Download Long-term shifts in abundance and distribution of a

Global Ecology and Biogeography, (Global Ecol. Biogeogr.) (2011) 20, 58–72
RESEARCH
PA P E R
Long-term shifts in abundance and
distribution of a temperate fish fauna:
a response to climate change and
fishing practices
geb_575
58..72
Peter R. Last1,2*, William T. White1,2, Daniel C. Gledhill1,2,
Alistair J. Hobday1,2, Rebecca Brown3, Graham J. Edgar3 and Gretta Pecl3
1
Climate Adaptation Flagship, CSIRO Marine
and Atmospheric Research, GPO Box 1538,
Hobart TAS 7001, Australia, 2Wealth from
Oceans Flagship, CSIRO Marine and
Atmospheric Research, GPO Box 1538, Hobart
TAS 7001, Australia, 3Tasmanian Aquaculture
and Fisheries Institute, Private Bag 49, Hobart
TAS 7001, Australia
A B S T R AC T
Aim South-eastern Australia is a climate change hotspot with well-documented
recent changes in its physical marine environment. The impact on and temporal
responses of the biota to change are less well understood, but appear to be due to
influences of climate, as well as the non-climate related past and continuing human
impacts. We attempt to resolve the agents of change by examining major temporal
and distributional shifts in the fish fauna and making a tentative attribution of
causal factors.
Location Temperate seas of south-eastern Australia.
Methods Mixed data sources synthesized from published accounts, scientific
surveys, spearfishing and angling competitions, commercial catches and underwater photographic records, from the ‘late 1800s’ to the ‘present’, were examined to
determine shifts in coastal fish distributions.
Results Forty-five species, representing 27 families (about 30% of the inshore fish
families occurring in the region), exhibited major distributional shifts thought to
be climate related. These are distributed across the following categories: species
previously rare or unlisted (12), with expanded ranges (23) and/or abundance
increases (30), expanded populations in south-eastern Tasmania (16) and extralimital vagrants (4). Another 9 species, representing 7 families, experienced longerterm changes (since the 1800s) probably due to anthropogenic factors, such as
habitat alteration and fishing pressure: species now extinct locally (3), recovering
(3), threatened (2) or with remnant populations (1). One species is a temporary
resident periodically recruited from New Zealand. Of fishes exhibiting an obvious
poleward movement, most are reef dwellers from three Australian biogeographic
categories: widespread southern, western warm temperate (Flindersian) or eastern
warm temperate (Peronian) species.
Main conclusions Some of the region’s largest predatory reef fishes have become
extinct in Tasmanian seas since the ‘late 1800s’, most likely as a result of poor fishing
practices. In more recent times, there have been major changes in the distribution
patterns of Tasmanian fishes that correspond to dramatic warming observed in the
local marine environment.
*Correspondence: Peter Last, CSIRO Marine
and Atmospheric Research, GPO Box 1538,
Hobart TAS 7001, Australia.
E-mail: [email protected]
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Keywords
Climate change, fishing, south-eastern Australia, spatial shift, Tasmania,
temperate fishes, temporal shift.
DOI: 10.1111/j.1466-8238.2010.00575.x
© 2010 Blackwell Publishing Ltd www.blackwellpublishing.com/geb
Long-term shifts in a temperate fish fauna
INTR O D U C TI O N
Changes in faunal assemblages over time have been recorded in
many marine communities and are often linked to anthropogenic impacts, such as fishing (e.g. Jackson et al., 2001), pollution (e.g. Schiel et al., 2004), invasive species (e.g. Currie &
Parry, 1999) and climate change (e.g. Holbrook et al., 1997;
Sagarin et al., 1999; Hiddink & Hofstede, 2008). Significant
changes in aquatic communities have been strongly associated
with global warming, suggesting that these ecosystems are
extremely vulnerable to climate change (Richardson &
Poloczanska, 2008). The effect of climate change on temperate
inshore marine communities, specifically in rocky intertidal
zones, has been demonstrated in a number of studies (e.g.
Sagarin et al., 1999; Helmuth et al., 2006), with studies of the
effects of climate on temperate fish communities in the North
Atlantic (e.g. Perry et al., 2005; Hiddink & Hofstede, 2008) and
eastern (Holbrook et al., 1997) and south-west Pacific (StuartSmith et al., 2009). The Antipodean region is recognized as a
‘hotspot’ for ocean warming (Ridgway, 2007). Since 1944, the
East Australian Current (EAC) has extended poleward down the
coast of Tasmania by approximately 350 km and the sea surface
temperature has warmed at an average rate of 2.28°C per
century (Ridgway, 2007; see also Fig. 1). Thus, biological
responses to climate change in the region are expected to have
already begun (Hobday et al., 2007; Ling et al., 2009).
The relatively species rich, cool temperate coastal ichthyofauna of Tasmania is ideal for investigating temporal and spatial
shifts in species composition in this hotspot. The region is wellseparated geographically from mainland Australia, but the
respective faunas are loosely interconnected through the Bass
Strait by a series of island groups that potentially form ‘stepping
stones’ for the southward dispersal of adult fishes from northern
bioregions. Although complex, the biogeography of southeastern Australia, which has been the subject of detailed investigation for the purpose of regional marine planning (IMCRA,
1996), is now reasonably well understood. The Tasmanian fish
Figure 1 The average annual sea surface temperature anomaly
from the long-term average calculated from the HadlSST dataset
(monthly, 1 °C; Rayner et al., (2003); http://hadobs.metoffice.com/
hadisst/) for the area illustrated in the inset map [40–44° S,
147–151° E] for each year (dotted line) and for each decade (open
bars) over the period 1880–2009.
fauna has been described in a series of checklists and guides
dating back to the late 1800s and early 1900s (e.g. Lord & Scott,
1924). In the ‘1980s’, these fishes were surveyed extensively and
good intra-regional information was obtained on the distributions of most species (e.g. Last et al., 1983). However, since the
mid-1990s many unusual records and sightings have been
reported, including coastal species not previously reported from
the region, poleward extensions of ‘1980s’ ranges, and increased
local abundances in southern parts of Tasmania.
Stuart-Smith et al. (2009) concluded that Tasmanian subtidal
reef communities have remained stable over the past decade
despite evidence of localized ocean warming (Ridgway, 2007).
Nevertheless, they detected some species-level responses considered to be symptomatic of ocean warming, including southward
range extensions of some fishes. They suggested that major
changes in faunal structure probably occurred in the decade
prior to commencement of their study; for example, forests of
giant kelp (Macrocystis pyrifera) initially declined in the ‘1980s’
(Edyvane, 2003). Hence, by examining shifts over a longer time
frame we should be able to gain better insights into the extent of
change. Stuart-Smith et al. (2009) also observed that less abundant species often exhibited greater shifts than the dominant
elements of the fauna, presenting challenges when monitoring
climate impacts.
Since 2006, when the senior author made an oral presentation
describing range changes in south-eastern Australian fishes, patterns of distributional shift in the fauna have become widely
accepted (e.g. Hobday et al., 2007) but have not been rigorously
described. In addition, global warming may not be the only
driver of change in the region – changes in the fauna may have
occurred due to exploitation. Resolving these agents of change is
important because not all distributional shifts are necessarily
climate related. Recolonization may occur in response to
changes in fishing pressure, allowing a return of fishes from
populations in less heavily exploited regions. Attribution of
change is important for improving coastal management strategies, as well as recording and predicting the impacts of climate
change.
The following hypotheses are evaluated using a combination
of historical and present-day data sources: (1) the coastal ichthyofauna has experienced significant temporal losses of some
elements since the ‘late 1800s’ evident from local extirpation or
major reduction in population size and distribution of some
species, and (2) the ichthyofauna has exhibited a marked change
in composition since the ‘1980s’, with these differences represented by range extensions of warm-temperate provincial
elements from the north. Herein, we define the coastal
ichthyofauna as an assemblage of fishes (about 300 species)
that have been recorded from the coastal zone of Tasmania.
METHO DS
Data sources
The Tasmanian coastline is situated south of latitude 39°12′ S in
the Australian Exclusive Economic Zone (EEZ) and includes the
Global Ecology and Biogeography, 20, 58–72, © 2010 Blackwell Publishing Ltd
59
P. R. Last et al.
Figure 2 The Maugean region of
south-eastern Australia, including
Tasmania. Arrows indicate the influence
of adjacent bioregions, i.e. Flindersian
(western warm temperate) and Peronian
(eastern warm temperate).
islands of the central (Kent and Hogan groups), eastern
(Furneaux Group) and western (King Group) Bass Strait, and
mainland Tasmania, including its adjacent islands (see Fig. 2). A
temporal reconstruction of the coastal ichthyofauna was synthesized from a rich variety of sources because a complete time
series of distribution and abundance data is lacking. Data were
accessed from historical documents (published manuscripts,
checklists and books), spearfishing competition results, field
surveys, commercial fishing records, underwater observations,
photographic records and other unpublished anecdotal information. Data sources varied in type, content, completeness and
validity, but when combined, provided a robust overview of the
composition and general distribution of species during each
period. This information was summarized to produce distributional dossiers on candidate species for each of three periods:
‘late 1800s’ (1880–1925), ‘1980s’ (1970–85) and ‘present’
(1995–now) – a summary of these data is provided in
Appendices S1–S3 in the Supporting Information and will be
made available from the Tasmanian Coastal Climate Change
Range Expansion Database and Mapping project (REDMAP) at
http://www.redmap.org.au/. Common names of species referred
to in this study follow the Australian Fish Names standard
(Yearsley et al., 2006; http://www.seafood.net.au). Main datasets
relevant to each period are discussed briefly below.
‘Late 1800s’
Coastal fish communities were not exploited by indigenous
people (Luckman & Davies, 1978) and prior to the arrival of
Europeans in the early 1800s were likely to be near pristine. By
the mid 1800s, most distributional information on Tasmanian
fishes had been obtained incidentally by naturalists. Soon after,
fishing activities inshore increased dramatically and some populations soon displayed evidence of localized depletion
(Johnston, 1883). Based on his own research and using an
unpublished manuscript list (compiled by a local naturalist, M.
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Allport), Johnston compiled the first annotated checklists of
Tasmanian fishes. His work was thorough and comments on
occurrence and commonness were provided for most of the 188
species known to exist in the region. This list was soon superseded by a revised version which included 214 species
(Johnston, 1890). Johnston’s studies are particularly relevant to
this investigation as data were obtained primarily from coastal
assemblages, caught by beach seine, gillnet and hook and line,
with some additional information on offshore species taken by
pelagic fishing and bottom lining methods using hook, line and
lure. In 1923, Lord (1923) produced a revised checklist, including 259 species, which was supplemented by additional species
taken by exploratory trawl surveys of the region by the FRV
Endeavour. Soon afterwards, he published the first guide to vertebrates of the region (Lord & Scott, 1924), which included
notes on 262 fish species. These data have been summarized here
based on a nomenclatural history and our knowledge of the
contemporary fauna.
‘1980s’
The 1970s and first half of the 1980s were important periods for
the exploration of marine biodiversity in this region with several
surveys of inshore areas (e.g. Last, 1979; Edgar, 1984) and deeper
parts of the continental shelf and slope (e.g. Last & Harris,
1981). Compositions of Tasmanian coastal fish assemblages and
the distributions of their species were defined during the preparation of two regional guides (Edgar et al., 1982; Last et al.,
1983). The most valuable supporting data for these publications
came from field surveys, spearfishing competitions, fisheries statistics and underwater photographic records, the most important of which are documented below.
1. Field surveys. In 1982, Dr Barry Hutchins, an ichthyologist
from the Western Australian Museum, completed an underwater survey of Tasmanian fishes as part of a broader investigation of the ichthyofauna of southern Australia. This 2-month
Global Ecology and Biogeography, 20, 58–72, © 2010 Blackwell Publishing Ltd
Long-term shifts in a temperate fish fauna
survey was conducted in summer when seasonal vagrants are
most abundant in the region. He used a combination of ichthyopoison samples and underwater observations and photographs
to compile a list of about 140 species from 9 generalized sites
located around the coastline of Tasmania. This survey led to the
discovery of new cryptic species and provided important distributional information on the coastal ichthyofauna. Dr Hutchins
had an exceptional knowledge of temperate Australian inshore
fishes, so species missing from this survey are as important as
those recorded, because their absence suggests that they are most
likely either uncommon or absent on reefs in the region. Additional lists of species, based on underwater observations, were
published by two of the authors (Last, 1979; Edgar, 1984), who
also compiled additional distributional information on fishes in
Tasmanian waters.
2. Spearfishing competitions. Underwater fishing is an efficient
method of estimating the abundances of rare reef fishes
(Lincoln Smith et al., 1989); hence, catches from competitions
are a valuable but under-utilized historical data source. Catch
data, collated from 12 competition sites held in northern,
eastern and southern Tasmania in the 1970s, were pooled at each
site to provide a total catch and to determine species composition for each site. Pooled data represented effort from 315 diver
days (each about 4 h day-1) culminating in c. 1300 diver hours
and the collection of 2502 specimens of 50 coastal species; this
represents some 17% of the known Tasmanian coastal fish
fauna. Numerous factors may have influenced the likelihood of
capture for targeted species, including their presence at the site,
diver experience, suitability of local habitat and weather conditions. While failure to capture a species at any site cannot be
definitively interpreted as a non-occurrence, this sampling
method (competition scoring) is based on capturing as many
large species as possible, so moderately abundant and common
fishes are typically thoroughly represented and a selection of
rare species are usually also caught (Coll et al., 2004).
3. Underwater photographic records. The first photographic
guide to coastal fishes of Tasmania and the Bass Strait (Edgar
et al., 1982) was based on images taken by a local group of
underwater photographers and scientists. Fourteen members
of the Tasmanian Underwater Photographic Society dived
throughout the region over a 2-year period to source images of
as many species as possible; they captured images of 124 of the
290 coastal fishes then thought to occur in the region, as well as
obtaining important information on their distributions and
abundances. Effort data were not recorded but would have
amounted to several hundred diver hours. Hence, species not
photographed were considered to be cryptic, difficult to photograph or very rarely encountered during this period.
4. Complete regional guide. A guide to all 461 fishes then
known to occur in Tasmanian waters was prepared soon after
(Last et al., 1983). Much of the data were obtained through the
sources described above, as well as government funded fishery
surveys and personal records of commercial and recreational
fishermen. Hence, notes on the local distributions and abundances of species, where specified, were used to characterize and
summarize the fauna in the ‘1980s’.
‘Present’
Our ‘present’ knowledge of the coastal ichthyofauna is based on
fishery catches (both commercial and recreational), diver observations and information provided by scientists, scuba divers and
recreational and commercial fishers to REDMAP. Species distributions have been mapped in bioregionalization studies for
regional marine planning of the Australian EEZ (IMCRA, 1996),
and their biogeographic affinities have been determined from
these datasets, which are held within the Codes for Australian
Aquatic Biota (CAAB) database (http://www.cmar.csiro.au/
caab/). Broader-scale information on the distribution of warm
temperate species was obtained from important regional guides
(Hutchins & Swainston, 1986; Gomon et al., 2008). Newly
recorded species and those with changes in the distributional
profiles were identified; these included species with recently
established breeding populations in Tasmanian waters, latitudinal range shifts and/or increases in abundance, or direct range
expansions in south-east Tasmania where the former range was
restricted or patchy. Eight classification categories (Table 1) were
used to characterize these changes.
Analysis
Data sources, as listed above, were used to compile a list of
Tasmanian fishes exhibiting temporal shifts in their distribution
and/or abundance. Information was initially assembled for the
entire fish fauna, with detailed data collation focused on the
coastal assemblages which are best represented across the three
time periods (i.e. ‘late 1800s’, ‘1980s’ and ‘present’). By combining available data we reconstructed change profiles for candidate
species at each of these time intervals and assigned them to one
or more of the eight main qualitative categories of distributional
change as defined in Table 1. These categories consider the
change status of species using the ‘1980s’ as a ‘control’ period
(preceding recent observed changes in the ‘present’ fauna), based
on whether species are new to the region, were once considered
rare, have recovering populations or now have expanded local
ranges and/or abundances (Categories 1, 3, 4, 6). A separate
category was provided for species exhibiting distributional
changes at the southern limit of the Tasmanian Province, the
Bruny bioregion (Category 5). Other species, which were
recorded from the ‘late 1800s’, disappeared from the fauna by the
‘1980s’ (Category 2) or are now threatened (Category 7); still
others only occur in the region as extra-limital vagrants (Category 8). Species missing since the ‘late 1800s’ were further
subdivided into those considered to be extinct locally, now confined to remnant populations, occurring periodically in the
region, or doubtful records (based on erroneous data or misidentifications such as confusion with sibling species).
Some species conform to more than a single category of
change. For example, a species may have experienced a serious
population decline since the ‘late 1800s’ to be considered as
locally extinct by the ‘1980s’ (Category 2a), but is now recovering
(Category 6) with significant changes in its regional abundance
since the ‘1980s’ (Category 4). Evidence of change was inferred
Global Ecology and Biogeography, 20, 58–72, © 2010 Blackwell Publishing Ltd
61
P. R. Last et al.
Table 1 Classification of distributional change in the Tasmanian coastal ichthyofauna and numbers of families and species of fishes in each
of these different categories based on the 37 families and 61 species with observed distributional and/or abundance changes.
Category
Definition
1. Previously rare or unlisted species
Not listed or very rare in the ‘1980s’ but now resident or becoming established;
primarily includes colonizers from biogeographic provinces to the north
Recorded in the ‘late 1800s’ but very rare or absent from the fauna by the ‘1980s’:
No longer occurs in the region
Remains in the region but with an extremely contracted or remnant distribution
Occurs periodically as mid-term residents (c. 2–10 years)
Likely misidentification; probably confused with sibling species
Resident exhibiting poleward range extension (usually southward) in part(s) of
Tasmania since the ‘1980s’; extra-limital vagrants were excluded from this group
Resident exhibiting an obvious abundance increase (usually southward) in part(s) of
Tasmania since the ‘1980s’; where they were once not well represented or rare
Rare or known from small populations in south-east Tasmania in the ‘1980s’ but
now with much broader ranges; this scenario is usually accompanied by a general
abundance increase
Recorded from the region in the ‘late 1800s’, absent or at low abundance in the
‘1980s’, and now increasing; climate change may not be the sole attribution of
change for these species
No discernible change in distribution before the ‘1980s’ but now extremely restricted
or declining in abundance and range
Previously unlisted transient species from tropical Australian biogeographic
provinces; probably migrated to Tasmania with the assistance of the East
Australian Current (EAC)
2. Missing species
a Local extinctions
b Remnants
c Periodical residents
d Doubtful records
3. Expanded ranges
4. Abundance increases
5. Expanding in the south
6. Recovering species
7. Now threatened species
8. Extra-limital vagrants
Families
from a detectable decline or increase in either abundance, frequency of occurrence or geographic range. A spreadsheet providing supporting information and a dossier for each candidate
species is provided in Appendices S1–S3.
The main faunal lists for the ‘late 1800s’ (Johnston, 1883; Lord
& Scott, 1924) and ‘1980s’ (Edgar et al., 1982; Last et al., 1983)
were used to assess the local distributional status for each species
during these time periods. Other historical data sources, discussed above, were used to iterate these assessments, and the
statuses of species is summarized in Appendix S4, according to
criteria outlined in Appendices S2 and S3. Secondly, distributional details were mapped for each species (Appendix S3) to
eight Tasmanian bioregions (IMCRA, 1996) for the ‘1980s’ and
‘present’. Abbreviations for variables, bioregions, levels of
change and the putative causes of change and their estimated
confidence levels are provided in Appendix S1. Historical ranges
of species in the ‘1980s’, based primarily on Hutchins & Swainston (1986), including specific distributional information
largely from Tasmania (Last et al., 1983) and lists from the ‘late
1800s’, are summarized in Appendix S2. Present ranges, where
they differ from the situation in the ‘1980s’, are compiled from
the broad variety of sources specified above (Appendix S2).
Other summary data compiled included primary habitat and
indices of commonness, occurrence and breeding status
(Appendix S3). Each species was also assigned to one of the
following classes based on their biogeographic affinities in the
Australian region (IMCRA, 1996): Bassian, primarily in the Bass
Strait; Tasmanian, restricted cold temperate Australian species;
62
Species
8
12
3
2
1
9
15
3
3
1
9
23
21
30
14
16
3
3
1
2
3
4
Flindersian, western warm temperate species; Peronian, eastern
warm temperate species; Southern Australia (S. Aust), widespread throughout temperate southern Australia; Tropical,
mainly widespread off northern Australia; Widespread, ubiquitous in Australian seas.
R ESULTS
Some 37 families (over a third) and about 61 species (about a
fifth) of the coastal ichthyofauna of Tasmania, which now consists of about 300 species, have, or appear to have, undergone
important compositional shifts over the three periods considered (i.e. ‘late 1800s’, ‘1980s’ and ‘present’) leading to overall
increased species richness and faunal complexity (Appendix S4). Changes were recorded in all eight of our classification
categories (Table 1). These changes include the loss or drastic
reduction in relative abundance of at least five large predatory
fishes, and possibly another 14 unresolved or restricted species,
treated in ‘late 1800s’ checklists (Johnston, 1883, 1890)
(Table 2). More recently, there is evidence of present-day distributional shifts in 52 species (c. 17% of the coastal fish fauna),
including the recent range extension of warm temperate species
from the north that were either previously rare or unrecorded
from the region (12 species), new extra-limital vagrants (4
species), those that now have expanded southern populations
(23 species), those that have extended their ranges in southeastern Tasmania (16 species) and/or increased their abundances in Tasmania (30 species) (Table 1). Of these, 45 species,
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Long-term shifts in a temperate fish fauna
Table 2 Coastal species recorded by Lord & Scott (1924) exhibiting major changes in their occurrence status over the three temporal
periods referred to in this study.
Name (Lord & Scott, 1924)
Current name (likely)
Status late 1800s
Status 1980s
Present status
Gyropleurodus galeatus
Carcharias arenarius
Orectolobus maculatus
Pseudobatrachus dubius
Histrio histrio
Brachionichthys hirsutus
Brachionichthys politus
Hemirhamphus intermedius
Trachichthys australis
Centropogon australis
Neosebastes panda
Sillago maculata
Trachurus novaezelandiae
Sparus australis
Sciaena antarctica
Dactylopagrus morwong
Latridopsis ciliaris
Achoerodus gouldii
Notolabrus celidotus
Heterodontus galeatus
Carcharias taurus
(Orectolobus halei)
Batrachomoeus dubius
Histrio histrio
Brachionichthys hirsutus
Sympterichthys politus
(Hyporhamphus melanochir)
Trachichthys australis
(Gymnapistes marmoratus)
(Neosebastes scorpaenoides)
(Sillago bassensis)
(Trachurus declivis)
(Acanthopagrus butcheri)
Argyrosomus hololepidotus
Nemadactylus valenciennesi
Latridopsis ciliaris
(Achoerodus viridis)
(Notolabrus tetricus)
Present
Not uncommon
Common
Present
Present
Not uncommon
Common and restricted
Seasonal
Probably common
Infrequent
Not common
Doubtful
Common
Common
Rare
Not common
Rare
Common
Present
Locally extinct
Locally extinct
Extremely restricted
Dubious record
Dubious record
Common and restricted
Restricted
Dubious record
Absent
Dubious record
Dubious record
Dubious record
Dubious record
Dubious record
Locally extinct
Possibly extinct
Locally extinct
Locally extinct
Dubious record
Locally extinct
Locally extinct
Extremely restricted
Dubious record
Dubious record
Rare and restricted
Extremely restricted
Dubious record
Recovering
Dubious record
Dubious record
Dubious record
Dubious record
Dubious record
Locally extinct
Recovering
Periodical resident
Recovering
Dubious record
Names in brackets are likely valid names of misidentifications.
representing 27 families (about 30% of the inshore fish families
occurring in the region), exhibited major distributional shifts
thought to be climate related. Changes in each of these categories are described further below.
Previously rare or unlisted species
Compositional knowledge of the Tasmanian fish fauna has
expanded since the ‘1980s’ as additional species are discovered.
Most recent additions to the checklist are fishes from the less
comprehensively explored deep sea or the open ocean. Noncryptic, coastal species are less likely to escape detection, so in
this region, which has been extensively surveyed, their recent,
simultaneous appearances are likely to reflect ‘real’ change.
Members of a group of 12 ‘previously rare or unlisted’ Tasmanian inshore fishes have expanded their distributions since the
‘1980s’ (Table 3). They include: three indigenous colonizing
species from the north (previously unlisted); six species whose
occurrence in the region in the ‘1980s’ was based on a few
specimens (rare or extremely restricted); and three species that
had become rare by the ‘1980s’ but are now recovering (see
‘Recovering species’ section below). There is no definitive evidence that any of these species have established self-sustaining
populations, but as most are present as either adults or in sizeable aggregations it is likely that some are capable of breeding in
the Tasmanian region.
Most new regional records of these species come from the
Furneaux Group and/or the eastern Tasmanian coast. A single
soft-bottom species, the eastern shovelnose stingaree (Trygonoptera imitata) (Fig. 3a), which is abundant along the north-
ern Bass Strait coast, has established populations in the
Furneaux Group. This genus was not previously represented in
Tasmanian waters. All other species are reef dwellers, over a third
are wrasses (Labridae), and seven are Peronian species that are
dominant members of a fish assemblage normally associated
with barrens formed by the longspine sea urchin (Centrostephanus rodgersii).
Missing species
Distributional information from the ‘late 1800s’ (Johnston,
1883; Lord & Scott, 1924) varies in its detail, but at least 16
species ‘went missing’ from the Tasmanian fauna before the
‘1980s’ (Last et al., 1983), and another three recovering species
suffered major declines in their ranges (Table 2). The group of
‘missing species’ includes three species that are now considered
to be extinct locally, three with remnant distributions, a periodical resident and another nine species whose listings appear
to be based on misidentifications and doubtfully occur in the
region.
Large predatory fishes, such as the greynurse shark (Carcharias taurus) (Fig. 3b), crested hornshark (Heterodontus galeatus)
and mulloway (Argyrosomus hololepidotus), have not been
observed in Tasmanian waters for nearly a century so we considered them to be extinct locally; whereas other large predators,
the queen snapper (Nemadactylus valenciennesi) and eastern
blue groper (Achoerodus viridis) (Fig. 3f), are now showing weak
signs of recovery. These are all distinctive fishes, mostly well
regarded as recreational or commercial species, and are unlikely
to have been overlooked if present.
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P. R. Last et al.
Table 3 Coastal species previously unlisted (U), rare (R) or extremely restricted (R&R) in Tasmanian seas during the ‘1980s’ that are now
more widespread or recovering (RE); includes their biogeographic affinity, location observed, occurrence, primary habitat type, association
with longspine sea urchin barrens and local breeding status.
Scientific name
Status
Biogeographic affinity
Location
Occurrence
Habitat
Trygonoptera imitata
Aplodactylus lophodon
Notolabrus gymnogenis
Achoerodus viridis
Trachichthys australis
Nemadactylus valenciennesi
Gymnothorax prasinus
Latropiscus purpurissatus
Nemadactylus douglasii
Chromis hypsilepis
Ophthalmolepis lineolatus
Eupetrichthys angustipes
U
U
U
RE
RE
RE
R
R
R
R&R
R&R
R&R
Bassian
Peronian
Peronian
Peronian
S. Aust
Flindersian
S. Aust
S. Aust
Peronian
Peronian
Peronian
Peronian
Flinders
C Bass
S Bass
S Bass/NE
Flinders
W
NE
S Bass
NE
E
E/SE
NE/SE
Localized
Patchy
Patchy
Patchy
Common
Patchy
Patchy
Patchy
Common
Patchy
Patchy
Patchy
Soft bottom
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Urchin barrens
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Breeding
Yes?
No
No
No
Yes?
Yes?
Yes?
Yes?
Yes?
Yes?
Yes?
Yes?
? = unconfirmed.
Location: C Bass, central Bass Strait islands; E, east; Flinders, Flinders Island; NE, north-east; S Bass, southern Bass Strait; SE, south-east; W, west.
The blue moki (Latridopsis ciliaris) is primarily a New
Zealand species that appears to recruit periodically across the
Tasman Sea into southern Australian waters (Yearsley et al.,
1999). It was recorded from Tasmanian waters in the late 1880s
(Johnston, 1890) but its occurrence locally was questioned by
Lord & Scott (1924). The species was omitted from Last et al.
(1983) because there had been no confirmed records from the
20th century despite a comprehensive search for information or
specimens. However, soon after (c. 1985), juveniles were presented to the senior author from eastern Tasmania, presumably
following a large spawning event in the Tasman Sea. Sightings of
juveniles were frequent in the late 1980s but this cohort disappeared shortly after an adult fish was captured in southern
Tasmania in the early 1990s. This species has not been recorded
from the region since, suggesting that its occurrence in the
region is periodical.
Three species occur in remnant populations that have not
recovered in recent times. A wobbegong (assumed to be the gulf
wobbegong, Orectolobus halei) was considered common by
Johnston (1883), but by the ‘1980s’ was confined to a handful of
resident adults, observed regularly at a very small, isolated reef
off Flinders Island (Furneaux Group). According to local divers
this population still exists (c. 2009) but its range has barely
expanded beyond this patch. Similarly, two handfishes have suffered serious range reductions and are now threatened (see ‘Now
threatened species’ section below).
The ‘late 1800s’ lists contain records (nine taxa) that are
doubtful and probably resulted from the erroneous application
of names to well-known Tasmanian species; most of these are
names of close relatives or sister species. However, three distinctive fishes, the eastern frogfish (Batrachomoeus dubius), the
sargassum fish (Histrio histrio) and the eastern fortescue
(Centropogon australis), are not easily confused with other local
species and may have once existed in the region; three of these
genera are not otherwise recorded locally.
64
Species with an expanded range
Twenty-three species display recent southward shifts in their
range limits, and about half of these (12 species) also show
subtle increases in their abundances within their extended
ranges (Table 4). Almost all of these fishes are reef dwellers
(91%) and about half are dominant coastal elements of the
Peronian Province (11 species); other biogeographic groups
include widespread southern Australian (seven species), Flindersian (four species) and Bassian (single species) fishes. This
pattern exists in 14 families with labrids (four species) and
kyphosids (three species) being the most important groups.
Warm temperate surf-zone fishes, the silver drummer (Kyphosus
sydneyanus) (Fig. 3c) and rock blackfish (Girella elevata), which
once had very restricted distributions in the region (Last et al.,
1983), are now more abundant in the north and east, particularly in the Furneaux Group where schools of G. elevata sometimes include gravid individuals. Girella elevata is one of the five
most commonly speared fishes in competitions off Sydney
(Lincoln Smith et al., 1989). Other reef species, such as the
onespot puller (Chromis hypsilepis), the snakeskin wrasse
(Eupetrichthys angustipes) and the southern Maori wrasse (Ophthalmolepis lineolatus), which were restricted locally to the Kent
Group (central Bass Strait), have now been recorded from
several localities to the south. While seven species have broadened their ranges in Bass Strait (four in the southern Bass Strait,
two off Flinders Island and one off the central Bass Strait
islands), the most striking expansions occur along the southeast (12 species) and/or east (five species) coasts.
A large cheilodactylid, the blue morwong (Nemadactylus
valenciennesi), is now caught infrequently off the northern west
coast and remains the only species known to display a poleward
shift off the west coast. Weaker trends in this largely remote
region probably reflect poorer sampling effort rather than stability in community structure.
Global Ecology and Biogeography, 20, 58–72, © 2010 Blackwell Publishing Ltd
Long-term shifts in a temperate fish fauna
Figure 3 Underwater photographs representing species from each of the eight change categories: (a) eastern shovelnose stingaree
(Trygonoptera imitata), a previously unlisted species; (b) greynurse shark (Carcharias taurus), a missing species; (c) silver drummer
(Kyphosus sydneyanus), an expanded range species; (d) Castelnau’s wrasse (Dotalabrus aurantiacus), a species with an increased abundance;
(e) snapper (Pagrus auratus), a species with expanded range in south-eastern Tasmania; (f) eastern blue groper (Achoerodus viridis), a
recovering species; (g) spotted handfish (Brachionichthys hirsutus), a now threatened species; (h) Queensland groper (Epinephelus
lanceolatus), an extra-limital vagrant. Photographs (b), (e), (f) and (h) were taken outside Tasmanian seas.
More abundant species
Thirty species exhibit an increase in abundance in some part of
their Tasmanian range (Table 4). This group comprises families,
with more than half being perch-like fishes (c. 63%) and a sixth
elasmobranchs (c. 17%). Generalized increases were observed
across the region: Tasmania-wide (four species), southern Bass
Strait and north-east (12 species), east (nine species), south-east
(13 species) and west (one species). Twice as many species
appear to have undergone abundance increases along the
eastern coast (23 species) as along the northern coast (12
species). These species occur in a mixture of habitats but twothirds are reef fishes (20 species) with a smaller mix of soft
bottom (four species), seagrass (three species), pelagic (two
species) and inshore demersal fishes (one species).
Half of the fishes in this category are warm temperate
Australian endemics and half of them are widespread in southern Australia (15 species). The warm temperate Peronian (eight
species) and Flindersian (seven species) provinces are about
evenly represented. At least 14 species (e.g. Atypichthys strigatus,
Global Ecology and Biogeography, 20, 58–72, © 2010 Blackwell Publishing Ltd
65
P. R. Last et al.
Table 4 Coastal species that have undergone recent poleward shifts and/or increases in abundance in Tasmanian waters, including the
location observed, biogeographic affinity, primary habitat type and local breeding status.
Scientific name
Heterodontus portusjacksoni
Trygonorrhina dumerilii
Dasyatis brevicaudata
Trygonoptera imitata
Urolophus paucimaculatus
Myliobatis australis
Gymnothorax prasinus
Latropiscis purpurissatus
Trachichthys australis
Platycephalus laevigatus
Hypoplectrodes maccullochi
Hypoplectrodes nigroruber
Pomatomus saltatrix
Seriola lalandi
Pagrus auratus
Girella elevata
Girella tricuspidata
Girella zebra
Kyphosus sydneyanus
Atypichthys strigatus
Scorpis aequipinnis
Scorpis lineolata
Enoplosus armatus
Chromis hypsilepis
Parma microlepis
Chironemus marmoratus
Aplodactylus lophodon
Cheilodactylus nigripes
Dactylophora nigricans
Nemadactylus douglasii
Nemadactylus valenciennesi
Achoerodus viridis
Dotalabrus aurantiacus
Eupetrichthys angustipes
Notolabrus gymnogenis
Ophthalmolepis lineolatus
Haletta semifasciata
Heteroscarus acroptilus
Odax cyanomelas
Eubalichthys mosaicus
Omegophora armilla
Shift
Abundance increase
Biogeographic affinity
Habitat
Breeding
S Bass
SE
S Bass
SE
S. Aust
Flindersian
S. Aust
Bassian
S. Aust
S. Aust
S. Aust
S. Aust
S. Aust
Flindersian
Peronian
S. Aust
S. Aust
S. Aust
S. Aust
Peronian
Peronian
Flindersian
S. Aust
Peronian
Flindersian
Peronian
S. Aust
Peronian
Peronian
Peronian
Peronian
Flindersian
Flindersian
Peronian
Flindersian
Peronian
Flindersian
S. Aust
Peronian
Peronian
S. Aust
S. Aust
S. Aust
S. Aust
Peronian
Reef
Soft bottom
Soft bottom
Soft bottom
Soft bottom
Soft bottom
Reef
Reef
Reef
Seagrass
Reef
Reef
Pelagic
Pelagic
Inshore
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Reef
Seagrass
Reef
Reef
Reef
Seagrass
Reef
Reef
Reef
Reef
No
No
No?
Yes?
Yes
No?
Yes?
Yes?
Yes?
Yes
Yes?
Yes?
No
No
No
Yes
Yes
Yes
No?
Yes
Yes
Yes
Yes
Yes?
No
Yes
No
Yes
Yes
Yes?
Yes?
No
Yes
Yes?
No
Yes?
Yes
Yes
Yes
No
Yes
Flinders
S Bass
Flinders
SE
SE
SE
SE
SE
SE
E
E
SE
SE
SE
NE
S Bass
Flinders
SE
S Bass
S Bass
Tas
Tas
Tas
N/E
SE
E/SE
NE
N/E
E/SE
N/E
Tas
C Bass
E/SE
E/SE
W
NE
NE
W
E/SE
NE/SE
S Bass
E/SE
E/SE
SE
S Bass
E/SE
E/SE
S Bass
SE
? = unconfirmed.
Location: C Bass, central Bass Strait islands; E, east; Flinders, Flinders Island; N, north; NE, north-east; S Bass, southern Bass Strait; SE, south-east; Tas,
Tasmania; W, west.
Scorpis lineolata, Dotalabrus aurantiacus (Fig. 3d) and Haletta
semifasciata) now occur as both adults and juveniles where their
abundances have recently increased, and are likely to be breeding
at these locations (Table 4). However, another six species (i.e.
Pagrus auratus (Fig. 3e), Pomatomus saltatrix, Seriola lalandi,
Eubalichthys mosaicus, Heterodontus portusjacksoni and Trygonorrhina dumerilii), are either known to breed elsewhere or are
unlikely to breed in Tasmanian waters.
66
Species with expanded populations in the south-east
Sixteen species appear to have expanded their ranges in southeast Tasmania by exhibiting either a broader distribution or
general increase in abundance in the Bruny bioregion (Table 5).
These fishes are generally large to medium-sized, with elasmobranchs well represented (four species). Most were known from
the bioregion in the ‘late 1800s’ and ‘1980s’, but were typically
Global Ecology and Biogeography, 20, 58–72, © 2010 Blackwell Publishing Ltd
Long-term shifts in a temperate fish fauna
Table 5 Coastal species previously known from south-east
Tasmania that have recently expanded their range and/or
abundance in this region, classified by biogeographic affinity,
primary habitat type and local breeding status.
Scientific name
Biogeographic
affinity
Habitat
Breeding
Heterodontus portusjacksoni
Dasyatis brevicaudata
Urolophus paucimaculatus
Myliobatis australis
Pomatomus saltatrix
Seriola lalandi
Pagrus auratus
Haletta semifasciata
Odax cyanomelas
Platycephalus laevigatus
Girella zebra
Scorpis aequipinnis
Cheilodactylus nigripes
Dotalabrus aurantiacus
Girella tricuspidata
Omegophora armilla
S. Aust
S. Aust
S. Aust
S. Aust
S. Aust
S. Aust
S. Aust
S. Aust
S. Aust
Flindersian
Flindersian
Flindersian
Flindersian
Flindersian
Peronian
Peronian
Reef
Soft bottom
Soft bottom
Soft bottom
Pelagic
Pelagic
Inshore
Seagrass
Reef
Seagrass
Reef
Reef
Reef
Seagrass
Reef
Reef
No
No
Yes
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
more widespread and abundant in the Bass Strait than in areas
to the south.
The level of range expansion in this bioregion varies between
species. For example, the smooth stingray (Dasyatis brevicaudata) has gone from being an occasionally occurring, seasonal
transient to a more widely distributed species that is abundant
and possibly resident at some locations. The rock flathead
(Platycephalus laevigatus), abundant in parts of the Bass Strait
but missing from the west and east, was represented in the
south-east in the ‘1980s’ by a small extra-limital population in
one small embayment; it has now expanded its range to become
widespread throughout large sheltered bays of the south-east.
Reef species, such as the sea sweep (Scorpis aequipinnis) and
herring cale (Odax cyanomelas), which were typically abundant
only in the Bass Strait, are now widespread on reefs along the
eastern and south-eastern coastlines.
The snapper (Pagrus auratus) was thought to be confined to
the north and east coasts in the ‘late 1800s’ (Lord & Scott, 1924).
However, while they have been caught infrequently by local
fishermen in the south in recent decades, their abundance
appears to have increased widely across their entire range and
they are now targeted by fishers in parts of southern Bass Strait
and the Furneaux Group.
Abundances appear to have increased for all 16 species near
the southern limits of their ranges. This assemblage consists of
nine widespread southern Australian, five Flindersian and two
Peronian species. These fishes occupy a variety of niches exhibiting preferences for either soft bottoms, seagrasses, reefs or
inshore demersal habitats. Coexisting adults and juveniles indicate that at least 10 of these species are now likely to breed in the
bioregion.
Recovering species
A small group of species, which were once well represented in
the region based on early historical information but were
missing or represented by remnant populations during the
‘1980s’, are now showing signs or recovery or have re-recruited
to the region. These species include: Trachichthys australis,
Nemadactylus valenciennesi and the eastern blue groper, Achoerodus viridis (Fig. 3f). The recent rediscovery of juveniles of A.
viridis, a major predator of urchins, in the north and north-east,
may have important ecological implications in the future. This
large wrasse was once considered to be a ‘common species
around the rocky section of the coast’ (Lord & Scott, 1924), but
was later excluded from the Tasmanian fish fauna (Last et al.,
1983) as it had not been seen for more than 50 years and was
considered to be extinct locally. The long-term survival of N.
valenciennesi and A. viridis in the region is likely to be dependant
on the implementation of prudent management plans associated with fishing.
Similarly, the unmistakable cave-dwelling southern roughy
(Trachichthys australis), which was said to ‘inhabit rocky
reefs’ (Lord & Scott, 1924) but was not observed during
extensive underwater surveys around Tasmania in the ‘1980s’,
is now common off Flinders Island (P. Nichols, personal
communication).
Now threatened species
Handfishes (family Brachionichthyidae), which are endemic to
Australia, are represented by at least 14 small species, and all but
three of these occur in Tasmanian seas (Last & Gledhill, 2009).
Two species, Brachionichthys hirsutus (Fig. 3g) and Sympterichthys politus, both occurred in healthy populations in the ‘1980s’,
primarily in the south-east, but have now undergone serious
population declines and are now listed as threatened (e.g. Last
et al., 2007). Data are insufficient to ascertain the cause(s) of
these declines, but appear, at least in some instances, to be
related to critical habitat loss or damage.
Extra-limital vagrants
Four widely distributed transient species represent new records
for the Tasmanian region. All of these fishes occur in tropical
seas, and while two of them are typically pelagic, all occur in
coastal habitats elsewhere in Australia, e.g. the Queensland
groper (Epinephelus lanceolatus) (Fig. 3h). There are few historical records of the tiger shark (Galeocerdo cuvier) from south of
Sydney but there have been several captures in the last decade off
north-east Tasmania. Tropical vagrants are rare in the listed
fauna (11%), so the recent arrival of these species is not inconsistent with a southward distributional shift in composition.
While all of these species were of reproductive size, they are
unlikely to breed in southern seas. Another tropical offshore
demersal species, the thorny tinselfish (Grammicolepis brachiusculus), was also captured from the region in 2003.
Global Ecology and Biogeography, 20, 58–72, © 2010 Blackwell Publishing Ltd
67
P. R. Last et al.
D I SC U SSI O N
The effects of climate change on marine communities can be
manifested as shifts in the latitudinal distributions of species.
However, not all latitudinal boundaries are set by climate, and
localized hydrographic features need to be considered (Helmuth
et al., 2006). Oceanographic models have demonstrated that
climate change is highly likely to cause the EAC flow to
strengthen and extend southward, in turn resulting in further
warming of the Tasman Sea. Increasing sea surface temperatures
over the last 60 years off eastern Tasmania are primarily the
result of changes in the EAC rather than global surface fluxes
(Ridgway, 2007). The surface temperatures in the time-scale
examined by Ridgway (2007) equate to an increase of about
2.3°C/100 years and a corresponding poleward advance by the
EAC of about 350 km. Over the time-scale of this investigation
(‘late 1800s’ to ‘present’) there have been strong increases in
water temperature, above the long-term average for the region,
in each decade since 1970 (Fig. 1). Increased water temperatures
in the Tasman Sea are likely to have a cascading effect through
local marine ecosystems, probably most evident in, but not
exclusive to, inshore marine ecosystems. For example, biological
responses to these changes have been recorded off the east coast
of Tasmania for sea urchins (Ling et al., 2009) and shore crabs
(Thresher et al., 2003).
Long-term empirical data on the distributions of marine
biota collected using comparative methods are rarely available.
In their absence, we are forced to make best use of often disparate and largely non-quantitative data sets – in our case mixtures
of literature, field, photographic and other observational
records, which together provide a useful basis for comparing
distributional patterns. The strength of our argument in identifying change rests on the quality and reliability of accumulated
information for each of the three periods, particularly the
‘1980s’, which we consider to be a tipping point for potential
changes. These data were compiled from a period of high scientific activity where consistent absences of non-cryptic species
across the region are reliable indicators of extreme rarity or
non-occurrence. As discussed above, the argument for ‘real’
change is based on the regularity of this pattern, shared across
supraspecific taxa.
Our synthesized data strongly support changes in ichthyofaunal distribution over the span of three decades (‘1980s’ to
‘present’). Multiple cases of latitudinal shifts in geographic
range, and corresponding increases in abundances of 52 Tasmanian coastal fish species, provide strong inferential evidence of a
changing environment (Root et al., 2003). Stuart-Smith et al.
(2009) concluded that there has been no major change in the
structure of Tasmanian reef communities in the last decade, but
did note that some species changed in abundance; one of these,
Scorpis lineolatus, exhibited a five-fold increase in abundance.
We report changes over longer time-scales than those of StuartSmith et al. (2009), including species now present that were once
considered rare or unrecorded from the region, others primarily
confined to Bass Strait that have become resident or occur frequently further south, as well as those that now have expanded
68
populations and ranges in the south-east. Also, a small suite of
previously unrecorded vagrants from tropical habitats has been
recorded, providing further evidence of climate-induced
change.
A large proportion of the species (c. 40%) showing distributional and/or abundance changes in Tasmanian waters have
widespread distributions encompassing all of the southern Australian biogeographical provinces (see IMCRA, 1996). These
species are successful inhabitants of warm temperate Australian
seas and are likely to become better represented off Tasmania as
sea temperatures increase. Eight species (17%) exhibiting distributional and/or abundance changes in Tasmanian waters are of
a Flindersian (western warm temperate) origin. All of these
species displayed either abundance increases or a southward
range expansion, but only one had been recorded previously as
rare in Tasmanian waters (Tables 3 & 4). Twelve species with
Peronian (eastern warm temperate) affinities appear to have
shifted their ranges in association with the recent southward
extension of the longspine sea urchin (Centrostephanus rodgersii). However, an additional five species with Peronian distributions, but not associated with barrens created by these urchins,
have recently expanded their ranges in Tasmanian waters. Interestingly, only two of the species with expanded ranges and/or
abundances in south-eastern Tasmania (the Bruny Bioregion)
are Peronian species. Only one Bassian (Bass Strait) species,
Trygonoptera imitata, has extended its range southward into
Tasmanian waters.
Colonizing species might be expected to first appear closest
to the source of recruitment from adjacent regions. Hence, the
Bass Strait Islands act as ‘stepping stones’ or distributional pathways south. In the ‘1980s’, three typical Peronian species
(Chromis hypsilepis, Ophthalmolepis lineolatus and Eupetrichthys
angustipes) were confined to the Kent Group (central Bass
Strait), but all of these now have expanded ranges east and
south. Other southern Bass Strait species have extended their
ranges southward along the east coast, and often into bays of the
south-east.
Breeding range data, definitive evidence that species are established or resident in a region rather than extra-limital or transient, is not widely available for Australian fishes. However,
populations of some species (e.g. Girella elevata), until only
recently considered to be rare in the region, have been observed
with gravid individuals (P. Last, unpublished data). Other nonmigratory species (e.g. Urolophus paucimaculatus, Haletta semifasciata) presumably breed within their new extended ranges as
they now occur there as both adults and juveniles. These species
are not known to undertake long migrations so their adult
populations, which are often widely separated, are unlikely to be
connected reproductively; this is particularly evident for Bass
Strait fishes that have disjunct populations in the south-east.
Not all the changes observed can be attributed to climate
change. Most changes in faunal structure before the ‘1980s’ are
likely to be due to anthropogenic rather than environmental
factors. Some apical predators, including sharks (e.g. Carcharias
taurus, Orectolobus halei) and large teleosts (e.g. Argyrosomus
hololepidotus, Nemadactylus valenciennesi, Achoerodus viridis),
Global Ecology and Biogeography, 20, 58–72, © 2010 Blackwell Publishing Ltd
Long-term shifts in a temperate fish fauna
appear to have experienced serious range reductions or regional
extirpation since the 1880s. Johnston (1883) observed that
estuaries of the south-east once contained an abundance of
commercial fishes and juveniles of other species. However,
unprotected areas near population centres were soon ‘rendered
almost barren’ by intensive beach seining. At the same time, the
graball (a type of gillnet), was used to catch reef fishes in nearby
bays and over shallow reefs, and this method is still used by both
commercial and recreational fishers in Tasmania (Metcalf et al.,
2008). Edgar & Barrett (1999) have shown that large fishes are
particularly vulnerable to gillnetting practices; hence, this
method is likely to be destructive to fish communities over long
time intervals. While inconclusive, it is likely that apparent periodic or regional extinctions of large sharks and teleosts during
the 1900s were due primarily to the effects of fishing.
Some of the species putatively impacted are particularly vulnerable to certain fishing practices (Pogonoski et al., 2002). By
1969, populations of eastern blue groper (Achoerodus viridis)
had been seriously reduced off New South Wales and a total ban
on their capture was implemented in 1980 because large catches
were being taken by commercial gillnets (Pogonoski et al.,
2002). This species, which was marketed in Tasmania in the
1800s (as adults exceeding 1 m) and described as common in the
1920s, subsequently went missing until a few juveniles were
discovered off the northern coast in 2004. However, the likelihood of A. viridis re-establishing breeding populations in Tasmania is low; males take about 10 years to mature (Gillanders,
1995) and are unlikely to reach this stage due to fishing pressure
unless protective measures are implemented.
Elasmobranch fishes are particularly vulnerable to some
fishing methods, particularly gillnetting (Walker et al., 2005). Of
the 10 species exhibiting some form of change in Tasmanian
waters, one is a new record, one is a seasonal vagrant, five have
expanded their ranges or increased their abundance and three
appear to have suffered significant population declines. Elasmobranchs have K-selected life-history strategies (i.e. they have low
productivity, low fecundity, mature at a late age and are slow
growing), making them especially vulnerable to threatening
processes such as intense fishing pressure (Stevens et al., 2000).
The IUCN Species Survival Commission recognized this issue
and established the Shark Specialist Group (SSG) to provide
assessments for all sharks and rays as part of their Red List of
Threatened Species® program (IUCN, 2008). Two sharks appear
to have undergone significant population declines in Tasmanian
waters. Carcharias taurus is listed as vulnerable by the IUCN Red
List due to its extremely low reproductive rates and population
declines recorded off eastern Australia and South Africa (Pollard
& Smith, 2000). Catches of wobbegong sharks (including
Orectolobus halei) off south-eastern Australia, particularly
New South Wales, have declined markedly in recent decades
(Huveneers et al., 2007). These declines resulted in populations
of two wobbegong species in New South Wales initially being
listed as Vulnerable by the IUCN Red List (Cavanagh et al.,
2003). Thus, it is likely that threatening processes acting on these
species have significantly reduced, or possibly eliminated, the
populations of these sharks in Tasmanian waters.
Fishery impacts are also evident in offshore assemblages.
Commercial fishes, the gemfish (Rexea solandri) and blue-eye
trevalla (Hyperoglyphe antarctica), which typically occur in deep
water along the continental slope, were once caught trolling at
the surface off south-east Tasmania (Lord & Scott, 1924). In the
case of gemfish, populations have been subjected to overfishing
off south-eastern Australia (Punt & Smith, 1999) and this
species is no longer abundant, even in its primary habitat. Thus,
a number of the changes to components of the fauna of this
region are best attributed to non-climate stressors.
We have highlighted examples of both non-climate and
climate-related impacts on a wide diversity of fishes in this
study, with 27 families (including six elasmobranch families)
displaying recently altered distributions off Tasmania. The
majority of species showing distributional and/or abundance
changes in Tasmanian waters are reef-dwellers (66%). Most of
these families are represented by a single species, but there
are multiple species from the families Cheilodactylidae,
Kyphosidae, Labridae and Serranidae, of which all but one are
reef dwellers. Previous studies have shown that reef fishes are
useful indicators of environmental change (e.g. Holbrook et al.,
1997); however, changes are also evident within the pelagic
fauna. The frigate mackerel (Auxis thazard) was recorded in the
1800s but has been rarely seen in Tasmanian waters, until
schools were observed recently off north-eastern Tasmania.
Anecdotal information provided by recreational fishers indicates that abundances of other warm water tunas and billfishes
have increased in recent years.
While there have been major range shifts in some dominant
coastal fishes, particularly those that occur primarily in the Bass
Strait, many other species have not undergone any obvious distributional shift. For example, no distributional changes have
been observed for the common Bass Strait reef species, the
horseshoe leatherjacket (Meuschenia hippocrepis), the yellowstriped leatherjacket (Meuschenia flavolineata), the pencil weed
whiting (Siphonognathus beddomei) and the scalyfin (Parma
victoriae), and a soft-bottom species, the southern bluespotted
flathead (Platycephalus speculator). The absence of poleward
movement in these taxa, despite obvious shifts in other
co-occurring species, suggests that it is difficult to predict which
species will exhibit induced range shifts. In situ changes in abundance, physiology or phenology (Hobday et al., 2007) of these
species may still mean that climate change is having an impact,
but without more detailed study impacts remain unknown. The
distributions of these important, non-cryptic species need to be
monitored in the coming years to assess their future responses to
environmental change.
While we have focused on changes in fish distributions,
habitat shifts in response to environmental change can also have
a considerable cascading effect in a biological community; an
example of this off the Tasmanian coastline is the longspine sea
urchin. This shallow-water urchin, which is found also off
northern New Zealand and the Kermadec Islands (Andrew &
Byrne, 2007), has a primarily Peronian-derived distribution in
Australia. Before 1978, it was only known in Tasmanian waters
from the central northern Bass Strait but is now established
Global Ecology and Biogeography, 20, 58–72, © 2010 Blackwell Publishing Ltd
69
P. R. Last et al.
along most of the east coast of Tasmania, a change attributed to
a strengthening of the EAC and associated ocean warming (Ling
et al., 2009). Newly formed urchin barrens are likely to result
from both climate change and reduced predation pressure associated with commercial harvesting of the urchin’s key predator,
the southern rock lobster (Jasus edwardsii). Our study indicated
that 7 of the 12 species that were rare, previously unlisted or
recovering in Tasmanian waters are strongly associated with
Centrostephanus rodgersii barrens (Table 3). Of these seven
species, six have a Peronian origin, providing strong circumstantial evidence that these species have shifted their distributions
southward in relation to latitudinal shifts in the distribution of
C. rodgersii or its associated barrens. Latitudinal shifts in the
distribution of biological facies and their associated biota have
not been well researched, but some coralline algal communities
also appear to have expanded their ranges southward in recent
years (P. Last, unpublished data).
Other non-climate-related change within the fauna is exemplified by a small group of introduced species. Two New Zealand
coastal reef fishes, the triplefins Forsterygion gymnota and Forsterygion varium, were introduced into the Derwent Estuary and
D’Entrecasteaux Channel, south-eastern Tasmania (Clements
et al., 2000). These species were initially thought to be
Tasmanian endemics (Last et al., 1983). At least four New
Zealand marine invertebrate species have been introduced into
Tasmanian waters, probably with shipments of live oysters
around the 1920s (Edgar, 1997), and the triplefins may have
been transported in the same way.
The importance of habitat availability should not be underestimated when attempting to predict the responses of species to
environmental change. The flathead Platycephalus laevigatus, a
Flindersian species, has expanded its range in the bays of southeast Tasmania and is now more widespread and abundant in
seagrass habitats of this region. However, despite these changes,
it has never been recorded off the central east coast, possibly as
a consequence of the unavailability of appropriate habitat. Thus,
future changes in faunal distribution may occur, not only in
response to direct changes in the physical environment (water
temperature) but to indirect changes in preferred habitat
(Hobday et al., 2007).
C O N C L U SI O N S
This paper set out to investigate two hypothetical changes in the
ichthyofauna off Tasmania in the south-eastern Australia
climate change hotspot. We hypothesized that the coastal fish
assemblages have exhibited a marked change in composition
since the ‘1980s’. The results of this study showed that about a
fifth (61 species) of the Tasmanian coastal fish fauna have, or
appear to have, undergone important compositional shifts since
the 1800s. Examination of longer-term fish composition data
revealed substantial changes to the coastal ichthyofauna of Tasmania, strongly supporting the first hypothesis. In addition, to
illustrate that not all change might be climate-related, we
hypothesized that certain elements of the Tasmanian ichthyofauna have been lost or severely depleted since the ‘late 1800s’. At
70
least five, possibly up to 19, species have undergone serious
declines and are possibly extinct locally. Localized extinctions,
particularly of apical predators such as the greynurse shark and
mulloway, are likely to be attributed to fishing pressure. Other
species, such as the gulf wobbegong, now have extremely
restricted distributions and are likely to face a similar fate
without intervention. Thus, the fauna of this region was not
‘pristine’ before this new invasion associated with warmer temperatures began.
This paper highlights, however, that many warm temperate
species have colonized the cool temperate Tasmanian region or
substantially expanded their ranges, consistent with a strengthening of the EAC and associated rises in sea temperature.
Although climate change is considered beneficial to a number of
species, it will also be detrimental to others (Poloczanska et al.,
2008). The effect of environmental change on species endemic
to cool temperate Australia has not been fully investigated, but
the lack of refugia south of Tasmania (i.e. the southernmost
limits of the Australian continental shelf), especially for coastal
species with population centres in southern Tasmania, is of
concern and should be a focal point of future research. Reliable
baselines are needed to evaluate further change, and to that end,
recent bioregionalization studies using national fish datasets
(e.g. IMCRA, 1996) can be used for this purpose. Similarly,
long-term scientific and community-based monitoring will be
important in documenting changes in the composition of
marine ecosystems. The paucity of documented impacts of
climate change in the marine realm of the Southern Hemisphere
is due to the resource-intensive and expensive nature of marine
monitoring (Richardson & Poloczanska, 2008). Volunteer
recording schemes, or ‘citizen science’ projects such as
REDMAP, allow for detailed monitoring to continue and
expand with comparatively little financial investment, but offer
scope for the generation of much-needed baseline data to
enhance monitoring efforts of science organizations.
AC K NO WL EDGEMENTS
Numerous colleagues, divers, fishers and the general public have
provided unpublished data and anecdotal records over a
number of decades. We acknowledge the wealth of information
that has been forwarded so enthusiastically from such sources.
In particular, we acknowledge assistance from professional fisherman Bill Smedley, and divers, including: Karen GowlettHolmes, Mike Nichols, Andrew Pender, Mike Sugden, Malcolm
Wells and numerous divers from the Australian Underwater
Federation. Neville Barrett (Tasmanian Aquaculture and
Fisheries Institute, TAFI), Barry Hutchins (formerly of the
Western Australian Museum) and Rick Stuart-Smith (TAFI)
have kindly provided unpublished data and advice. John
Pogonoski (CMAR) assisted with editing of the manuscript.
Alastair Graham and Louise Conboy (CMAR) have provided
assistance in the collation of data and collection support.
Thanks also to Nick Mooney and Ian Banks for use of underwater photographs. Finally, the authors wish to collectively
thank the three anonymous referees, as well as GEB editors
Global Ecology and Biogeography, 20, 58–72, © 2010 Blackwell Publishing Ltd
Long-term shifts in a temperate fish fauna
David Currie and Julian Olden, for providing constructive suggestions and comments on earlier drafts of this manuscript.
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SUPPO RTING INF O R MATIO N
Additional Supporting Information may be found in the online
version of this article:
Appendix S1 Abbreviations and keys to supporting
information.
Appendix S2 Summary data for candidate species detailing
changes in abundance and distribution.
Appendix S3 Summary of historical records and biogeographic
affinities of candidate species.
Appendix S4 Coastal species exhibiting distributional change in
Tasmanian waters since the ‘late 1800s’ and their current occurrence status and change category.
As a service to our authors and readers, this journal provides
supporting information supplied by the authors. Such materials
are peer-reviewed and may be reorganized for online delivery,
but are not copy-edited or typeset. Technical support issues
arising from supporting information (other than missing files)
should be addressed to the authors.
B IO SK ETC H
Peter Last is leader of the Biogeography and
Taxonomy team of CSIRO Marine and Atmospheric
Research in Hobart, Australia and is curator of the
Australian National Fish Collection (ANFC), with
interests in biogeography, systematics and phylogeny of
Indo-West Pacific marine fishes as well as bioregional
marine planning for the Australian region.
Editor: Julian Olden
Global Ecology and Biogeography, 20, 58–72, © 2010 Blackwell Publishing Ltd