Atlantic Cod (Gadus morhua) –
Distribution and Abundance in Relation to Bottom Temperature

Fall Surveys, 1963-2004

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

Significance

Incorporating data from multiple data sets, this project looks more closely at the distribution of cod in the fall months and in relation to bottom type and temperature. This work shows that the shallower surface water has warmed, but that this is insufficient to explain the decrease in cod catches.

Cod Quartiles

Atlantic Cod Study

Cod abundance data in each figure are grouped by quartiles of the log10 transformed data for each period. Quartiles are color-coded, and the catch weights for each period are listed alongside. The first slide, shown at left, is a composite of all years, followed by 5-year composites. Quartiles emphasize the distribution patterns of cod.

1965-1969
1970-1974
1975-1979
1980-1984

1985-1989
1990-1994
1995-1999
2000-2004

Bottom Temperatures, NMFS Fall Bottom Trawl Survey, 1963 – 2005

The areas shown above were selected for cod-temperature comparisons.

Abundance and Temperature

The Southern Coastal Shelf and the Great South Channel were selected because they are the warmest and they had a reasonable number of positive tows throughout the time series.

Temperature and Depth

The above figures show temperature verses depth in the southern areas to see if shallower regions and deeper regions reveal different temperature histories. Data are directly from the fall surveys; any variations in the timing of the surveys were not included in this analysis.

Substrate

The coarse resolution of the World Wildlife Fund substrate layer, shown above, illustrates the basic substrate types in the Gulf of Maine.

Data Sources

Data

NMFS (National Marine Fisheries Service) Fall Bottom Trawl Survey 1963-2005:
Data are from NOAA’s Northeast Fisheries Science Center (NEFSC), Woods Hole, MA. Only tows meeting NEFSC criteria for standard tows were included. We gratefully acknowledge data and discussions with Michael Fogarty and David Mountain of the NEFSC.

Base maps

Canada:
Paskevich, Valerie, 20020401, CANADA: Eastern Canadian Provinces:, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Field Center, Woods Hole, MA. http://pubs.usgs.gov/of/2003/of03-001/data/basemaps/canada/canada.htm.

USA:
Paskevich, Valerie, and Environmental Research Institute, Inc. (ESRI), 20010331, USA: United States basemap data layer for the Gulf of Maine surficial sediment GIS project.: U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Field Center, Woods Hole, MA. http://pubs.usgs.gov/of/2003/of03-001/data/basemaps/usa/usa.htm.

Bathymetry:
USGS Digital bathymetry of the Gulf of Maine, constructed by Ed Roworth and Rich Signell. http://pubs.usgs.gov/of/1998/of98-801/bathy/index.htm.

U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Geophysical Data Center, 2001. 2-minute Gridded Global Relief Data (ETOPO2) http://www.ngdc.noaa.gov/mgg/fliers/01mgg04.html

Contours:
U.S. Geological Survey, and Paskevich, Valerie, 2003, NY_GOME_CONTOURS: New York Bight and Gulf of Maine bathymetric contours: U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Field Center, Woods Hole, MA. http://pubs.usgs.gov/of/2003/of03-001

WWF Benthic Substrate:
The substrate layer is a product of a WWF-Canada and CLF project Classifying and Mapping Physical Habitat Types (Seascapes) in The Gulf Of Maine and The Scotian Shelf: Seascapes Version to May 2003 by Hussein Alidina and John Roff. The data were displayed by the substrate field and the colors reflect the substrate as illustrated in Figure 5.12 of the report:
Classifying And Mapping Physical Habitat Types (Seascapes) in The Gulf Of Maine and The Scotian Shelf: Seascapes Version to May 2003
Metadata »

The Gulf of Maine Area Program does not guarantee the accuracy of the data products provided and is not responsible for the misuse or misinterpretation of those products.

NMFS NEFSC Bottom Trawl Survey 1963-2003
This bottom trawl survey data are provided by the Northeast Fisheries Science Center of the U.S. National Marine Fisheries Service in Woods Hole, MA, USA. This is the U.S. analog to the DFO Bottom Trawl Survey. Data is provided for 1963 through 2003.