The Chilean hake (Merluccius gayi gayi) is the predominant groundfish
species inhabiting the southern Humboldt, mainly from Coquimbo (29° S) to Puerto Montt
(42° S). At present there is only limited knowledge on the spatial distribution of
juveniles of this species, particularly concerning its dependence on key physical
characteristics. On the basis of annual surveys carried out during austral winters from
1997 to 2006, changes in the presence of juveniles were studied using Generalized Additive
Model techniques. Temporal factors and spatial effects were more important than single
physical variables in explaining the presence of juvenile hake (<34 cm total
length). Juvenile hake had a preference for shallower waters. Although salinity and oxygen
were significant, their contribution was marginal. Juvenile hake seem to prefer shallow
oxygenated waters, but the nonlinear relationships and partial secondary peaks detected in
salinity and oxygen probably only reflected the influence of three water masses found in
the winter habitat. Endogenous factors could be more important in determining temporal and
spatial changes in the proportion of juvenile hake. An important change in the presence of
juveniles has occurred since 2004, coinciding with a significant decline in biomass of
adult hake. It is postulated that cannibalism pressure from adults has probably declined
and that spatial and temporal changes in the presence of juvenile hake seem to be more
associated with fishery-induced demographic effects.