Maturity and growth of darkblotched rockfish, Sebastes crameri, along the U.S. west coast

Abstract

Changes in the reproductive biology of fish stocks over time can affect the accuracy of recruitment estimates used by fisheries managers to determine harvest levels. For heavily depleted species, shifts in parameters such as age and size at maturity may occur over a relatively short time period in response to changes in selective pressure or population density. We examined the reproductive biology of darkblotched rockfish (Sebastes crameri), a commercially and ecologically important groundfish in the California Current ecosystem along the west coast of North America. The National Marine Fisheries Service currently lists darkblotched rockfish as “rebuilding” after years of intense overfishing in the 1980s and 1990s. We examined ovaries and age structures collected in 2011 and 2012 for oocyte development stage and maturity. Length and age at 50 % maturity were estimated as 30.0 cm fork length and 6.0 years, respectively, indicating a 12 and 29 % decrease compared to the length and age at 50 % maturity previously reported for this stock based on specimens collected from 1986 to 1987. This reduction increased the estimate of spawning stock biomass in a recent darkblotched rockfish stock assessment. Our study also revealed spatial patterns in darkblotched rockfish maturity along the U.S. west coast, including a notable decrease in the proportion of mature fish encountered south of central Oregon. Our findings demonstrate the importance of periodically updating life history data used in stock assessment models, and also highlight the potential value of spatial management toward sustainable fishing of rockfish species.