Distribución estacional y estructura poblacional del bacalao austral (Pisces, Moridae, Salilota australis) en la zona económica exclusiva argentina entre los 45°S y 56°S durante 1992 y 1993

Abstract

The Patagonian cod (Salilota australis) inhabits the SW Atlantic from 38°S up to 55°S, as well as the Pacific Ocean from 40°S up to 57°S. The annual catches of this species by both the Argentine fleet and those operating around the Malvinas Islands have significantly increased during the decade 1990-2000, peaking to 16,556 t in 1996. After this, a marked decrease in landings was noticed, and during 2003 the catch was 7,924 t. Seasonal distribution, concentration grounds, and population structure of the Patagonian cod from the Argentine Sea are described, and the mean densities of the species are seasonally related to latitude, temperature and depth, on the basis of data from surveys carried out by the INIDEP research vessels in 1992 and 1993. Highest mean densities showed to move from spring to winter according to both latitudes (southwards) and depth (towards deeper waters). No sea bottom temperature (SBT) data corresponding to fall were available, but it was clear that main concentrations of cod during the other seasons were related to SBT of 5 °C, and a little more tolerance was found during the summer. Within the studied area, mainly adult fish were caught (> 72%), and the most frequent sizes were recorded into the range of 38-54 cm total length. Sex ratio was close to 1:1 almost all over the year, except during the fall, when males represented 61%. Near mature juveniles (sized 27-38 cm) were present throughout the year, and percentages in the samples were highest at 55°S lat. during winter. Juveniles close to be one year old (14-17 cm) were found during the winter season, at 55°S lat. and 166 m depth.