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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 × 109 females, ~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.

Whether fluctuation in density influenced the growth and maturation variables of three aggregated cohorts (fish born during the 1986-1993, 1996-2003 and 2004-2008 periods) of Pacific sardine Sardinops sagax caeruleus collected off the Californian coast from 2004 to 2010 was investigated. Using a von Bertalanffy mixed-effects model with aggregated cohorts as covariates, estimated growth rate significantly covaried with aggregated cohorts. Growth rate (K) was modelled as a fixed effect and estimated to be 0.264 ± 0.015 (±s.e). Statistical contrasts among aggregated cohorts showed that the 1996-2003 cohorts had a significantly lower growth rate than the other two aggregated cohorts. The theoretical age at length zero (t0) and the standard length at infinity (L(S∞)) were modelled as random effects, and were estimated to be -2.885 ± 0.259 (±s.e) and 273.13 ± 6.533 mm (±s.e). The relation of ovary-free mass at length was significantly different among the three aggregated cohorts, with the allometric coefficient estimated to be 2.850 ± 0.013 (±s.e) for the S. sagax population. The age-at-length trajectory of S. sagax born between 1986 and 2008 showed strong density dependence effects on somatic growth rates. In contrast to the density-dependent nature of growth, the probability to be mature at-size or at-age was not significantly affected by aggregated cohort density. The size and the age-at-50% maturity were estimated to be 150.92 mm and 0.56 years, respectively. Stock migration, natural fluctuations in biomass and removal of older and larger S. sagax by fishing might have been interplaying factors controlling growth parameters during 1986-2010.

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