Occurrence of tropical fishes in temperate southeastern Australia: Role of the East Australian Current D.J. Booth, W.F. Figueira * , M.A. Gregson, L. Brown, G. Beretta Department of Environmental Sciences, University of Technology, Sydney, P.O. Box 123, Broadway, NSW 2007, Australia Received 5 September 2005; accepted 6 October 2006 Available online 28 November 2006 Abstract Dispersal of larval propagules is the major mechanism facilitating connectivity of marine populations. However, only a fraction of larvae settle in suitable habitat. For coral reef fishes, many larvae are advected away from coral reefs, often despite strong behavioural mechanisms (including swimming), and some may travel long distances away from the tropics. Here we document the occurrence of tropical reef fishes along the southeast coast of Australia between 2003 and 2005 and evaluate the role of the East Australian Current (EAC) in driving this pattern. In total we observed 47 species of tropical fishes from 11 families during the summer recruitment season (January to May) at locations spanning most of the length of the New South Wales coast (28  Se37.5  S latitude, w1700 km from the southern end of the Great Barrier Reef). Southern locations tended to have reduced richness and density relative to northern ones. In general, the southward extent of distribution of the most commonly observed species was well explained by their planktonic larval durations. Recruitment events tended to be much more episodic in Merimbula (37  S) than Sydney (34  S), but there was little evidence for interannual similarity in the spatial patterns of recruitment of individual species with exception of the numerical dominance of Abudefduf vaigiensis and Abudefduf sexfasciatus (Pomacentridae) at the Sydney location and of Chaetodon auriga and Chaetodon flavirostris (Chaetodontidae) at the Merimbula location. Despite strong evidence for the role of the EAC in the transport of these species at a coastal scale, we found little evidence that individual recruitment events were correlated with local increases in water temperature that would be associated with EAC ingress. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: butterflyfish; East Australian Current; damselfish; marine; transport processes; tropical fish; Australia; New South Wales; regional boundaries [29  Se38  S, 149  Ee155  E] 1. Introduction The production of pelagic larvae is a nearly ubiquitous fea- ture of the life history of marine fish (Leis, 1991). While recent work has demonstrated the often substantial sensory (Leis et al., 2002; Leis and Carson-Ewart, 2003) and locomo- tory abilities (Stobutzki and Bellwood, 1997; Bellwood and Fisher, 2001) of larvae of several species of fish, these abilities are most pronounced near the end of the pelagic larval phase (Fisher et al., 2000) and thus there will be some portion of this phase during which the larvae are subject to the vagaries of ocean currents. The potential for long distance transport in ocean currents during this period is tremendous (Roberts, 1997). Particularly apparent is the expatriation (removal from ‘‘typical’’ biogeographic range; Hare and Cowen, 1991) of tropical fish larvae into temperate waters by means of poleward-flowing boundary currents. Tropical fish have been consistently observed since at least 1964 along the east coast of Japan as far north as Tsuyazaki (northern coast of Kyushu Island, 33  47 0 N latitude, Nakazono, 2002). Along the east coast of North America the seasonal (summer) arrival of tropical fish has been documented as far north as Long Island, New York (40  N latitude, McBride, 1996; McBride and Able, 1998). The powerful Gulf Stream is the primary mechanism by which these larvae are moved from the sub- tropical reefs of the South Atlantic Bight into the temperate regions of the mid-Atlantic Bight (Grothues et al., 2002). * Corresponding author. E-mail address: william.figueira@uts.edu.au (W.F. Figueira). 0272-7714/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.ecss.2006.10.003 Estuarine, Coastal and Shelf Science 72 (2007) 102e114 www.elsevier.com/locate/ecss