Maturity and growth of sablefish, Anoplopoma fimbria, along the U.S. West Coast

Abstract

Life history parameters such as growth and reproductive processes are dynamic, and shift with environmental and anthropogenic influences. Providing up-to-date life history information is critical for population dynamic models that are used to manage fisheries. Sablefish, Anoplopoma fimbria, are a valuable groundfish species that support commercial fishing throughout the North Pacific Ocean, including off the U.S. West Coast. Ovaries were histologically assessed for maturity status, intensity of atresia, and the presence of post-ovulatory follicles. We evaluated coast-wide length and age at maturity for 477 female sablefish by fitting a logistic regression model to the proportion mature. We also examined length-at-age data for 525 female sablefish based on the von Bertalanffy growth model. Since maturity and growth are important components of models used to assess the status of sablefish, we explored variation in these life history parameters among three regions along the West Coast separated by major biogeographic features at Cape Mendocino, CA (40°26′N) and Pt. Conception, CA (34°27′N). Coast-wide estimates of length (L50) and age (A50) at 50% maturity were 54.64cm and 6.86 years, respectively. Differences in L50 were found north and south of Cape Mendocino, CA, and by depth (range 55–1280m). Length at 50% maturity decreased from north to south and with increasing depth within each region. Age at 50% maturity also differed north and south of Cape Mendocino, CA, with female sablefish maturing at a younger age further north. Growth of female sablefish demonstrated similar differences among geographic areas and by depth. Asymptotic size (L∞, cm) tended to increase at higher latitude and decrease with depth, while growth rates (k, year−1) were elevated north of Point Conception, CA, and generally at depths ≤550m. For female sablefish, the larger size and younger age at 50% maturity, as well as larger asymptotic sizes and somewhat elevated growth rates, were associated with regions within the California Current Ecosystem characterized by elevated productivity and cooler water temperature.