Atlantic Cod (Gadus Morhua) Distribution and Abundance in Relation to Climate Change

Distribution of cod during springtime NMFS  trawl surveys, 1979-1981.  Note presence south of Hudson Canyon.
Distribution of cod during springtime NMFS trawl surveys, 1979-1981. Note presence south of Hudson Canyon.
Project Summary:

This study examined water temperature changes on the northeastern US continental shelf (as far back as 1905) as well as bottom temperatures and cod distribution patterns from 40 years of resource survey trawls. We used climate model predictions of sea surface temperature change, relationships between surface and bottom temperatures in different parts of the northeast shelf, and equations relating temperature and cod production, to forecast potential responses of Atlantic cod (Gadus morhua) to a warming ocean.

Significance

How have species populations changed through time? Are there any patterns in species populations that may be correlated with temperature? Can science predict what might happen to a species if ocean temperatures warm in the Gulf of Maine?

Climate change is one of the largest threats to global biodiversity. This project begins to answer the question of how Atlantic cod might respond to warming temperatures, providing an important model that may be used for other species.

  • Michael Fogarty, National Oceanic and Atmospheric Administration,
  • Lewis Incze, University of Southern Maine,
  • Katherine Hayhoe, Texas Tech University,
  • David Mountain, National Oceanic and Atmospheric Administration,
  • James Manning, National Oceanic and Atmospheric Administration,
Location:

Gulf of Maine and Mid-Atlantic Bight, Spring and Fall Surveys, 1963-2004

Project Detail:

Atlantic cod (Gadus morhua) have been a mainstay of New England fisheries since well before European settlement in the region. Their historical abundance and importance are evident in the patterns of trade of salt cod in colonial records and the “Sacred Cod” that has hung since 1784 in the rotunda of the State House of Massachusetts. Despite their central role in New England history and culture, cod in the Gulf of Maine are in fact at the southern end of their range (annual mean temperature of 12 °C has been determined to be the threshold for cod –Drinkwater 2005). Because temperature affects virtually all aspects of the biology and ecology of cod, from recruitment to growth and distribution, G. morhua is likely to be a sensitive indicator of the effects of climate change on marine systems.

In this study we examined the last forty years of National Marine Fisheries Service, Northeast Fisheries Science Center (NEFSC) data in order to establish baselines against which to assess potential effects of climate change on population and recruitment. The NEFSC data set includes the following data for each of the approximately 350 tows completed during each seasonal survey: catch enumeration by species, weight by species, size and age comparisons, incidence of disease, diet composition, as well as surface and bottom water temperatures. From this dataset, we found three factors that correlated with the decreased likelihood of cod occurring in a given trawl: depth, temperature, and year. Cod were less likely to be caught by individual trawls in deep water, in warmer water, and with the passing of years (there has been an overall decline in cod numbers through the forty years of data we examined).

Under various emission scenarios and atmosphere-ocean general circulation models, bottom temperatures in the Gulf of Maine are predicted to rise between 1 °C and 2 °C. We conclude that under the 1°C temperature rise scenario, the maximum yield for cod will decline by approximately 21%. Under a 2°C temperature increase we predict a 43% decline in maximum yield. At this higher temperature level, we predict that the stock would go extinct at fishing mortality rates which are marginally sustainable under a 1°C increase in temperature. These results qualitatively point to a decrease in yield and a decrease in resilience to fishing pressure under increasing temperature regimes.

References:
  • Drinkwater, KF (2005). The response of Atlantic cod (Gadus morhua) to future climate change. ICES J Mar Sci 62:1327-1337

The following paper resulted from this work:

Also see:

  • Confronting Climate Change in the U.S. Northeast Report
    Frumhoff, P.C., J.J. McCarthy, J.M. Melillo, S.C. Moser, and D.J. Wuebbles. 2007. Confronting Climate Change in the U.S. Northeast: Science, Impacts, and Solutions. Synthesis report of the Northeast Climate Impacts Assessment (NECIA). Cambridge, MA: Union of Concerned Scientists (UCS).