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

摘要

For fish populations occurring in coastal upwelling areas, the timing of spawning 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, however might represent a period of increased risk to eggs and larvae due to the harsh and variable oceanographic conditions. This study determined the mortality rates of egg and larval anchoveta in an area located close to the species' southern limit of distribution during its winter spawning season. Two temporal scales of variability, interseasonal (between years), and intraseasonal (individual daily cohort mortality rates) show that (1) mean seasonal mortality rates were not different between years and (2) mortality rates 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 individual cohort mortality rates, especially in 19