Intra-annual growth variations of young-of-the-year hake (merluccius hubbsi) of the uruguayan continental shelf based on otolith anlysis

摘要

The growth of young-of-the-year hake (merluccius hubbsi) (<25 cm TL) and its intra-annual variations are analyzed. A total of 307 individuals was collected in the Uruguayan continental shelf, covering the four seasons of the year. pelagic, demersal and first-year ring otolith measurements and otolith border type characteristics are taken into account. The growth that occurred between he time of hatching and the first-year was different for individuals collected in different seasons. Summer season was found to have the smallest averages (p<0.05) for pelagic, demersal and first-year rings. Different spawning times and variability in the environmental features throughout the year could affect the growth characteristics of M.hubbsi juveniles. Juveniles form autumn to winter spawning would mark their first-year in the following witer and would take longer to get to each of the analyzed rings. Howerver, juveniles from spring spawning also mark the first-year in the following witer but, would show shorter life periods related to otolith and rings develpments. The demersal ring formation showed significant differences between autumn and spring. This ring indicated the change between pelagic and demersal habitat. The temporal variation in the upper mixed layer and thermocline development throughout he year could be the cause of differences in growth development and behavior. Our current understanding of mesoscale physical processes sugtgests that these changes associaed with biological interactions may play an important role in juvenile rcruitment. Further investigations of mesoscale physical processes are needed to confirm these hypotheses.