Copepod production drives recruitment in a marine fish

Abstract

Predicting fluctuations in recruitment of commercial marine fish remains the Holy Grail of fisheries science. In previous studies, we identified statistical relationships linking Atlantic mackerel ( Scomber scombrus ) recruitment to regional climate, zooplankton biomass, and the production of copepod nauplii over a decade (1982–1991) that included the exceptionally strong year class of 1982. Here we tested the validity of these relationships by adding a second decade (1992–2003) of observations that includes another exceptional year class in 1999. We provide the first field-based evidence linking availability of plankton prey in the sea to early growth of larval fish and to year-class strength in a commercially exploited marine fish. Recruitment is shown to strongly depend on production of the copepod nauplii species that contribute to the diet of mackerel larvae. Both strong year classes were characterized by exceptionally high availability of these specific prey. We suggest that mackerel recruitment can be anticipated 3 years in advance based on prey availability during the first weeks of planktonic life and predict a strong year class for fish hatched in 2006.