Nicole M. Phillips

Biological and Genetic Characteristics of Restocked and Wild Acanthopagrus butcheri (Sparidae) in a Southwestern Australian Estuary

Acanthopagrus butcheri was restocked in an estuary in which it had become depleted. The restocked fish were cultured in 2001 and 2002 using broodstock from that estuary. These fish, whose otoliths had been stained with alizarin complexone, were released into the estuary and their biological performance tracked for seven to eight years. The 2002 cohort, introduced at circa four months old in autumn, survived far better than the 2001 cohort, introduced at circa seven months old in winter, when freshwater discharge peaks and temperatures are low. While restocked fish matured and grew nearly as fast as wild fish, the increase in density was accompanied by a reduced growth of wild fish. Genetic comparisons, using seven microsatellite loci, demonstrated that the expected heterozygosity and relatedness of restocked and wild A. butcheri, which is naturally characterized by low levels of genetic polymorphism, were similar. Although culturing did not demonstrably increase the level of inbreeding, it did result in the loss of some rare alleles. The biological and genetic results, together with the contribution of restocked A. butcheri to the commercial catch for this species in the estuary rising to 62–74% by 2007–2010, demonstrates the efficacy of using restocking to replenish depleted A. butcheri stocks.

Contrasting population structures of three Pristis sawfishes with different patterns of habitat use

This research demonstrates how population structure differs in elasmobranchs with different patterns of habitat use. Population structure was assessed using data at microsatellite loci in three species of Pristis sawfishes in northern Australian waters. Statistically significant population structure was found in each of P. clavata (FST = 0.021, F′ST = 0.151, P < 0.001) and P. zijsron (FST = 0.026, F′ST = 0.130, P < 0.001), which spend their entire life in marine waters. In contrast, there was no evidence of significant population structure in P. pristis, which uses freshwater rivers as juveniles and marine waters as adults (FST = 0.004, F′ST = 0.029, P = 0.210). When combined with the results of mtDNA analyses from a previous study, the results suggested that dispersal in P. pristis is male-biased, whereas both male and female gene flow are restricted at large spatial scales in each of P. clavata and P. zijsron in Australian waters. The present study has provided the first evidence of sex-biased dispersal in a sawfish.

Isolation and characterisation of novel microsatellite markers from Pagrus auratus and cross amplification in Acanthopagrus butcheri

We describe the isolation and characterisation of microsatellite loci for Pagrus auratus and cross amplification in another sparid, Acanthopagrus butcheri. Of 35 loci tested, 12 appear to be appropriate for population genetic studies of P. auratus, which are essential to inform management responses to evidence of overexploitation of this species. Three were ideal for A. butcheri and, when combined with published loci, can be used to assess the genetic implications of restocking depleted populations of this species.