A report published in the American journal Science ‘Cascading Effects of the Loss of Apex Predatory Sharks from a Coastal Ocean’ suggests that the overfishing large sharks has allowed smaller sharks to eliminate bay scallops on America’s Atlantic seaboard.
The report is the work of the Canadian and American researchers Ransom A. Myers, Julia K. Baum, Travis D. Shepherd, Sean P. Powers and Charles H. Peterson, and develops a 2003 study that revealed rapid declines in great shark populations in the northwest Atlantic since the mid-1980s.
Apparently the disappearance of predatory species such as the bull, the great white, the dusky and the hammerhead has triggered an explosion of ray, skate and smaller sharks that feed on shellfish.
Sharks are targeted in numerous fisheries and are often snagged as by-catch by tuna and swordfish fishermen.
The new report claims that cownose rays have annihilated the scallop population off North Carolina, and that this has been ‘sufficient to terminate a century-long scallop fishery’.
The report concludes that, ‘Analogous top-down effects may be a predictable consequence of eliminating entire functional groups of predators’.