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“The effects of temperature on poikilothermic organisms are felt at every level of biological organization, from animal behavior and physiology to the cellular expression of genes and proteins (Huey buy Pexidartinib & Bennet, 1990). For tropical estuarine species such as barramundi (Lates calcarifer), coping with fluctuations

in environmental temperature is paramount to their survival as estuarine water temperatures vary significantly on a daily and seasonal basis. Climate change is expected to further exacerbate these already frequent variations in environmental conditions, and is thus likely to pose a significant challenge for local barramundi populations in the near future (Bianchi, 2006). Australian populations of barramundi (L. calcarifer) range from

the Ashburton River (22° 30′ S) in Western Australia, across the tropical north of the country, and down the eastern Queensland coast to the Noosa River (26° 30′ S). Throughout this distribution barramundi inhabit fresh, estuarine and near coastal waters over some 16° of latitude find protocol that encompass a wide range of environmental temperatures. At the northern and southern end of their Australian distribution, mean yearly average temperatures differ significantly and range from 23.2–32 °C in Darwin, Northern Territory, to 18.5–27.7 °C in Gladstone, central Queensland, respectively (Bureau of Meteorology, http://www.bom.gov.au). As a species, barramundi experience significantly warmer and more consistent temperatures at lower latitudes while encountering cooler and less consistent temperatures at higher latitudes. Across this thermal cline barramundi has also been shown to exhibit significant genetic structuring, with Niclosamide up to 16 discrete genetic stocks identified to date ( Keenan, 1994 and Salini and Shaklee, 1988) ( Fig. 1). In addition to this, barramundi are euryhaline and

catadromous species and require estuarine and in-shore marine habitats to breed. However, after eggs hatch, juvenile barramundi migrate upstream to freshwater river systems away from river mouths ( Pusey et al., 2004) and on the basis of recorded tagged fish movements it is believed that the migration of individuals between adjacent river-mouths more than 100 km apart, while possible, is a relatively rare event ( Keenan, 1994). Therefore, gene flow amongst adjacent populations appears to be restricted, leading to the patterns of genetic structure exhibited in this species. Taken together, these observations have prompted speculation as to whether the high levels of genetic structure within populations of barramundi have translated into functional genetic adaptation to local environmental stressors, for example temperature. Examination of the current barramundi stock structure in Australia through biogeographical studies suggests that phenotypic differences arising between populations from genetic differences should be relatively small.