Intra-annual growth variations of young-of-the-year hake (Merluccius hubbsi) of the Uruguayan continental shelf based on otolith analysis

The growth of young-of-the year hake (Merluccius hubbsi) (<25 cm TL) and it s intra-annual variations are analyzed. A total of 307 individuals was coll ected in the Uruguayan continental shelf, covering the four seasons of the year. Pelagic, demersal and first-year ring otolith measurements and otolit h border type characteristics are taken into account. The growth that occur red between the time of hatching and the first-year was different for indiv iduals collected in different seasons. Summer season was found to have the smallest averages (p < 0.05) for pelagic, demersal and first-year rings. Di fferent spawning times and variability in the environmental features throug hout the year could affect the growth characteristics of M. hubbsi juvenile s. Juveniles from autumn to winter spawning would mark their first-year in the following winter and would take longer to get to each of the analyzed r ings. However, juveniles from spring spawning also mark the first-year in t he following winter but, would show shorter life periods related to otolith and rings developments. The demersal ring formation showed significant dif ferences between autumn and spring. This ring indicated the change between pelagic and demersal habitat. The temporal variation in the upper mixed lay er and thermocline development throughout the year could be the cause of di fferences in growth development and behavior. Our current understanding of mesoscale physical processes suggests that these changes associated with bi ological interactions may play an important role in juvenile recruitment. F urther investigations of mesoscale physical processes are needed to confirm these hypotheses. (C) 1999 Elsevier Science B.V. All rights reserved.