Optimal environmental window and pelagic fish recruitment success in upwelling areas

Food availability and physical constraints such as turbulence are important factors affecting larval survival and pelagic fish recruitment. Food availability for larvae is related to primary production up to a point where the biological process are disturbed by physical processes (turbulence generated by wind mixing). This limitation does not exist for non Ekman-type upwelling where upwelling intensity is not correlated with wind speed. We hypothesize that relations between annual recruitments and upwelling intensity are dome shaped in Ekman-type upwellings and linear for non Ekman-type upwellings. Recruitment of Peruvian anchoveta Engraulis ringens, of Pacific sardine Sardinops sagax caerulea and of the West African sardines and sardinellas are thereby examined. For Ekman-type upwelling the annual recruitment increases with upwelling intensity until wind speed reaches a value of c5-6 m.s-1 and decreases for higher values. For a non Ekman-type upwelling the relationship between recruitment and upwelling intensity is linear. Results confirm the existence of an optimal environmental window for recruitment. -from Authors