Climate Variability & Marine Fisheries

Species found in bottom trawl surveys on the continental shelf of the U.S. Atlantic coast north of Cape Hatteras were analyzed for their sensitivity to changes in ocean temperature seasonally and from year to year. Some shallow water fish (winter flounder, windowpane, and yellow flounder) stayed in their same general locations and depths despite seasonal changes in bottom temperature of 7° to 8° C. Some fish from the Gulf of Maine (witch flounder, American plaice, white hake and pollock) avoid temperature variations by staying year round in water more than 100 m deep where temperatures only vary by 1° to 2° C. Other types of fish, especially warm water migratory species (black sea bass, bluefish, scup, northern sea robin, summer flounder, and butterfish) were more likely to move to shallower warm areas in the summer as ocean temperatures increased. Some of these species like bluefish and black sea bass moved farther south in the winter, while others like butterfish moved offshore into deeper waters. Cool water migratory species (Atlantic herring, Atlantic mackerel and short-finned squid) moved north, staying in cool water, as temperatures increased in the summer.

Changes in Butterfish Distribution Click on image to enlarge

Hypothesized Fisheries Reponse To Climate Change Click on image to enlarge

If global warming leads to 1°C warmer waters in fall and winter on the continental shelf, these migratory species could occur as much as 25 to 50 nautical miles farther north and in shallower areas during the winter and early spring, and perhaps north during summer as well. This is likely to affect the fishing locations for these species. It may also affect the food chain by moving migratory forage fish into new areas where they may not be available to some of the sedentary predators currently feeding on them, but may be vulnerable to other predators in the new areas. This analysis gives us a first clue as to what might happen as ocean temperatures warm. There is still much to understand about the linkages within these systems and the different responses of individual species. Other parts of the life cycle such as reproduction will still need to be studied to estimate the possible impact of global warming on the life cycles of different species.

(For a related species response example, go to: Impacts of Warming On Estuary Dependent Marine Species on the Atlantic Coast)

TEXT REFERENCE:

1)	S. A. Murawski. 1993. Climate Change and Marine Fish Distributions: Forecasting From Historical Analogy. Transactions of the
	American Fish Society. 122 (5):647-658.
2)	Gomes, M.C., Haedrich, R.L., and Villagarcia, M.G. 1995. Spatial and Temporal Changes in the Groundfish Assemblages On
	the North-east Newfoundland Labrador Shelf, North West Atlantic, 1978-1991. Fisheries Oceanography. 4: 85-101.
3)	Montevecchi, W.A. and Myers, R.A. 1997. Centurial and Decadal Oceanographic Influences on Changes in Northern Gannet
	Populations and Diets in the North-west Atlantic: Implications for Climate Change. ICES Journal of Marine Science. 54: 608-614.