Download The rapid colonization by Crangon crangon (Linnaeus, 1758

THE RAPID COLONIZATION BY CRANGON CRANGON (LINNAEUS, 1758)
(EUCARIDA, CARIDEA, CRANGONIDAE) OF ICELANDIC
COASTAL WATERS
BY
BJÖRN GUNNARSSON1,3 ), ÞÓR H. ÁSGEIRSSON1,4 ) and AGNAR INGÓLFSSON2,5 )
1 ) Marine Research Institute, P.O. Box 1390, Skúlagata 4, IS-121 Reykjavík, Iceland
2 ) Institute of Biology, University of Iceland, Sturlugata 7, IS-101 Reykjavík, Iceland
ABSTRACT
The European brown shrimp, Crangon crangon (L., 1758) has colonized the intertidal zones of
Iceland and spread rapidly to many coastal areas. The first confirmed record dates from 2003, and
by 2006 the species had colonized the west and south coasts, while not being recorded on the north
and east coasts. Densities as high as 6700 animals 100 m−2 were measured. The absence of the
brown shrimp from Iceland until recently is interesting in the light of its occurrence in Arctic waters,
especially off northern Norway and Russia. It seems most likely that it was brought to Iceland by
ballast water. The present records substantially extend the known geographical range of this species.
RÉSUMÉ
La crevette grise européenne Crangon crangon (L., 1758) a colonisé les zones intertidales
d’Islande et s’est étendue rapidement à de nombreuses zones côtières. Les premières données fiables
datent de 2003; Depuis 2006, l’espèce a colonisé les côtes ouest et sud alors qu’elle est encore
absente sur les côtes nord et est. Des densités de 6700 animaux 100 m−2 ont été mesurées. L’absence
de la crevette grise en Irlande jusqu’en des temps récents est intéressante à la lumière de sa présence
dans les eaux arctiques, en particulier au large des côtes nord de la Norvège et de la Russie. Il est
probable qu’elle a été apportée en Islande par les eaux de ballast. Les données présentes étendent
substantiellement la zone de distribution géographique connue de cette espèce.
INTRODUCTION
The European brown shrimp, Crangon crangon (L., 1758) (Eucarida, Caridea,
Crangonidae) is commonly found in large numbers in the eulittoral and sublittoral
3 ) e-mail: [email protected]
4 ) e-mail: [email protected]
5 ) e-mail: [email protected]
© Koninklijke Brill NV, Leiden, 2007
Also available online: www.brill.nl/cr
Crustaceana 80 (6): 747-753
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BJÖRN GUNNARSSON ET AL.
soft-bottom habitats of temperate waters of the North-East Atlantic (Henderson
& Holmes, 1987; Hostens, 2000). Its distribution extends from the White Sea
and northern Norway, as well as the Baltic in the north, to the Atlantic coast of
Morocco, including the Mediterranean and the Black Sea in the south (Tiews,
1970), but it has hitherto not been reported in Icelandic waters. It plays a
trophic key role in the coastal marine food web, facilitating the transfer of
energy between the benthic and the pelagic habitat (Pihl & Rosenberg, 1982,
1984; Evans, 1984). The brown shrimp is harvested commercially in northern
European waters with 32.000 tonnes landed in 2003 (ICES, 2005). Most animals
inhabiting the rocky shores of Norway are also found in Iceland (Ingólfsson,
2006), which makes the previous absence of C. crangon from Icelandic waters
curious.
Here, we describe the recent colonization of C. crangon in Icelandic waters from
its first record in 2003. We present its known distribution until 2006 and discuss
the future of the species in Iceland.
METHODS
The coast of Iceland is about 6500 km long (excluding tidal flats), the greatest
portion consisting of moderately steep rocky shores. Exposed, apparently barren,
sandy shores are estimated to be about 560 km in length (Ingólfsson, 2006).
Ingólfsson (2006) further estimates that about 40% (about 175 km2 ) of the
intertidal in Iceland comprises relatively protected tidal flats, presumably suitable
habitats for Crangon crangon.
Two distinct sampling methods have yielded brown shrimps in Icelandic waters.
In 2003, 2005, and 2006 the shrimps were collected with a 1 m wide beam trawl,
whereas tidal flats (Blikastadarleira) were sampled by sieving sediment samples.
In the beam trawl studies, the target was juvenile plaice (Pleuronectes platessa
L., 1758). The 5.5 m long trawl is equipped with a tickler-chain and 8 mm mesh
size in the main body and 5.5 mm in the cod end. The towing speed was kept
as constant as possible during sampling, at an average of 35 m min−1 . The gear
was pulled parallel to the beach by two persons for approximately three minutes.
A GPS equipment recorded the distance covered and the surface area sampled was
approximately 100 m2 . The average depth at each station ranged from 0.5 to 1 m.
On each occasion, two or three replicate hauls were made. Samples were stored
in plastic buckets and sorted within a few hours in the laboratory. The brown
shrimps were identified to species, counted, and the total length from the tip of
the rostrum to the tip of the telson was measured to the nearest millimetre. The
identification was confirmed by Marit E. Christiansen, Natural History Museum,
CRANGON CRANGON (L.) COLONIZATION OF ICELANDIC COASTS
749
Fig. 1. Sampling sites in July 2006. Sites where the brown shrimp, Crangon crangon (L., 1758) was
found are marked with black dots, whereas grey dots indicate sites without brown shrimp. The arrow
indicates the tidal flat, Blikastaðir, which has been sampled since 1971. The numbers refer to the list
of sites given in table I and in the text.
Oslo, and by Henk van der Veer, Netherlands Institute for Sea Research, Texel.
When converting the catch to numbers per m2 , no correction was made for gear
efficiency.
The most complete trawl survey was done in July 2006, when virtually all the
main coastal areas of Iceland were covered (fig. 1). The sampling sites (stations)
were selected based on shore type (sandy shores), accessibility by a 4-wheel drive
vehicle, and the experience from the sampling programme in 2005. A total of 30
stations was sampled (stations no. 1-30, fig. 1) during a 12-day period in July. The
sampling took place during two hours around neap tide.
The Blikastaðir tidal flats, southwestern Iceland (fig.1), have been monitored
regularly since 1971, on altogether 20 occasions (Ingólfsson, 2006). These flats are
low-lying and only accessible during low tides. For the past 10 years the flats were
sampled in 1997, 1998, 2001, 2004, 2005, and 2006. On each occasion, sediment
down to a depth of 5 cm was collected from 20 × 20 or 50 × 50 cm quadrats.
The quadrats were either placed randomly or along transects. The samples were
washed through sieves with meshes of 1, 2, and 8 mm. The animals retained were
identified and measured in the laboratory.
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BJÖRN GUNNARSSON ET AL.
RESULTS
The first confirmed record of Crangon crangon from Icelandic waters dates
from 2003, from Álftanes (station 2, fig. 1) (Jónbjörn Pálsson, Marine Research
Institute, pers. comm.). The shrimps were, however, first identified to species in
2005. At Blikastaðir tidal flats (fig. 1) shrimps appeared for the first time in October
2004, having never been recorded there before. The average density (using 1 or 2
mm sieves) in 2004 was estimated at 6700 animals 100 m−2 (SD = 9100). The
shrimps were also present at this location in August 2005 (average density 500
animals 100 m−2 , SD = 480) and August 2006 (average density 1300 animals
100 m−2 , SD = 680). Further presence of C. crangon on the Icelandic coasts was
confirmed in 2005 when the shrimp was caught at several localities during a survey
of juvenile plaice. That year the shrimp was found in large numbers (402 animals
100 m−2 ) at a site in the northern Bay of Faxaflói (approximately 30 km east of
station 4, fig. 1). A similar survey of juvenile plaice took place there in 1999, but
no Crangon was found as stated explicitly by Hjörleifsson & Pálsson (2001). The
survey in 2006 gives a near complete indication of the distribution of C. crangon
along the Icelandic coast at that time. C. crangon was found on the entire west and
south coasts with densities up to 152.5 animals 100 m−2 (station no. 30, table I).
The individuals found on the south coast were smaller than those found on the west
coast, ranging in size from (average) 18.4 to 26 mm in the south and 34.5 (station
7) to 77.6 mm (station 1) on the west coast. Ovigerous females were common. No
animals were found on the north and east coasts (stations 8-25, fig. 1).
DISCUSSION
The present study strongly suggests that the brown shrimp, Crangon crangon
has colonized the intertidal areas of Iceland sometime between 2001 (when the
animals were absent at Blikastaðir tidal flats) and 2003 (when first found at
Álftanes). Since 2003, C. crangon has spread quickly along the west and south
coasts. In 2005, only two small animals (<15 mm) were found at station 6 and no
animals at all were found at station 7 (fig. 1). In 2006, several animals, ranging in
size from 25 to 78 mm, were found at station 6 and a few animals were found at
station 7. These findings may indicate a northward extension along the west coast.
The absence of large animals (>50 mm) in samples taken along the south coast in
2006 may also suggest a recent colonization.
The great difference in density between the monitoring at Blikastaðir tidal flats
and the plaice survey (500-6700 animals 100 m−2 and 1-153 specimens 100 m−2 ,
respectively) can be explained by the type of sampling device used. The fine sieve
used in the monitoring deals with small (postlarval) stages of C. crangon only.
CRANGON CRANGON (L.) COLONIZATION OF ICELANDIC COASTS
751
TABLE I
Sites in Iceland where the brown shrimp, Crangon crangon (L., 1758) was found in July 2006, along
with density and mean length. See fig. 1 for location of the stations. Samples from 2003 and 2005
are indicated in footnotes
Region name
Station
no.
Density
(no. 100 m−2 )
Mean length
(mm)
Span
(mm)
Sandgerði
Álftanes
Ólafsvík
Búðir
Akranes
Brjánslækur
Patreksfjörður
Papós
Hornafjörður
Dyrhólaós
Ölfusárós
1
2+ *
3*
4*
5
6*
7
26
27
29
30
11.3
30.3
10.0
33.0
72.6
9.3
1.0
2.0
2.5
1.5
152.5
54.3
45.5
36.8
43.1
38.9
36.7
34.5
26.0
18.4
22.3
18.6
36-63
30-60
25-56
29-72
27-60
25-78
32-34
16-45
16-23
20-24
10-33
+ Also found in survey 2003.
∗ Also found in survey 2005.
The shrimp up to a size of 25 mm stays permanently on the tidal flats (Janssen
& Kuipers, 1980), hiding in the wet sediment at low tide. The beam trawl, on
the other hand, probably only catches part of the smaller shrimps buried in the
sand/mud. Density comparisons between the two gears should, therefore, be made
with caution. The shrimp densities obtained by sieving the sediment on tidal flats
in Iceland appear comparable to those in the Gullmarfjord in Sweden, in the
Skagerrak, and on the French eastern coast of the Channel (Wennhage & Pihl,
2001; Amara & Paul, 2002).
All records of C. crangon reported here are from the warm Atlantic waters on
the south and west coasts. The species reaches far into the Arctic in northern
Norway and Russia (Tiews, 1970) and it is therefore unlikely that any recent
increase in temperature is a factor in the colonization of the species. Also,
all macrofaunal animals in the intertidal on the east coast of Iceland, where
temperatures are the lowest, co-occur in extreme northern Norway (Ingólfsson,
2006).
It is well known that many marine animals, especially planktonic ones or species
with planktonic larvae, are carried around in the ballast water of ships, thus being
accidentally introduced in to new areas (e.g., Carlton, 2003). Decapod shrimps
would therefore seem to be well suited for dispersal in ballast water. Nevertheless,
accidental introductions of shrimp to foreign waters appear scarce (e.g., Emmet et
al., 2003), and we are not aware of any evidence that C. crangon has been carried
accidentally to new areas. As the planktonic larval stages are much too short lived,
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BJÖRN GUNNARSSON ET AL.
about 5 weeks (Criales & Anger, 1986), for the larvae to be carried by currents
from Scotland or Norway to Iceland (see discussion in Ingólfsson, 2006), it is
difficult to explain the present colonization except by ballast water introduction.
We predict that in the next few years C. crangon will be found widely in northern
and eastern Iceland, where the species currently (2006) still appears to be absent.
ACKNOWLEDGEMENTS
We wish to express our gratitude to Tryggvi Sveinsson at the Marine Research
Institute, Reykjavik, and to students of Marine Ecology at the University of Iceland
for assistance during sampling in the field. We are also grateful to Jonbjörn Pálsson
for samples he provided and to Astthor Gislason, Olafur Astthorsson, and Kristján
Lilliendal for critical reading of the manuscript.
REFERENCES
A MARA , R. & C. PAUL, 2002. Seasonal patterns in the fish and epibenthic crustaceans community
of an intertidal zone with particular reference to the population dynamics of plaice and brown
shrimp. Estuar. coast. Shelf Sci., 56: 807-818.
C ARLTON , J. T., 2003. Community assembly and historical biogeography in the North Atlantic
Ocean: the potential role of human-mediated vectors. Hydrobiologia, 503: 1-8.
C RIALES , M. M. & K. A NGER, 1986. Experimental studies on the larval development of the
shrimps Crangon crangon and C. allmani. Helgoländer Meeresunters., 34: 241-265.
E MMET, R. L., S. A. H INTON , D. J. L OGAN & G. T. M AC C ABE, 2003. Introduction of freshwater
shrimp to western North America. Biol. Invas., 4: 447-450.
E VANS , S., 1984. Energy budgets and predation impact of dominant epibenthic carnivores on a
shallow soft bottom community at the Swedish west coast. Estuar. coast. Shelf Sci., 18: 651672.
H ENDERSON , P. A. & R. H. A. H OLMES, 1987. On the population biology of the common shrimp
Crangon crangon (L.) (Crustacea: Caridea) in the Severn Estuary and Bristol Channel. Journ.
mar. biol. Assoc. U.K., 67: 825-847.
H JÖRLEIFSSON , E. & J. PÁLSSON, 2001. Settlement, growth and mortality of 0-group plaice
(Pleuronectes platessa) in Icelandic waters. Journ. Sea Res., 45: 321-324.
H OSTENS , K., 2000. Spatial pattern and seasonality in epibenthic communities of the Westerschelde
(Southern Bight of the North Sea). Journ. mar. biol. Assoc. U.K., 80: 27-36.
ICES, 2005. Report of the Working Group on Crangon Fisheries and Life History. C.M.2005/G:01.
I NGÓLFSSON , A., 2006. The intertidal seashore of Iceland and its animal communities. Zool.
Iceland, 1(7): 1-85.
JANSSEN , G. M. & B. R. K UIPERS, 1980. On tidal migration in the shrimp Crangon crangon.
Netherlands Journ. Sea. Res., 14: 339-348.
P IHL , L. & R. ROSENBERG, 1982. Production, abundance and biomass of mobile epibenthic marine
fauna in shallow waters, western Sweden; Journ. exp. mar. Biol. Ecol., 57: 273-301.
— —, 1984. Food selection and consumption of the shrimp Crangon crangon in some shallow
marine areas in western Sweden. Mar. Ecol. Progr. Ser., 15: 159-168.
T IEWS , K., 1970. Synopsis of biological data on the common shrimp Crangon crangon (Linnaeus,
1758). FAO Fish. Rep., 4: 1167-1224.
CRANGON CRANGON (L.) COLONIZATION OF ICELANDIC COASTS
753
W ENNHAGE , H. & L. P IHL, 2001. Settlement patterns of newly settled plaice (Pleuronectes
platessa) in a non-tidal Swedish fjord in relation to larval supply and benthic predators. Mar.
Biol., Berlin, 139: 877-889.
First received 27 December 2006.
Final version accepted 26 January 2007.