Longterm Shifts in Abundance and Distribution of a Temperate Fish Fauna
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Global Ecology and Biogeography, (Global Ecol. Biogeogr.) (2011) 20, 58–72 RESEARCH Long-term shifts in abundance and PAPER distribution of a temperate fish fauna: a response to climate change and fishing practicesgeb_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 1Climate Adaptation Flagship, CSIRO Marine ABSTRACT and Atmospheric Research, GPO Box 1538, Aim South-eastern Australia is a climate change hotspot with well-documented Hobart TAS 7001, Australia, 2Wealth from Oceans Flagship, CSIRO Marine and recent changes in its physical marine environment. The impact on and temporal Atmospheric Research, GPO Box 1538, Hobart responses of the biota to change are less well understood, but appear to be due to TAS 7001, Australia, 3Tasmanian Aquaculture influences of climate, as well as the non-climate related past and continuing human and Fisheries Institute, Private Bag 49, Hobart impacts. We attempt to resolve the agents of change by examining major temporal TAS 7001, Australia 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 underwa- ter 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 extra- limital vagrants (4). Another 9 species, representing 7 families, experienced longer- term 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 Keywords and Atmospheric Research, GPO Box 1538, Hobart TAS 7001, Australia. Climate change, fishing, south-eastern Australia, spatial shift, Tasmania, E-mail: [email protected] temperate fishes, temporal shift. DOI: 10.1111/j.1466-8238.2010.00575.x 58 © 2010 Blackwell Publishing Ltd www.blackwellpublishing.com/geb Long-term shifts in a temperate fish fauna fauna has been described in a series of checklists and guides INTRODUCTION dating back to the late 1800s and early 1900s (e.g. Lord & Scott, Changes in faunal assemblages over time have been recorded in 1924). In the ‘1980s’, these fishes were surveyed extensively and many marine communities and are often linked to anthropo- good intra-regional information was obtained on the distribu- genic impacts, such as fishing (e.g. Jackson et al., 2001), pollu- tions of most species (e.g. Last et al., 1983). However, since the tion (e.g. Schiel et al., 2004), invasive species (e.g. Currie & mid-1990s many unusual records and sightings have been Parry, 1999) and climate change (e.g. Holbrook et al., 1997; reported, including coastal species not previously reported from Sagarin et al., 1999; Hiddink & Hofstede, 2008). Significant the region, poleward extensions of ‘1980s’ ranges, and increased changes in aquatic communities have been strongly associated local abundances in southern parts of Tasmania. with global warming, suggesting that these ecosystems are Stuart-Smith et al. (2009) concluded that Tasmanian subtidal extremely vulnerable to climate change (Richardson & reef communities have remained stable over the past decade Poloczanska, 2008). The effect of climate change on temperate despite evidence of localized ocean warming (Ridgway, 2007). inshore marine communities, specifically in rocky intertidal Nevertheless, they detected some species-level responses consid- zones, has been demonstrated in a number of studies (e.g. ered to be symptomatic of ocean warming, including southward Sagarin et al., 1999; Helmuth et al., 2006), with studies of the range extensions of some fishes. They suggested that major effects of climate on temperate fish communities in the North changes in faunal structure probably occurred in the decade Atlantic (e.g. Perry et al., 2005; Hiddink & Hofstede, 2008) and prior to commencement of their study; for example, forests of eastern (Holbrook et al., 1997) and south-west Pacific (Stuart- giant kelp (Macrocystis pyrifera) initially declined in the ‘1980s’ Smith et al., 2009). The Antipodean region is recognized as a (Edyvane, 2003). Hence, by examining shifts over a longer time ‘hotspot’ for ocean warming (Ridgway, 2007). Since 1944, the frame we should be able to gain better insights into the extent of East Australian Current (EAC) has extended poleward down the change. Stuart-Smith et al. (2009) also observed that less abun- coast of Tasmania by approximately 350 km and the sea surface dant species often exhibited greater shifts than the dominant temperature has warmed at an average rate of 2.28°C per elements of the fauna, presenting challenges when monitoring century (Ridgway, 2007; see also Fig. 1). Thus, biological climate impacts. responses to climate change in the region are expected to have Since 2006, when the senior author made an oral presentation already begun (Hobday et al., 2007; Ling et al., 2009). describing range changes in south-eastern Australian fishes, pat- The relatively species rich, cool temperate coastal ichthyo- terns of distributional shift in the fauna have become widely fauna of Tasmania is ideal for investigating temporal and spatial accepted (e.g. Hobday et al., 2007) but have not been rigorously shifts in species composition in this hotspot. The region is well- described. In addition, global warming may not be the only separated geographically from mainland Australia, but the driver of change in the region – changes in the fauna may have respective faunas are loosely interconnected through the Bass occurred due to exploitation. Resolving these agents of change is Strait by a series of island groups that potentially form ‘stepping important because not all distributional shifts are necessarily stones’ for the southward dispersal of adult fishes from northern climate related. Recolonization may occur in response to bioregions. Although complex, the biogeography of south- changes in fishing pressure, allowing a return of fishes from eastern Australia, which has been the subject of detailed inves- populations in less heavily exploited regions. Attribution of tigation for the purpose of regional marine planning (IMCRA, change is important for improving coastal management strate- 1996), is now reasonably well understood. The Tasmanian fish gies, 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 ich- thyofauna 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 repre- sented 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. Figure 1 The average annual sea surface temperature anomaly METHODS from the long-term average calculated from the HadlSST dataset (monthly, 1 °C; Rayner et al., (2003); http://hadobs.metoffice.com/ Data sources 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 The Tasmanian coastline is situated south of latitude 39°12′ Sin bars) over the period 1880–2009. 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 Allport), Johnston compiled the first annotated checklists of (Furneaux Group) and western (King Group) Bass Strait, and Tasmanian fishes. His work was thorough and comments on mainland Tasmania, including its adjacent islands (see Fig. 2). A occurrence and commonness were provided for most of the 188 temporal reconstruction of the coastal ichthyofauna was synthe-