Microestructura de los otolitos Sagittae de larvas y juveniles de Merluccius hubbsi (Marini 1933): análisis comparativo entre las áreas de distribución bonaerense y norpatagónica
The life history of numerous aquatic organisms involves a pelagic larval stage, followed by a shift to a demersal or benthic existence (settlement) in the juvenile and adult stage. This transition and ecological, physiological and morphological changes frequently remain recorded like checks or marks in fish otoliths. As a contribution to the knowledge of hake (Merluccius hubbsi)life history, sagittae otoliths of larvae and juveniles with total length between 19 and 190 mm inhabiting North Patagonian and Bonaerensis waters in the Argentine sea (SW Atlantic)were analyzed. Using an image analysis system, otoliths microstructure was described and comparisons between left and right otoliths and between study areas in the following variables were realized: accesory growth centers number, higher primordium radius, higher otolith radius and settlement time (i.e. pelagic larval duration). Moreover, the otolith radius-fish total length relation to both areas was established and finally, macrostructural checks (in whole otoliths)was correlated with growth patterns observed on the otolith microstructure. Settlement time, approximately two months, was similar between areas. Furthermore no differences were found in the higher primordium radius. Two checks were identified prior to first annual ring. The first corresponds to a transition from juvenile stage and is coincident with settlement and takes place at 30 mm of total length. The second takes place at 60-80 mm of total length and 140-160 days of age. Differences as much in otolith radius and in the otolith radius-fish total length relation support the hypothesis that microstructure of hake otoliths is different between North Patagonian and Bonaerensis areas, specially in the juvenile stage.