About the project
We propose to study the physical and biological mechanisms that generate and maintain a highly genetically structured population of cod in the Skagerrak water system. We hypothesize that a combination of oceanographic features (i.e., within fjords water circulation), spawning behavior (i.e. strong phylopatry), and ecological traits (i.e. lower mortality of locally retained early-life stages) contribute to maintain the observed genetic differentiation of the returning adults. It is thus proposed to (1) study the inflow of North-Sea larvae to Norwegian Skagerrak fjords with focus on linking physics with population structure and dynamics, and (2) to study the maintenance of costal cod populations within fjords focusing on linking physics, behavior and biology. Issue (1) involves improving models of the linkages between North Sea spawning cod and local fjord populations of cod in the Skagerrak, explicitly considering the sub-structuring of the North Sea cod population and the variability of the oceanic dynamics. Issue (2) involves a detailed field study of spawning site selection, egg retention, larval drift, and current patterns in two representative fjords, to understand the mechanisms for maintaining local populations. Furthermore issue (2) requires developing and analyzing evolutionary and physical models to assess the degree to which mature coastal cod spawn at optimal sites so as to maximize the probability of the spawning products staying within the fjord given the dynamics of the local water masses. Our proposed work, besides being highly relevant to manage an economically important Norwegian resource, also has broader ecological relevance, in that it addresses an issue at the core of evolutionary biology: the generation and maintenance of genetic structure in marine fish populations.
This project funded by the Research Council of Norway
Start: 1.1.2007. End: 15.09.2011.