Researchers studying the sharp decline between 1980 and 2010 in documented landings of the four most commercially-important bivalve mollusks – eastern oysters, northern quahogs, softshell clams and northern bay scallops – have identified the causes.
Warming ocean temperatures associated with a positive shift in the North Atlantic Oscillation (NAO), which led to habitat degradation including increased predation, are the key reasons for the decline of these four species in estuaries and bays from Maine to North Carolina.
The NAO is an irregular fluctuation of atmospheric pressure over the North Atlantic Ocean that impacts both weather and climate, especially in the winter and early spring in eastern North America and Europe. Shifts in the NAO affect the timing of species’ reproduction, growth and availability of phytoplankton for food, and predator-prey relationships, all of which contribute to species abundance. The findings appear in Marine Fisheries Review.
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Image: Clyde Mackenzie with MV shellfish constables Warren Gaines and Jason Mallory. Photo CREDIT: Deborah M. Gaines