The effect of physical and biological variables upon condition of Merluccius hubbsi (age-0+) of the northern stock (argentine shelf, SW Atlantic Ocean)

Abstract

Argentine hake Merluccius hubbsi is one of the most important fishery resources in the Argentinean Continental Shelf (ACS; SW Atlantic Ocean). In the last decades, the Northern stock (34°30′-41°S) has supported a drastic biomass decreasing due to overexploitation. Since the strength of a year class is highly influenced by the survival of age-0+ individuals, studies on their nutritional condition are essential. Age-0+ northern hake nurse in a highly complex oceanographic and ecological system, where environmentally-driven changes upon their physiological status are expected. Hence, several condition (relative condition factor, hepatosomatic index, liver lipid content) and feeding (prey intake) indices were combined with physical (temperature, salinity) and biological (chlorophyll-a concentration, prey abundance) variables to determine spatial variations in age-0+ hake nutritional status. Better conditioned individuals inhabited areas of the study region where chlorophyll-a concentration and zooplanktonic prey abundance exhibited their maximum. A bottom-up control of age-0+ hake physiological status is suggested, mediated by the consumption of the herbivorous euphausiid Euphausia lucens, which was the preferred prey. These lipid-rich prey would be beneficial with respect to other available options in the environment, such as hyperid amphipods. Results complement previous observations upon individuals of the Patagonian stock, and provide a thorough insight into age-0+ Northern hake nutritional status, significantly contributing to M. hubbsi recruitment studies and management in the ACS.