Environmental associations of shortfin squid Illex argentinus (Cephalopoda: Ommastrephidae) in the Northern Patagonian Shelf

Abstract

We identified environmental associations (depth, bottom temperature and bottom salinity) of the shortfin squid Illex argentinus in the Northern Patagonian Shelf. Data are from 15 research bottom trawl surveys conducted in the Argentine–Uruguayan Common Fishing Zone (AUCFZ) between 1985 and 1998. Squid distribution in the surveyed area showed significant associations ( p < 0.05) mostly with depth and bottom temperature. Bathymetric associations of squid detected in March–April, May–June and July–August cruises revealed a preference of squid for deep depths (80–280 m, intermediate and external shelf) and cool bottom temperatures (4–10 °C, subantarctic water) within the survey area. In contrast, the results observed during November–December cruises showed a preference of squid for shallower depths (70–90 m) and warmer bottom temperatures. The majority of two-way environmental analyses showed significant associations, suggesting the existence of a strong correlation between the environmental factors used in our analyses. The identification of significant associations between squid distribution and bottom temperature seem to be related to the presence of strong thermal gradients within the study area. This could be supporting the existence of an association between I. argentinus with the Brazil–Malvinas confluence front and also with the shelf break front.