A regional comparison of nutritional condition of SW Atlantic anchovy larvae, Engraulis anchoita, based on RNA/DNA ratios

Anchovy larvae (Engraulis anchoita) were sampled from an area of upwelling in the subtropical waters over the Brazilian shelf and from an area over the Argentinian shelf characterized by a tidal mixing front. They were analysed for their nutritional condition by measuring RNA/DNA ratios. The degree of starvation occurring in the two geographic areas was correlated to length distribution, developmental stage and position in the water column. It was shown that starving larvae (5 to 80 %) were mainly found in the smaller length classes (4 to 10 mm SL), but some larvae between 16 to 20 mm SL were also determined as starving (4 to 6 %). Larvae found in the stratified water column had higher RNA/DNA ratios reflecting a better nutritional condition than in the mixed water body. The degree of starvation at the same developmental stage was higher in Brazil than in the Argentinian area. RNA/DNA ratios of larvae from the Argentinian area showed a significant shift to higher values (indicating a better condition) than in Brazil. Results on the nutritional condition of the larvae based on RNA/DNA ratios were compared with zooplankton data and larval gut analyses determined on the same cruise. Speculations on the survival strategies of these two anchovy populations are give