Ecology of Planktonic Atlantic Cod (Gadus morhua)

Abstract

Atlantic cod larvae surviving the irst weeks after hatching setle next years juvenile recruitment on Georges Bank (USA). It probably supports Hjort’s critical period hypoth-esis that efects of climate on marine biological productivity control early-life history processes and recruitment in ish populations. Climate also regulates local ultraviolet sea surface radiation, which may potentially killmicrobes pathogenic to planktonic cod eggs. Survival capacities of cod larvae depend on maternal efects on egg qualities atained during oogenesis, inluenced by variable food sources for female cod. Actual survival of irst-feeding cod larvae requires proper abundance of preferred prey, cope-pod nauplii, produced by fertile females. Temporal and spatial mismatch between cod larvae and prey is normal, extensive and lethal, counteracted by opportunistic behavior that optimizes encounters. In spawning habitats of Northeast Arctic cod, the abundance of Calanus inmarchicus nauplii possibly results from coastal biological productivity in the previous year, which may explain time lags in positive correlations between vernal river discharge and NEA cod recruitment. Extensive meltwater storage for year-round hydroelectric production probably limits food web productivity, survival of NEA cod larvae and stock recruitment. Global climate change and stock management interact eco-logically with other anthropogenic inluences concerning sustainability of Atlantic cod population systems.