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.

Pacific Sardine Sardinops sagax and Northern Anchovy Engraulis mordax are commercially important West Coast fish stocks managed within the Coastal Pelagic Species (CPS) complex by the Pacific Fishery Management Council and National Marine Fisheries Service. Before 2020, survey indices used in Pacific Sardine stock assessments did not explicitly account for nearshore biomass, which presumably had been relatively small compared to the total biomass of the population, but since 2015, has been a more substantial component of total biomass. During the recent Pacific Sardine stock decline, the California Department of Fish and Wildlife and the California Wetfish Producers Association collaborated on an aerial survey off California to estimate nearshore (within 3,600 m from shore) CPS biomass to inform assessments. This project has also involved federal fisheries biologists and Pacific Fishery Management Council advisory bodies and committees, representing a unique collaborative effort to improve data used in CPS fisheries management. We will discuss successes, issues, and challenges in implementing this nontraditional survey and how these data can continue to inform future stock assessments.

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