This study compares the ecosystems on Georges Bank and the Norwegian shelf/Barents Sea via a collaboration with Norwegian colleagues at the Institute of Marine Research (Bergen). The objective is to develop a better understanding of the interactions between fish populations and zooplankton and how these interactions are influenced by climate variability and change. This understanding will be incorporated into a model of cod recruitment through the adult stages.
The overarching hypothesis is that recruitment of cod and haddock is determined by variability in survival during the egg and larval stages, which is constrained by density- and habitat-dependent factors. Two sub-hypotheses assert that (Ho1) advection of Scotian shelf water into the Gulf of Maine and (Ho2) advection of zooplankton-rich water from the Norwegian Sea into the Barents shelf increases larval cod/haddock growth and survival in each system. The approach includes: 1) Computation of physical and biological fields on a basin-scale to evaluate the relative importance of local vs. advective/upstream effects in the two systems. (2) Implementation of Lagrangian models within the regional domains to quantify retention and transport and their variability in the two systems; (3) Implementation of spatially-explicit individual-based models for larval and early juvenile fish growth which, when coupled with the observed prey data will provide growth rates in the two systems. (4) Development of asuite of indices or proxies for factors and processes affecting early-life retention/transport, growth and survival. (5) Development of models linking the dynamics of adult populations with physical and biotic factors affecting recruitment . The inter-comparison of the NW Atlantic/Georges Bank with the Norwegian Sea system, allows for a generalization of the approaches and their relevance to other locations. The development of indices based on the detailed process studies will be used to develop, parameterize and evaluate hybrid recruitment models linked to the dynamics of adult stocks of commercially important species. All results will be made publicly available on the web so that interested students, teachers, scientists or resource managers can make use of them.
