Northern Patagonian gulfs (Argentina) as spawning grounds of squids

AUGUSTO CÉSAR CRESPI ABRIL

Oldenburg

Congreso; Youmares 4; 2013

The spatial distribution of squid paralarvae was studied in waters of San José (SJG) and San Matias gulfs (SMG). SJG is a shallow basin opening to SMG through a narrow mouth located at its northwestern margin, characterized by a remarkable tidal circulation pattern providing contrasting hydrodynamic conditions on its western and eastern domains. During each tidal cycle, SJG ejects 15% of its total volume of water to SMG. This causes that water jets of SJG influence the southern part of SMG. Zooplankton tows (105 in total) and depth-temperature profiling (70 in total) were conducted on a monthly basis at fixed stations forming a regular grid in SJG from October (mid spring) 2011 to March (late summer) 2012. IN SMG, a total of 28 zooplankton net tows were conducted in a regular grid in November 2009 and temperature profiles were conducted in each station. In SJG, temperature-depth profiles showed that while the western domain seawater column stays well mixed by tidal currents during the whole period, stratification develops from November to March at the eastern domain. Positive zooplankton tows were for paralarvae of Doryteuthis sanpaulensis and Illex argentinus. The last were found almost exclusively in the western domain and those from D. sanpaulensis were mainly sampled in the eastern domain. Low abundance of I. argentinus paralarvae in the eastern domain suggests that buoyant egg masses of this squid are not released in SJG; instead they, or the hatching paralarvae emerging from them, could be sequentially advected from and expelled to SMG by tidal currents. On the other hand, the spatial distribution of paralarvae from D. sanpaulensis suggests that those hatching on the shallow marginal bottoms of the eastern domain are retained in this region while those hatching at the western domain are flushed out to SMG by tidal currents.