Discriminating Stocks of Scomber australasicus Using a Holistic Approach: a Pilot Study
David W. Schmarr, Ian D. Whittington, Jennifer R. Ovenden, and Tim W. Ward
Abstract.—This study assesses the suitability of genetic approaches, parasitology and otolith microchemistry for determining the stock structure of spotted chub mackerel Scomber australasicus in Australasian waters and establishes protocols for using these techniques to determine variability within and among putative stocks. Seventy-five fish from three locations across the geographical distribution of S. australasicus in Australian waters (SE Queensland, South Australia and SE Western Australia) and one location in New Zealand were examined. Genetics and parasite assemblage were analyzed for all fish; otolith microchemistry of Australian fish was also examined. Techniques were successfully developed to extract and amplify a segment of the mtDNA control region, and results showed significant genetic heterogeneity among fish from Western Australia, Queensland, and New Zealand. Parasite analysis identified several taxa that are suitable for use as biological tags and enabled discrimination of fish collected from the four locations. Studies of otolith microchemistry using LA-ICP-MS had sufficient power to distinguish fish from the three Australian locations. This study suggests that there are multiple stocks of S. australasicus within Australian waters, proposes protocols for future studies of finer scale stock structure, and discusses the efficacy of each technique for stock discrimination.