Identification of western South Atlantic stocks of the Lane snapper (Lutjanus synagris) from an otolith based multi-proxy approach

Accurate stock assessments are the basis of adequate fisheries management. In the Southwest Atlantic, fisheries of the Lane snapper (Lutjanus synagris) have been growing in importance in the last decades, following declines in other snapper fisheries since the late 1970 s, with evidence of overexploitation accumulating since the mid-2000 s. Contrasting environmental conditions along the area are potential drivers of stock separation, yet no phenotypic approach has ever been applied to the stock identification of the species in the area. Here we employ a multi-proxy approach based on otolith shape and isotopic composition to identify Lane snapper stocks in the Southwest Atlantic, and also investigate whether geographical limits of Large Marine Ecosystems and Marine Ecoregions are suitable surrogates for estimating stock boundaries, which could be useful for application in stock assessments when stock boundaries are unknown. The spatial heterogeneity evidenced by all proxies used supported the existence of distinct Lane snapper stocks, contrasting to previous genetic-based studies. Our results reveal a strong influence of environmental and oceanographic conditions as drivers of stock separation. The Marine Ecoregions system was considered a more appropriate surrogate for delineating stock boundaries, representing a fast and feasible approach to facilitate stock assessments in other data-limited fisheries. •First use of a phenotypic approach to identify Lane snapper stocks in the SWA.•Evidence of stock separation contrasts to previous genetic-based results.•Contrasting environmental conditions suggested as main drivers of stock separation.•Marine Ecoregions are appropriate surrogates for delineating stock boundaries.•Use of a multi-proxy approach was an efficient tool to detect stock structure.