Population estimation of bocaccio (Sebastes paucispinis) based on larval production

We estimate the stock size of bocaccio ( Sebastes paucispinis ) in the Southern California Bight based on the production of larvae. Area-weighted total length compositions of preflexion larvae in 2002 and 2003 were determined from ichthyoplankton survey data. Larval length-to-age transition matrices were estimated from data derived from the enumeration of daily otolith increments. In combination, these results were used to estimate daily rates of larval production and mortality during surveys conducted in those years. Daily rates of larval production were expanded to annual production rates using information developed from the long-term seasonal distribution of larvae in CalCOFI surveys. Total annual larval production was translated to total spawning biomass by calculation of the female population weight-specific fecundity derived from a length-based life table analysis of adult reproductive parameters. Our results indicate that there were 6953 – 10 656 metric tons of bocaccio biomass (males and females >16 cm fork length) in the Southern California Bight during the survey years, which agrees with biomass estimates from a traditional stock assessment. Unique and problematic aspects of the reproductive biology of Sebastes are discussed, including multiple spawning, weight-specific fecundity that depends on size, and bias in fecundity data gathered from vitellogenic ovaries.