Early life survival of the anchoveta Engraulis ringens off central Chile during the 1995 and 1996 winter spawning seasons

For fish populations occurring in coastal upwelling areas, the timing of sp awning has been proposed to occur during seasons when transport offshore is reduced. Along the coastal zone off central Chile, the anchoveta Engraulis ringens spawns preferentially during winter. Spawning in this season, howe ver might represent a period of increased risk to eggs and larvae due to th e harsh and variable oceanographic conditions. This study determined the mo rtality rates of egg and larval anchoveta in an area located close to the s pecies' southern limit of distribution during its winter spawning season. T wo temporal scales of variability, interseasonal (between years), and intra seasonal (individual daily cohort mortality rates) show that (1) mean seaso nal mortality rates were not different between years and (2) mortality rate s considering the egg and larval stages together (96% daily in 1995 and 98% daily in 1996) were much higher than those estimated using only the larval stage (4.4% daily in 1995 and 6.8% daily in 1996). The results of the indi vidual cohort mortality rates, especially in 19$5, revealed a tendency towa rd a decrease in mortality rates as the winter season progressed (from 52 t o 9% daily). Because the maximum egg abundance in the water column occurred early in the season in 1995, we propose that the largest fraction of the m ean seasonal mortality was due to egg mortality occurring early in winter. The information on the environmental characteristics and the reported larva l growth rates in different periods during the winter spawning season do no t support the hypothesis of larval food limitation but, instead, suggest th at oceanographic factors (e.g., cross-shelf transport, low water temperatur e, presence of river plumes) play a major role in the development and succe ss of the early life stages in this southern spawning area.