Utility of a Collaborative At‐Sea Sampling Program (CASP) for the California Spiny Lobster Commercial Fishery: Catch Characteristics and Implications for Management

Fisheries management, including the development of fishery management plans (FMPs), requires the best available scientific information. To address this need, we piloted a collaborative at‐sea sampling program (CASP) among California commercial lobster fishermen, scientists, and fishery managers to develop scientifically rigorous protocols and collect, analyze, and interpret essential fisheries information (EFI). Significant differences in catch characteristics among three regions (South, North Coast, and Northwest Islands) were documented. Legal CPUE was generally similar among regions, whereas sublegal CPUE was consistently highest in the South, followed by the North Coast and Northwest Islands. Evaluation of size structure revealed that legal lobsters were significantly smaller, just larger than legal size, in the South than in the other two regions, suggesting a higher exploitation rate there. Despite this, the South had significantly more prerecruits than the northern regions, a fact not considered in present fishery models. We also found a female bias in the legal sex ratios in the north regions and in the sublegal sex ratios in all regions that could affect model parameters for trap vulnerability and reproductive capacity. A discrepancy in the average weight of legal lobster for the Northwest Islands was identified which has implications for the spawning potential ratio, a reference point that elicits management action. The regional variations in catch characteristics suggest that the California lobster fishery would benefit from using more sophisticated models that incorporate area‐based EFI to better inform the harvest control rules. This finding supports the recommendations of the lobster FMP scientific review panel and the interests of resource managers, with the CASP data illustrating the value of the additional EFI and a mechanism for obtaining it. The demonstrated utility of the CASP for both cross‐checking and providing additional data supports its ongoing use to inform management of the lobster fishery and as a model for other fisheries.