Nutritional condition and otolith growth of Engraulis anchoita larvae: The comparison of two life traits indexes

Abstract

Engraulis anchoita larvae were captured in 16 surveys carried out at a fixed sampling station (EPEA) in the Argentinean Sea between 2008 and 2017. Nutritional condition and growth of 214 anchovy larvae were estimated through RNA/DNA index and analysis of otolith microstructure. Standard length, developmental stage, age, weight, otolith radius, recent otolith growth rate (RGR), daily otolith growth rate (DGR), RNA/DNA index (sRD) and a derived index of growth performance were determined for each larva. Significant differences in nutritional condition and otolith growth rates were found among seasons and developmental stages, with slower RGR and lower sRD in larvae captured during winter and in the preflexion stage. On a long time scale, a similar seasonal pattern was observed with DGR. However, the amount of variability explained by ontogeny and seasonality was not equal in both RGR and sRD indexes. RGR was better explained with the analyzed variables, while future studies are required to improve the understanding of the nature of sRD. We observed signs that spring and autumn would be the most propitious season for larval survival in a short time scale, while winter would be the worst one, both in short and in long term scale.