Variations in the measures of Argentine hake (Merluccius hubbsi) rings otoliths during their first-year: Evidence for stocks separation?

Measures of pelagic, demersal and first-year rings of otoliths belonging to two length groups of Argentine hake (Merluccius hubbsi) from the oceanic front of the de la Plata River (Argentine - Uruguayan Common Fishing Zone - AUCFZ) were analyzed. One group (individuals smaller than 25 cm) belonged to the nursery area of the northern sector (34 super( degree ) 30' -36 super( degree ) 00'S). The other group (individuals larger than 40 cm) belonged to the population that can migrate (northward and southward of the AUCFZ) and therefore could be found in most of the species distribution area. The variables which corresponded to the first length group (individuals smaller than 25 cm) presented higher mean values and less dispersion for each otolith ring measured (pelagic, demersal and first-year) than the second length group (individuals larger than 40 cm). These differences are significant (p