ROLE OF OCEANOGRAPHIC AND TOPOGRAPHIC FACTORS IN THE RETENTION OF HAKE (MERLUCCIUS-GAYI GAYI GUICHENOT, 1848) LARVAE IN THE UPWELLING SYSTEM OFF CENTRAL-SOUTHERN CHILE

At present there is limited information available on the ecology of th e hake (Merluccius gayi gayi Guichenot, 1848) in the spawning zone off central-southern Chile. The existing information indicates highly com plex topography of the area (e.g. canyons and wide terraces) and ocean ographic characteristics (e.g. upwelling processes and associated eddi es). This suggests that the coastal dynamics of this zone influence th e spatial distribution of hake larvae and could act as a mechanism for larval retention. Ichthyoplankton samples (Bongo net 500 mu m) were c ollected between September 10(th) and 12(th), 1991. Hydrographic infor mation (temperature, salinity and density) was recorded at 38 stations distributed along 6 transects running perpendicular to the coast, bet ween the outlet of Itata River (36 degrees 22' S) and Lavapie Point (3 7 degrees 10' S). Twenty fish larvae species were identified, M. gayi gayi being the numerical dominant (> 70%). For this species, the eggs showed the highest concentration associated at a northwest sector, fin ding an important spawn nucleus on the Itata Terrace. Our results sugg ests that the study area represents an important spawning zone for M. gayi gayi which is spatially different to that off Valparaiso and San Antonio. A significant shifting in the size-frequency distribution of M. gayi gayi larvae (toward high sizes in the range of 4 to 8 mm SL) f rom oceanic to coastal waters and from the north to the south suggest that: oceanographic processes may play an important: role in the larva l transport. The existence of a possible recirculation mechanism that could favour larval retention on the continental shelf is discussed.