Mesoscale physical processes and the distribution and composition of ichthyoplankton on the southern Brazilian shelf break

Abstract

The southern Brazilian shelf supports the largest fish stocks in the country, and studies on physical–biological processes in the ecology of ichthyoplankton have been recommended to provide a better understanding of the variability of the recruitment of fishing resources. This study is the first to examine the influence of mesoscale physical processes on the distribution of early life stages of fish in this shelf-break region. Collections of fish eggs and larvae and measurements of temperature and salinity were made at 13 stations along cross-shelf transects in December 1997. Myctophidae, Bregmacerotidae, Clupeidae, Synodontidae and Engraulidae were the most abundant larvae in the northern region, while Engraulidae and Bregmacerotidae prevailed further south. In situ hydrographic data NOAA/AVHRR images and merged TOPEX/POSEIDON + ERS-1/2 satellite altimetry taken during the cruise revealed an anticyclonic eddy dominating the shelf around 31S. Larval fish abundance was lower at the centre of this feature, suggesting that the eddy advected poorer offshore waters of tropical origin towards the inner shelf-concentrating the larvae around the eddy.