科研之友
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摘要
The Chilean hake (Merluccius gayi gayi) is the predominant groundfish species inhabiting the southern Humboldt, mainly from Coquimbo (29 degrees S) to Puerto Montt (42 degrees 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.
- 出版日期2011-4
