Variability of egg escapement, fishing mortality and spawning population in the market squid fishery in the California Current Ecosystem

With an average yield of 70 000 Mt from 1999 to 2006, market squid (Doryteuthis opalescens) represents one of the most commercially valuable and biologically productive populations off California. An egg escapement model was developed for evaluating the population's reproductive response to varying levels of fishing pressure and, potentially, for aiding management of the fishery. The model is founded on eggs-per-recruit theory, assuming catch fecundity is related to daily-based fishing mortality (F), i.e. analysis generated estimates of proportional egg escapement, S(F), as a function of F per quarter from 1999 to 2006 in three spawning grounds off northern and southern California. Fishing pressure was generally high, with mean derived F ranging from 0.20 to 6 per day. Mean estimated S(F) ranged from 0.08 to 0.75, but in most quarters was higher than 0.30. The classical model was extended for estimating absolute abundance of the resource based on F. Market squid were more abundant in southern California, where mean spawning stock peaked at 1.50 x 10(9) females, similar to 108 000 and 130 000 Mt in autumn 2000 and winter 2005 respectively. Although time demanding, this per-recruit analysis represents an effective approach for monitoring reproductive outputs and for aiding stock status determinations of harvested market squid.