Thesis

Age, growth and genetic diversity of giant sea bass, Stereolepis gigas

The giant sea bass, Stereolepis gigas, is a large predatory fish that inhabits the southern California kelp forest community. S. gigas is a critically endangered species, yet little is known about its life history. A more complete knowledge of the life history of this once commercially viable fish is necessary before an effective management strategy can be proposed. Giant sea bass were collected through collaborative efforts with commercial fish landings, scientific gill-netting, and through catch-and-release methods employed by recreational fisherman. A total of 59 samples were used for both mitochondrial DNA and age-and-growth analysis. Genetic analysis of the mitochondrial control region indicated gene flow among all sampling sites, no phylogeographic structure, as well as low haplotype (h) and nucleotide diversity (π). Sagittal otoliths were cross sectioned and analyzed with digital microscopy techniques, resulting in the verification that S. gigas is a long-lived species growing to at least 76 years of age. The calculated von Bertalanffy growth function (lt= 2048.4(1-e -0.041(t+0.839)) for S. gigas was also characteristic of a slow growing, apex predator. Long-lived species that are slow to reach maturity often have a low resilience to over-fishing, therefore it is of paramount importance that we continue to collect essential life history data on this species in order to more effectively protect and manage the S. gigas population.

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