Factors determining early-life-stage survival and recruitment variability in N. Atlantic cod: a comparison bewteen NW Atlantic and Norwegian Sea Systems

F. Werner (UNC), R. G. Lough (NEFSC), T. Durbin (URI), D. Mountain (NEFSC), M. Fogarty (NEFSC), L. Buckley (NEFSC)

We propose a comparative study of the ecosystems on Georges Bank and the Norwegian shelf/Barents Sea. Collaboration with Norwegian colleagues at the Institute of Marine Research (Bergen) is a key component of our work. Focusing on specific years, our common 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. The understanding of these processes will be included in a model of cod recruitment through the adult stages. Our overarching hypothesis is that recruitment of cod and haddock is determined by variability in survival during the egg and larval stages that is constrained by density- and habitat-dependent factors operating during the early juvenile period. Two sub-hypotheses will guide our proposed work:

Our approach will include the implementation of:

  1. Physical and biological fields computed on a basin-scale that will allow for the evaluation of the relative importance of local vs. advective/upstream effects in the two systems.

  2. Lagrangian models within the regional domains which will enable us to quantify retention and transport and their variability in the two systems.

  3. 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. A suite of indices or proxies for factors and processes affecting early-life retention/transport, growth and survival.

  4. Models linking the dynamics of adult populations with physical and biotic factors affecting recruitment

Intellectual Merits:

The proposed model-based study will synthesize research findings of the Georges Bank program in the context of basin-scale phenomena in the North Atlantic. The approaches we will use are at the forefront of coupled physical/biological process and modeling studies, and the knowledge gained will be used to quantify the response of upper trophic components of the marine ecosystem to basin-scale and climate variability with particular reference to the target species cod and haddock. Broader Impacts: The inter-comparison of the NW Atlantic/Georges Bank with the Norwegian Sea system, allows for a generalization of our approaches and their relevance to other locations. As such, the results of our study are directly relevant to the ongoing Synthesis and Integration activities of GLOBEC programs in the US and internationally. 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. The models so formulated will be relevant tools to resource managers, thus linking studies of basic processes with applied practice. All our results will be made publicly available on the web so that interested students, teachers, scientists or resource managers can make use of them.