Midcoast shellfish harvesters have documented an abundance of wild oysters, once considered a rarity, in the Damariscotta and Medomak river estuaries.
University of Maine professor Heather Leslie said the growth in the midcoast oyster farming industry may have something to do with the increase in the wild population.
"As we've seen oyster farms increase, we've also seen an increase in wild American oyster populations," she said.
Harvesters have suggested that larvae raised on oyster aquaculture farms had reached the intertidal zone and recruited as wild oysters.
At the same time, the softshell clam population has declined significantly, as much as 90% in the upper Damariscotta River estuary, according to a recent study from the University of Maine in collaboration with local shellfish harvesters.
There's no single reason for the softshell clam population's decline, Leslie said.
"We know that the ocean environment is changing; the chemistry and the temperature of the water, of this estuary and other Maine estuaries, have changed through time," she said. "We know that the green crabs have taken advantage of some of those changes in ocean conditions, and they're really voracious predators. And we know that many Maine mudflats are heavily harvested by people as well."
Researchers and shellfish harvesters are studying why and whether the population can be restored, Leslie said. The research is being shared with municipal shellfish committees.
