Statolith chemistry as a stock tag in the Argentine shortfin squid Illex argentinus

Abstract

With annual catches that have exceeded 1 million tons, the Argentine shortfin squid (Illex argentinus) is among the most important fisheries in the Southwest Atlantic Ocean. The objective of this study was to assess the statolith multi-elemental signature as a tool to delimit I. argentinus stocks on the Patagonian shelf and slope (Argentina) during summer 2019. Squids were caught from the Southpatagonic (SPS) and Summer Spawning (SSS) Stocks, and mixing area. Statolith multi-elemental signature (Ba/Ca, Li/Ca, Mg/Ca, Mn/Ca, Na/Ca, Pb/Ca, Sr/Ca, Zn/Ca) was determined by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Ba/Ca, Mg/Ca, Mn/Ca, Sr/Ca and Zn/Ca were significantly different between catch areas (p < 0.05). PERMANOVA (p < 0.05) and linear discriminant analysis (mean jackknifed classification= 70.6%), were effective for discriminating between the three sampling areas. The ratios that most contributed to the discrimination between groups were Zn/Ca, Pb/Ca, Mn/Ca, and Ba/Ca. Statolith chemical analyzes suggest that the SSS and SPS are segregated, although there is some degree of mixing between them, which supports previous inferences about population stock from other biological parameters. This study showed that the statolith microchemistry is a useful tool to study the population stock of I. argentinus.