U.S. GLOBEC: NWA Georges Bank.
Factors determining early-life-stage survival and recruitment variability in N. Atlantic cod:
a comparison between NW Atlantic and Norwegian Sea Systems

Lough, Gregory

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Project Summary

Basin-scale changes in North Atlantic ecosystems have been observed but the mechanisms and pathways between physical forcing and specific ecosystem responses have not been elucidated. Ecosystem shifts have been identified by proxies such as temperature, which can have direct and indirect effects on various trophic levels. For Arcto-Norwegian cod, there is a strong relationship between early larval survival to recruitment and temperature through effects on feeding, metabolism, and growth, or as a proxy for other climate parameters, such as the advection of zooplankton-rich Atlantic waters from the Norwegian Sea onto the adjacent shelves. For Georges Bank cod and haddock, recruitment can be more complex, but recent studies have indicated that growth and survival of larvae was related to low surface salinity, a proxy for the influx of fresh Scotian Shelf water, ultimately leading to an increase in copepod populations as prey for larvae.

The objective of the proposed study is to develop an understanding of the processes controlling recruitment of cod and haddock on Georges Bank and cod in the Norwegian Sea sufficient to parameterize useful recruitment models and to forecast likely changes in abundance under a range of climate change scenarios. We will use the detailed information and understanding gained from modeling, broad-scale and process studies completed for a limited number of years in both systems to develop recruitment models and a suite of proxies that can be used to recreate the patterns and trends of longer recruitment time series for cod and haddock.

As part of the synthesis phase of GLOBEC we propose to establish comparative biophysical coupled model studies for transport and growth of larval and early juvenile fish in the two marine ecosystems Georges Bank and the Norwegian shelf/Barents Sea (the northern and southern extremes of the distribution of Atlantic cod). The study will be carried out in collaboration with colleagues at the Institute of Marine Research. These comparative studies will contribute to basic understanding of the interactions between fish populations and zooplankton and how these interactions are influenced by climate variability and change. The joint efforts will include:

  • Modeled basin-scale circulation fields with increased resolution within the regional domains of the two ecosystems
  • Lagrangian (particle tracking) models for application within the regional domains
  • Individual-based trophodynamic models for larval and early juvenile fish growth to be embedded in the regional circulation models
  • Hybrid (full life-cycle) recruitment models that build on results and understanding gained from the detailed process studies and biophysical models.