Offshelf Ekman Transport and Larval Fish Survival in the Northwest Atlantic

Abstract

We test the hypothesis that the survival of fish eggs and larvae is reduced by wind-driven transport off the continental shelf. A simple Lagrangian model including Ekman dynamics and vertically migrating larvae is developed to determine the cross-shelf movement of eggs and larvae in a two-layer stratified ocean; long-shelf movements are neglected. Wind stress calculated from 6-hr geostrophic winds for 1946 to 1986 is used in the study. Much of the variability in Ekman transport occurred on decadal time scales. Vertical migration, simulated by moving larvae into and out of the mixed layer diurnally, is found to significantly reduce horizontal advection by Ekman transport. No relationships are found between simulated Ekman transport of eggs and larvae and subsequent recruitment in the 8 Northwest Atlantic stocks investigated.