STANDISH (AP) – A researcher at St. Joseph’s College has discovered that many of the soft-shell clams that die in Casco Bay are not victims of predators after all.

For more than 40 years, researchers have believed that juvenile soft-shell clams were being eaten.

But Mark Green’s research shows that a large percentage of the tiny clams die because their shells were dissolved by acids created by natural reactions in the surrounding sediment.

Green said he hopes his research will lead to ways to give a boost to the $12 million industry in Maine.

“If we know what kills the juvenile clams, we may be able to substantially increase the yield of the commercial harvest by modifying sediments so that juveniles are no longer exposed to these natural acids,” he said.

Green said buffering sediments with calcium carbonate when clams are seeded may help protect the clams’ fragile shells.

Decreasing the mortality rate by several percentage points would translate to a potentially huge increase in yield, he said.

Scientists first noticed the loss of clams in the 1960s but no one knew for certain how they died. Finding an answer wasn’t easy because juvenile clams can’t be seen without a microscope, he said.

His research focused on hauling up sediment from five stations in Casco Bay and examining them in his lab.

His research showed that juvenile clams settle in Casco Bay during early summer when the pH balance of the top layer of sediment is relatively low, “making the very small clams susceptible to dissolving,” he said.

His research, which was produced with the help of graduate students, is published in the current issue of Limnology & Oceanography.

AP-ES-05-11-04 1713EDT