Modelling the timing of plankton production and its effect on recruitment of cod (Gadus morhua)

The match-mismatch hypothesis. which relates timing of plankton production to recruitment of fish, is difficult to test for a number of reasons. not least of which is lack of adequately resolved spatial and seasonal data for matching information on fish larvae and their food. Spatial, seasonal, and interannual variability of water-column stratification. primary production. and copepod egg production can be modelled. but do such models adequately represent features of interannual variability that affect survival of fish larvae? Information on the timing and location of cod larvae in the Irish Sea and at Iceland is used to identify target areas for which long-term hindcasts of plankton production are made using a one-dimensional model of water-column stratification and production of chlorophyll and copepod eggs, driven by hourly meteorological data. Hindcast spring chlorophyll and nitrate values for Faxa Bay (Iceland) in 1966 correspond well with observations. Hindcast interannual variability in Calanus egg production appears to have a significant effect on cod recruitment in the Irish Sea and at Iceland. While the conclusions from such a limited study must be tentative, they suggest that local meteorological forcing, in areas where cod larvae occur, exerts an effect on their survival, owing to the match between plankton production and larval feeding.