Spatial distribution of cephalopod paralarvae in San Jose Gulf (Northern Patagonia, Argentina): The role of tidal circulation in larval dispersal

摘要

The spatial distribution of cephalopod paralarvae was studied in waters of San Jose Gulf (SJG), a shallow basin connected to a larger gulf (San Matias, SMG) through a narrow mouth located on its northwestern margin. The gulf is characterized by a remarkable tidal circulation pattern providing contrasting hydrodynamic conditions between the western and eastern domains. Zooplankton net tows (n = 104) and depth-temperature profiling (n = 70) were conducted on a monthly basis at fixed stations forming a regular grid from October (mid spring) 2011 to March (late summer) 2012. Temperature-depth profiles showed that while the western domain seawater column remains well mixed by tidal currents during the whole period, stratification develops from November to March on the eastern domain. Positive zoo-plankton net tows were sporadic for early-life stages of Semirossia tenera (n = 1) and Robsonella fontaniana (n = 3), and more frequent for those of Doryteuthis sanpaulensis (n = 9) and Illex argentinus (n = 9). The latter were found almost exclusively in the western domain whereas 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 D. sanpaulensis paralarvae 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. (C) 2013 Elsevier B.V. All rights reserved.CT 1st Triennial International Symposium of the Cephalopod-International-Advisory-Council (CIAC)CY OCT 29-NOV 02, 2012CL Florianopolis, BRAZILSP Cephalopod Int Advisory Council