White seabass (Atractoscion nobilis ) is a commercially and recreationally important Sciaenid species off the coast of California, with fisheries dating back over a hundred years. Beginning in the 1920s-1930s, periods of population decline have been noted in this species, prompting the establishment of management plans. In addition to harvest regulation changes to combat declining stocks, the California state legislature established the Ocean Resources Enhancement and Hatchery Program to aid in the conservation of white seabass through stocking of cultured juveniles in southern California. Aquaculture-based stock enhancement is a powerful tool to promote conservation and increase population abundance of stocks of marine species.
Figure 1. Archived white seabass otoliths which range from the Channel Islands, USA to Baja California, Mexico.
White seabass have been released by Hubbs-SeaWorld Research Institute since the 1980s, with almost 2.7 million juveniles released to date. Although assessments of population structure have been conducted, a fine-scale assessment of genetic health, genetic diversity, and contribution to the wild population is lacking for this species. Our project has developed a highly polymorphic microsatellite marker panel for white seabass which is able to differentiate individuals with a high level of confidence. Using this, biological samples from fin clips and otoliths of over 400 adult white seabass broodstock used in the stocking programs (dating back to 1995) have been genotyped. The resulting genetic data were subsequently used to develop a genetic parentage model in a likelihood-based program (Cervus) to determine the contribution of stocked fish. Following genotyping of samples of unknown parentage, the model provides genetic assignment of the most likely candidate hatchery parents if a stocked fish. A rchived white seabass otoliths (>1400) from field collections spanning 1992-2019 (Figure 1) have been genotyped to evaluate comparisons of traditional coded wire tag and genetic-based tagging methods and assess the contribution of cultured white seabass to the wild sub-adult and adult population. The combined dataset will provide the opportunity to characterize fine-scale patterns of gene flow and genetic health of the wild population(s). T o responsibly conduct a stocking program which prioritizes the maintenance of diversity in the wild population, a genetic component is a powerful tracking tool to evaluate contribution to the population and provide critical information to minimize any potential negative impacts to the wild population.