Population dynamics of cod Gadus morhua in the North Sea region: biological density-dependent and climatic density-independent effects

Abstract

Through the statistical modeling of monitoring data, we assess the ecological interlinkages between cod Gadus morhua L. in the North Sea, Skagerrak and Kattegat—regions which typically have been considered separate management units. The model includes both within-population density dependence (within and between age classes), as well as density-dependent effects of migration between the North Sea, Skagerrak and Kattegat. Further, the model incorporates the effects of environmental features (such as temperature and the North Atlantic Oscillation). The obtained results are discussed, both with reference to general ecological principles as well as with respect to management implication. Altogether our analysis suggests a unified management regime for the entire region including the North Sea, the open Skagerrak and Kattegat.