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.