Searsport students set up clam survival experiment at three sites

By Jordan Bailey | May 24, 2017
Photo by: Jordan Bailey Searsport District High School student Kaden Harriman, left, and marine biologist Dr. Brian Beal hammer stakes around screened recruitment boxes. Clams that settle into the boxes will be protected from predators.

Searsport — Searsport District High School students recently helped a marine biologist set up a long-term clam experiment that yielded remarkable results when conducted on other parts of the coast.

Dr. Brian Beal, a University of Maine at Machias professor, designed and coordinated the experiment to test how much of a role predators play in the survival rate and distribution pattern of clams in the intertidal zone, the area of shore between the high and low tide lines that is exposed as the tide goes out.

On May 19, students placed several empty 1- by 2-foot, 3-inch deep wooden frames, covered in heavy duty screening, in the mud, and will open them up in the fall to count how many clams and other organisms are inside.

Clams have many predators: invasive green crabs, moon snails, ribbon worms, seals and gulls, to name a few, and the screens would protect clams that settle out of the water into the boxes during the microscopic phase of their life cycle.

“When we did this experiment in Freeport, you won’t believe what happened,” Beal told the students during a presentation at the school May 11.

He said Freeport students were surprised that boxes placed in the mud empty in April were full of clams when they opened them in November. One of the boxes had more than 6,000 clams inside, he said, while in the mud next to it there were just two.

Over his 30 years of researching, and when he was a clam digger as an undergrad at Maine Maritime Academy, Beal has observed that clams are more densely settled closer to the high tide line than in lower areas, and he wanted to find out why.

He said there are several factors that could contribute to this distribution pattern. It could be related to how microscopic clams settle out of the water (once they settle they don’t move much), or to ocean acidification, or to greater exposure to predators or a disease present at lower tidal heights. The experiment Searsport students set up focuses on exposure to predators.

In addition to the screened "Beal boxes," students placed protected and unprotected plastic flower pots into the mud at different positions within the intertidal zone. Each pot contains 12 juvenile clams supplied by the hatchery at Downeast Institute on Beals Island, where Beal is director of research. Half of the pots are covered in screen material and half are open at the top, with just a lip of screening around the edges to prevent the clams from digging their way out.

In the fall, the students will return to measure and count the clams in each pot. Fewer than 12 would mean some didn’t survive; more than 12 would mean that wild clams settled in the pots. The students will compare the survival rates between the protected and unprotected pots, and between those in the upper and lower areas of the intertidal zone.

Students spent the morning May 19 setting up the pots and boxes at three sites: either side of the causeway at Sears Island and Grants Cove in Stockton Springs. The sites are marked with orange wooden stakes.

Bob Ramsdell, chairman of Searsport's Shellfish Management Committee, said he is interested to see the results in the fall and will compare them to a similar study he worked on with Beal about 15 years ago in Stockton Springs.

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Jordan M Bailey
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Jordan Bailey has been working for The Republican Journal since 2013. She studied philosophy at Boston College and has experience in marine science education and journalism. She lives in Belfast.

 

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