A data-limited approach to determine the status of the artisanal fishery of sea silverside in southern Chile

Abstract

Artisanal fisheries are essential, but for most the status of the stock supporting the fishing activity remains unknown due to lack of data and difficult access to sampling. For example, the artisanal fishery of sea silverside Odontesthes (Austromenidia) regia, in the Los Lagos administrative region of Chile, requires a data-limited approach to determine its status because the fishery administration has not invested in its monitoring. The approach consisted of estimating the spawning potential ratio (SPR) from length-frequency data collected in 2019 using length-based spawning potential ratio (LBSPR) and biological reference points using the only-catch optimized method (OCOM) to catch data covering from 1960 to 2020. In addition, five age-structured sea silverside populations were simulated considering uncertainty in recruitment and utilizing life-history parameters estimated by FishLife. According to LBSPR, the SPR was 0.58 (95% confidence intervals: 0.5-0.7), suggesting a fully exploited fishery status. The OCOM result was inconsistent with the life-history parameters and was discarded as a valid sea silverside stock assessment. The age-structured population simulations indicated evidence of a reduction in the spawning stock biomass close to 75% of the unexploited condition in 1960. Thus, the underexploited status reached a probability close to 49.4%, and the fully exploited status was 41.2%. The framework for a data-limited stock-assessment approach and results obtained here for the sea silverside are starting essential steps that may be emulated in other artisanal data-limited fisheries.