Fishery biologist Sandy Sutherland looks through the lens of the microscope at tiny sections of fish earbones, known as otoliths, each showing annual bands of growth. She carefully counts the bands to determine the age of the fish, then moves on to the next sample.

A team of Canadian and American scientists says that the overfishing of large sharks has led to an explosion of small predators that are devastating populations of shellfish. Sharks usually do not evoke sympathy, but a new study could change that.

Fewer big sharks in the oceans mean that bay scallops and other shellfish may be harder to find at the market, according to an article in the March 30 issue of the journal Science, tying two unlikely links in the food web to the same fate.