Seasonal and spatial variability in condition of age-0+Argentine hakeMerluccius hubbsiMarini, 1933, in the San Jorge Gulf (Argentina): A bottom-up perspective

摘要

In the north Patagonian region of the Argentinean Continental Shelf, the San Jorge Gulf (SJG; 45 degrees-47 degrees S, 65 degrees 30MODIFIER LETTER PRIME-67 degrees 30MODIFIER LETTER PRIMEW) is the main nursery ground of age-0+ Argentine hakeMerluccius hubbsiMarini, 1933, one of the most important fishery resources in Argentina. The gulf exhibits strong seasonal and spatial fluctuations in environmental features, which might affect survival of age-0+ individuals and recruitment to the adult population. Our main goal was to evaluate the seasonal and spatial dynamics of their nutritional status within the SJG in winter 2016, spring 2016 and summer 2017. Condition indices (relative condition factorK(n), hepatosomatic index HSI and liver lipid content %L) and diet information (feeding incidence and relative importance of prey) were combined with physical (temperature and salinity) and biological (satellite chlorophyll-aconcentration; chl-a) data. Age-0+ condition indices and prey intake showed significant seasonal variations, with minimum values in winter, intermediate in summer and maximum in spring, strongly coupled to the mean chl-aconcentration in each season. Herbivorous euphausiidsEuphausiaspp. were the preferred prey along the study period. A bottom-up effect on condition of age-0+ hake is suggested, manifested as lower condition values in winter, the less productive season. Spatially, better conditioned individuals matched sectors of the gulf where chl-aconcentrations were higher, coupled to the presence of frontal systems. Monitoring age-0+ hake nutritional status is relevant in the current global change scenario, which might modify phytoplankton biomass and composition and, consequently, the herbivorous zooplankton abundances.