BAR HARBOR — Areas in Bar Harbor where clam production has decreased are undergoing testing to determine how and why that production has slowed.
Members of the Bar Harbor Marine Resources Committee, along with Heidi Leighton of the Maine Department of Marine Resources, reseeded two areas along the western shore and Hadley Point where clam production has generally been high.
“The purpose of the project is to test to see where clams are settling,” said Leighton, Eastern Maine area biologist under the DMR’s Shellfish Management Program. “There are some questions about it since clam production is not as high as it has been.
“Are clams naturally settling on those flats, and something is happening? Or are they not settling at all?”
Leighton, along with members of the Bar Harbor Marine Resources Committee, planted seed boxes last month. More reseeding locations are planned.
“The seed boxes are basically like a blueberry box that we buried halfway through mud in the flats with the top edge of the box sticking out of the mud,” Leighton said.
Some of the treatments were covered with protective netting; some have no netting. If the protected boxes produce juvenile clams, then researchers will know that the problem is predation. If the covered boxes do not produce clams, then the issue is reproductive.
“We will leave them out all summer and take a look in fall and see if we captured any of this year’s juvenile clams,” said Leighton.
The biologist said her hypothesis is that green crabs and ribbon worm are the likely predators.
“[Ribbon worm] is a native species, so those are something we’ve had for a long time, but they appear to be in higher numbers in Bar Harbor,” Leighton said. “Some [shellfish] harvesters are concerned pH is changing because of warming ocean temperatures.”
Another hypothesis is that the clams simply aren’t reproducing at all.
“We don’t know for sure, maybe the problem is in the reproductive end,” said Leighton. “This box is a way to see if and where clams are settling out of the water column.”
She said this kind of research isn’t as widely done as clam enhancement, where wild seed is planted in an area known for settlement.
Similar research has been successful in other states and has recently been implemented in Jonesboro, Gouldsboro, Steuben, Penobscot and George’s River in South Thomaston.
“We didn’t get any definitive answers, so [the goal] is to increase the size of projects and geographic area to see where they work, where they don’t work,” Leighton said. “Certain techniques work in some areas and not others. There are so many environmental variables.”