et
al., 2015).
Epizootic haematopoietic necrosis was observed in 0+
and 1+ old black bullhead reared in polyculture with
carp. The disease induced mortality of 6 tons of this
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species over a one-month period (from mid-August to
mid-September), whereas no mortality in carp was
recorded at the time nor any sign of the disease in 1+
old carp reared in the same pond (Jeremic and
Radosavljevic, 2009).
A. natalis is known to be a host species for creepers
(Strophitus undulatus) and are also parasitized by
leeches (Hirudinea) (Gray et al., 2001). They are
known to host the larval stage (glochidia) of the
clam Anodonta grandis [Pyganodon grandis] (Hart and
Fuller, 1974).
A study of parasites of A. natalis in Texas by Mayberry
et al. (2000) found the following:
Cestoda: Proteocephalidae, Proteocephalus
ambloplitis; Trematoda: Alloglossidium
kenti, Cleidodiscus pricei, Phyllodistomum
caudatum, Posthodiplostomum minimum, Gyrodactylus;
Nemata: Spinectus carolini [Spinitectus
carolini], Spinectus microcantus [Spinitectus
microcanthus], Spyroxis contorta.
Scott and Crossman (1973) describe the following
parasites known from within the species, which have
the potential to infect recipient fish communities
following A. nebulosus introductions: Protozoa,
Trematoda, Cestoda, Nematoda, Acanthocephala,
leeches,
Mollusca,
and
Crustacea.
(http://www.cabi.org/isc/datasheet/94468).
In Italy, the introduction of the exotic cestode
Corallobothrium parafimbriatum Befus et Freeman,
1973 with A. melas was recorded. The further spreading
of the cestode with its fish host to other countries was
not recorded. Acanthocephalus anguillae, adopted by
black bullhead, is the common parasite of native fishes
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(about 40 species) in Slovakia (Košuthová et al., 2009).
2.25. How important might other impacts not already
covered by previous questions be resulting from
introduction of the organism? (specify in the comment
box)
NA
2.26. How important are the expected impacts of the
organism despite any natural control by other organisms,
such as predators, parasites or pathogens that may already
be present in Europe?
major
medium
It is not well know how predators, parasites or
pathogens could affect the species. At least in Spain the
only possible fish predators will be also exotic. Native
species are usually smaller (70% of then endemic) and
with small mouths which make them bad competitors.
Although A. nebulosus are predated upon by larger
fishes, the likelihood of long-distance dispersal
resulting from this vector is low. Most piscivorous
fishes are unable to utilize A. nebulosus for food due to
their sharp, strong dorsal and pectoral spines that may
lock into an erect position when predated upon (CABI,
2015b).
Ameiurus melas have large sharp spines on both their
dorsal and pectoral fins; when attacked they straighten
them making them difficult to swallow and as such very
few predators are able to consume them. This species
also produces a mild poison that runs down the spines
and into the wound. These spines combined with the
species' nocturnal feeding regime make black bullheads
an uncommon prey item for other fish species.
Smallmouth bass (Micropterus dolomieu), largemouth
bass (Micropterus salmoides), herons as well as some
turtle species occasionally consume the young and
small adults, with their main predator being humans.
(CABI, 2015a)
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Ameiurus nebulosus. By virtue of its strong pectoral and
dorsal spines, the adult A. nebulosus is well protected
from predation by all but the largest fish predators in
their native range in Canada. Although present in
juveniles, the spines are less robust making juveniles
more susceptible to predation by fishes with a wider
range in size. Within its native range, predators include
members of the pike family (Esox spp.) and pike
perches (Sander spp.). Where introduced on the Gulf
Islands of British Columbia in Canada, there are no
other piscivorous fishes present and, hence, no native
predators to introduced A. nebulosus (CABI, 2015b).
Ameiurus natalis
Several natural enemies of A. natalis have been reported
in its native range; however, by virtue of their strong
pectoral and dorsal spines, adults are well protected
from predation by all but the largest fish predators
Members of the pike family (Esox species), walleye
(Sander vitreus), large wading birds and some turtles
may feed on adults.
Juvenile spines are less robust making them more
susceptible to predation by fishes with a wider range in
size. Within its native range, predators of juveniles
include Micropterus salmoides, M. dolomieu, Sander
canadensis, species of Ambloplites and Pomoxis
including Pomoxis nigromaculatus and other catfish as
well as aquatic invertebrates, leeches and crayfish. The
eggs and small fry are predated by Lepomis
macrochirus and other species of Lepomis (CABI,
2009).
2.27. Indicate any parts of Europe where economic,
[In all rivers,
medium
Negative impacts could occur in all the distribution area
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environmental and social impacts are particularly likely to
occur (provide as much detail as possible).
reservoirs,
dams, lakes,
lagoons and
ponds]
where it is established.
Particularly National Parks, areas of high value for the
conservation of nature are more susceptible to suffer
high economic, environmental and social negative
impacts.
In Spain, the National Park Tablas de Daimiel
(http://www.castillalamancha.es/sites/default/files/docu
mentos/paginas/archivos/doc_1_es0000013_0.pdf). and
the Doñana Natural Area are two important
conservation areas that suffers because of the
reproduction of Ameiurus melas in their waters
In France the species is included in the list of Fish
species recorded on the Natura 2000 site of the Lower
Valley Doubs - Doubs and Clauge.
Ameiurus melas
There is potential for the black bullhead to cause a
negative social impact as it can be a 'nuisance' species
taking lines/bait intended for other species, because of
this anglers not targeting this species might move on to
black bullhead free waters (CABI, 2015a).
Ameiurus nebulosus populations may hinder local
native sport fisheries by out-competing target fishes,
resulting in reduced angling opportunities and their
social impacts. Alternatively, introductions may be
encouraged locally if A. nebulosus are favoured for
sport. Introduction into previously fishless waters may
provide new or valued angling opportunities. Current
estimates of social impacts resulting from introductions
have not been documented (CABI, 2015b).
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RISK SUMMARIES
Summarise Entry
RESPONSE
Moderately
CONFIDENCE
high
Summarise Establishment
very likely
high
Summarise Spread
moderately
medium
COMMENT
At least four of the total of seven species of Ameiurus
genus are already present in Europe, (24 of the total of
28 European countries have recorded at least one
Ameiurus sp). In the meantime the interest of this
species for fishing has been reduced lately, and some
countries have forbidden new entries of A. melas and A.
neboulosus (France, Poland, etc.).
At least one Ameiurus sp. (A. melas) is established in
France, Germany, Austria, Italy, Portugal, Spain, the
Netherlands, Belgium, Czech Republic, Croatia,
Romania, Finland, Hungary, Slovakia, Slovenia,
Bulgaria, Greece, Croatia, Ireland, Romania, Poland,
Sweden, Denmark, Estonia and the United Kingdom. A.
nebulosus has been cited as established in many
countries, although it seems to be A. melas in most
cases. A. melas and A. nebulosus would probably adapt
easily to the climatic conditions in Malta and Cyprus
and possible in Lithuania and Latvia.
This demersal species inhabits low-flowing habitats
(limnophilic) with soft substrata in all riverine and
lacustrine environments, including artificial ones such
as ponds and reservoirs.
The expansion depends on ecological conditions of
river basins in which it is introduced, but if it finds
suitable conditions, it can be easy for these successful
invaders to spread. A reduction in native species
richness – for example, caused by hydromorphological
changes or anthropogenic influences – may affect the
resilience of communities to invasions (Dunstan and
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
Johnson, 2006), or eutrophication may dramatically
alter the food-web structure in favour of non-native
species.
This means that Ameiurus spp. could spread easily to
other ecosystems.
Flexible life-history traits and wide environmental
tolerances facilitate Ameiurus spp. establishment and
dispersal.
Summarise Impact
major
medium
Ameiurus spp. is generalist, foraging on the most
abundant and available prey. The impact is because of
the competition, due to the coincidences with the preys
used by some native species, direct predation of native
species and habitat degradation.
Impacts in water quality, such as increased turbidity,
have also been demonstrated.
Conclusion of the risk assessment
major
medium
The release and translocation of specimens by
fishermen and pet-owners and the easy adaptability to
the natural conditions in the lakes and rivers from
Europe, makes possible its continuous expansion
transforming aquatic ecosystems and causing the
disappearance of native species, mainly fish.
Aquatic habitats are one of the habitats more threatened
by invasive alien species (IAS). At present IAS are one
of the most important direct drivers of biodiversity loss
throughout the world and constitute the greatest threat
to fragile ecosystems such as small isolated water
bodies.
ADDITIONAL QUESTIONS - CLIMATE CHANGE
3.1. What aspects of climate change, if any, are most
[Temperature
medium
The effects of climate change in the progressive
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
likely to affect the risk assessment for this organism?
warming of water, even in temporary drying up of
rivers, during which this species is able to stay buried in
the mud, would favour its population increase, which
would be a major impact on native species.
Species composition, diversity, global abundance and
size structure of fish communities exhibited important
trends related to water warming in large rivers
(http://www.firf.fr/team/martin/1fichiers/1pdf/Daufresn
eGCB2007.pdf).
Cucherousset et al. (2007) studied fish emigration
patterns from four temporary wetlands exposed to
drought from May to August 2004 in the Brière Marsh
(France). Emigration timing was highly correlated with
published physiological tolerance levels for these
species, demonstrating a tight linkage between water
quality and emigration patterns. Two non-native species
(A. melas and G. holbrooki) showed the latest
emigration from the temporary habitats, reflecting a
high level of tolerance to drought conditions that may
contribute to their success as wetland invaders
(Cucherousset et al, 2007).
; rain]
3.2. What is the likely timeframe for such changes?
40 years
low
3.3. What aspects of the risk assessment are most likely to
change as a result of climate change?
[Increase
medium
suitability of
the habitat for
The greater hydrological variability predicted to
accompany the warmer climatic conditions is expected
to increase fish dispersal, so wider establishment of
non-native fishes is likely to enhance the risks of
adverse consequences for native species and ecosystems
(Coop et al, 2004). However, existing evidence for
adverse impacts remains equivocal or lacking for many
nonnative fishes
Aquatic environments are particularly affected by
climate change.
The water temperature could also explain the change in
habitat use and searching behaviour by bullheads. In the
wild, bullheads and crappies would compensate for the
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EU NON-NATIVE SPECIES RISK ANALYSIS – RISK ASSESSMENT TEMPLATE V1.0
the species]
increased water temperature by finding areas that
contain cool water temperatures, allowing their body
temperature to cool as a result. (Walberg, 2011). This
could result in a natural spread in colder waters such as
Latvia´s and Lithuania´s ones, where Ameiurus spp
seem not to be recorded yet.
Additionally, where A. melas is present in more
temperate climates (UK for example), increased water
temperatures as a result of climate change could extend
the period for successful spawning and increase
foraging efficacy (Environment Agency- UK,
unpublished data).
ADDITIONAL QUESTIONS - RESEARCH
4.1. If there is any research that would significantly
strengthen confidence in the risk assessment please
summarise this here.
[The impact to
native fauna
should be
further
investigated]
medium
Confidence in the risk assessment is high for
establishment, spread and damage in aquatic
ecosystems. Data on the possible impacts on native
species, principally on endemic fishes, are needed.
Further studies are required to assess these impacts. It
would be very important to increase the management
actions to protect them.
Research into the efficacy of bio-control and biomanipulation of A. melas populations should be
investigated (cf. Davies and Britton, 2015), to provide
additional control measures to those already available
(See Comment 1.21).
Further investigation is needed to assess Ameiurus
population trends and impacts, such as decline of
reservoir water quality and food web structure
alteration.
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Further cost data are also needed.
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