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

Abstract

tThe spatial distribution of cephalopod paralarvae was studied in waters of San José Gulf (SJG), a shallowbasin connected to a larger gulf (San Matías, SMG) through a narrow mouth located on its northwest-ern margin. The gulf is characterized by a remarkable tidal circulation pattern providing contrastinghydrodynamic 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 aregular grid from October (mid spring) 2011 to March (late summer) 2012. Temperature-depth profilesshowed that while the western domain seawater column remains well mixed by tidal currents duringthe 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 latterwere found almost exclusively in the western domain whereas those from D. sanpaulensis were mainlysampled in the eastern domain. Low abundance of I. argentinus paralarvae in the eastern domain suggeststhat buoyant egg masses of this squid are not released in SJG; instead they, or the hatching paralarvaeemerging from them, could be sequentially advected from and expelled to SMG by tidal currents. Onthe other hand, the spatial distribution of D. sanpaulensis paralarvae suggests that those hatching on theshallow marginal bottoms of the eastern domain are retained in this region while those hatching at thewestern domain are flushed out to SMG by tidal currents.