Microsatellite-based assessment of the genetic structure of snapper, Chrysophrys auratus, in Australasia

The patterns of variation at 12 microsatellite loci are used to determine whether Snapper, Chrysophrys auratus, is genetically homogeneous across its range in Western Australian waters and to elucidate the extent to which the genetic composition of this exploited sparid varies among regions in Australasia. Chrysophrys auratus was collected from seven locations in Western Australia (WA), southwards from Carnarvon (25°05–15′S, 113°25–35′E) on the mid-west coast and eastwards to Esperance (34°30′S, 122°10′E) on the south coast. The levels of genetic differentiation among samples extending 1350 km from Carnarvon to Albany (35°20′S, 117°50′E) on the south coast, but not to Esperance ∼ 410 km further east, were low and non-significant (e.g. DEST = 0.003; P = 0.167). This implies that C. auratus is genetically homogeneous along the majority of its extensive range in WA. It is proposed that this reflects wide-spread dispersal of the early life stages (ELS), facilitated by the southward-flowing Leeuwin current and northward-flowing, wind-driven inshore currents, supplemented by movements of juveniles and adults. The genetic composition of the sample of C. auratus from Gulf St Vincent on the south coast (central) of Australia (34°50′S, 138°10′E) was similar to those from Albany and Esperance on the south coast (west) but typically distinct from those from the south coast (east), west and east coasts of Australia. This genetic structure is presumably related to how the eastwards-flowing Leeuwin current and/or the westwards-flowing Flinders currents disperse ELS. Microsatellite data imply that C. auratus from the Port Phillip Bay on the south coast (east), Sydney on the east coast and from Hauraki Gulf in New Zealand each represent distinct genetic stocks. The genetic composition of C. auratus from the Port Phillip Bay is particularly distinct, indicating that this population is relatively isolated and thus potentially more susceptible to exploitation. The results of the present and other studies indicate, however, that gene flow in C. auratus is typically sufficient to maintain genetic homogeneity over 100s of kilometres, as occurs in Western Australia. Thus, C. auratus spawned in one area can potentially act as a source of recruits for other areas and thereby ameliorate the impacts of fishing.