Nutritional condition of Argentine anchovy Engraulis anchoita larvae in connection with nursery ground properties

Nutritional condition of anchovy Engraulis anchoita larvae from Northern Argentinean sea was assessed and compared in three areas characterized by dissimilar oceanographic features (estuarine, mixed and shelf waters). Morphometrical, histological and biochemical (RNA/DNA) indexes were used and larvae were compared through different developmental stages. Multivariate analyses performed on normalized morphometric variables showed that larvae from mixed waters where characterized by higher body depths; variables that indicate a better nutritional condition. Mean histological condition index obtained for larvae at intermediate developmental stages was significantly lower in estuarine waters than those estimated with samples from mixed or shelf waters. Anchovy larvae from the mixed water area showed a higher slope in the log RNA versus log DNA relationship than larvae from the other areas, which indicates that the former were in better condition. Also, standardized RNA/DNA index (RNA/DNAs) resulted slightly better in mixed waters than in shelf area, for larvae at intermediate developmental stages, but due to the high variability of RNA/DNA ratio, no significant differences were found between areas. Finally, using literature equations relating RNA/DNAs, temperature and growth, growth rate and growth performance were estimated. Mean growth performance did not differ between areas and was temperature independent. In conclusion, larval condition was relatively high at all stations, but our results suggested that it was slightly better in frontal areas characterized by water masses with intermediate salinities. We also provide evidence that anchovy larvae might not be food limited in any of the studied areas.

► We studied nutritional condition of Engraulis anchoita larvae from Northern Argentinean sea in three oceanographic areas: estuarine, mixed and shelf waters.
► Morphometrical, histological and biochemical (RNA/DNA) indexes were used and larvae were compared through different developmental stages.
► Larval condition was relatively high in the three areas, but our results suggested that it was slightly better in frontal areas characterized by water masses with intermediate salinities (mixed waters).
► We provide evidence that anchovy larvae might not be food limited in any of the studied areas.