Hard-Shell Clam Culture Could Offer New Opportunities

by Laurie Schreiber

Wearing hip waders and dragging a child’s plastic sled loaded with baskets, tools, bug dope and a camera in a Ziploc bag, clam harvester Joe Porada headed out across the mud flats at Goose Cove in Trenton just after 4 a.m. on a recent morning.

A full moon was descending into the distant treeline that surrounded the cove, and seagulls were beginning to awaken with many a squawk.

“The midges were extreme yesterday,” Porada said with his typically cheerful smile. “I was running to get back to my truck.”

Midges notwithstanding, mid-June at low tide before dawn is a quiet time of day in a beautiful kind of place. The sea grasses around the cove were an emerald green and the sky a hint of turquoise that deepened with the light. Porada walked easily across the grass and slippery rocks, and then into the sucking mud. He had to traipse to the mouth of the cove to harvest the wild soft-shell clams; the inner cove was closed to harvesting because of the presence of harmful bacteria in the water.

“It’s almost like cross-country skiing; toe first, then your heel,” he said of the strategy necessary to maneuver through the muck. “If you start off with your heel, you’ll form a vacuum and you’ll get stuck.” Porada lives in Hancock but has been spending lot of time in Goose Cove in recent years to tend the three contiguous two-acre experimental lease sites he has there to cultivate hard-shell clams, also known as quahogs. He also expects to begin cultivating oysters at one of the sites in the coming weeks.

Typically, he said, he tends the sites by boat, which he keeps at a friend’s property across the bay in Salisbury Cove. But today he was heading out to harvest soft-shell clams, also known as steamers, to sell to one of his customers. He would just be doing a routine check on the sites, and would fix one of the protective nets that had been shifted by the tide.

Originally from upstate New York, Porada said he landed in Maine in 1983 with $600 and a tent, after hitchhiking around following college. He stayed at Blackwood’s Campground in Acadia National Park, bartended awhile, then moved on to the food service industry in general. “Then I met some clammers, they took a liking to me, so I started clamming,” he said. He harvested soft-shell clams for a long time, then started digging quahogs.

“It seemed like a good chance to expand,” he said. “I realized there weren’t enough wild quahogs to make a continual living for the rest of my life, so I started looking into aquaculture.” He contacted Dr. Brian Beal, director of research at the Downeast Institute for Applied Marine Research and Education in Beals.

According to the institute’s website, the facility started Maine’s first shellfish hatchery in 1987 that spawned wild clams and raised them on a diet of cultured algae to produce seed clams for depleted municipal flats.

Over the next 16 years, the facility produced hundreds of millions of seed clams for more than 40 Maine coastal towns and a handful of communities in New Hampshire and Massachusetts. The hatchery has expanded its work to include other shellfish, including scallops and sea urchins. The program also conducts research on soft-shell clams, hard clams, lobsters and scallops. All of the institute’s field investigations involve Down East fishermen, the website says.

Porada is one of those fishermen, conducting what the institute said is a “business incubator project.” In 2005, Porada said he obtained some adult hard clams from Goose Cove and took them back to the institute. With funding from The Maine Technology Institute, institute staffers successfully spawned them, then reared the larvae and juveniles using techniques similar to those used to produce larval and juvenile soft-shell clams.

The hard clam seed grew to an average size of 8 millimeters in length in ocean-based nursery trays and was successfully overwintered at the institute’s Black Duck Cove facility. In May 2007, the hard clam seed was planted at Goose Cove in one of three experimental lease sites that Porada obtained through the Department of Marine Resources (DMR).

Porada said he and his partners at the institute won a U.S. Department of Agriculture grant to do the initial trials in 2008. In 2010, he said, they won a Phase Two grant of $400,000 to conduct several types of experiments to determine the optimal way to grow the animal. Porada said he plans in coming weeks to expand his experiments to include oyster cultivation on one of the lease plots.

Kyle Pepperman, a marine biologist at the institute, is assisting Porada with his work. Pepperman and Porada said the project has potential to grow millions of seed clams to marketable adults. And that will mean more opportunities for current and new fishermen, they said.

Pepperman said he assists Porada both in the field and the lab.

“I raise his seed and help him with research and seeding efforts,” he said.

The rearing process starts in January, Pepperman said. That’s when they bring in mature clams age 3 to 4. The clams are put through a process called thermal conditioning, which means gradually raising the water temperature in order to trick them into thinking it’s springtime. Pepperman also cultures the algae that goes into the animals’ rich diet.

After a month of thermal conditioning, the water temperature is raised a little bit more, which causes the hard clams to release sperm and gametes into the water, thus forming zygotes.

The water is then strained down on a fine-mesh sieve, which captures the tiny larvae, Pepperman said. After swimming around for the first two weeks of their lives, the clams settle onto big, mesh floating trays. The animals are raised to about 2 millimeters in diameter, a size that allows them to sit on window screen material, Pepperman said.

At that point, at the beginning of June, they can be transferred out to Porada’s lease sites.
The clams are brought back to the institute in November, when they’re about a quarter of an inch in diameter, and overwintered until the following summer.

“They’re very low maintenance,” Pepperman said. “At lower water temperatures, they go into stasis and don’t feed. We can keep millions and millions of them in a very small area and have great survival.” The following summer, the clams are returned to the ocean.

Pepperman said he’s been working with Porada on the project since 2006.

“It’s a great resource,” he said. “Joe is doing a lot of the legwork, and I think other people will see it and say, ‘I can do this as well.’” Goose Cove is the northernmost point in Maine where hard-shell clams are found, Pepperman said. The oval-shaped, soft-shell clams prefer colder water, and so they do fine anywhere off the Maine coast, he said.

The rounder, thicker-shelled hard clam prefers warmer water and can be found as far south as Florida, he said. Because the cove is broad and shallow, the water in Goose Cove is just warm enough for hard clams, he said.

“There are places along Maine coast where hard clams don’t grow,” he said. “But here we get quite a bit of warm water, and it’s enough to sustain a population. You can find hard-shell clams all along the coast of Maine, but they do really well in this cove.”

Porada said he’s been experimenting with different aspects of the cultivation process—putting nets over the lease sites, for example, results in a 90 percent survival rate because predatory green crabs are deterred from eating the young clams. Experiments without the nets results in a survival rate of less than 17 percent, he said.

Today, he had about 360,000 first-year hard clams at one site, and another 200,000 to 300,000 overwintered clams at another.

He said he also plans to set crab traps later this month, “to hopefully, at least, distract them,” he said. “They tell me not to expect to eliminate them.”

Because the sites are experimental, he is not yet selling the product. He said he plans to apply to the state at the end of the summer for a standard lease site to raise hard clams commercially. The plan is to use adults raised at the experimental site to stock the commercial site.

Porada’s is the only quahog aquaculture site in Maine. “I think it’s been thought of, but no one else has done it,” he said. “There’s not really good habitat in Maine for this, but in southern Maine they have plenty in the wild. I wanted to do it and it’s just something to keep me happy. It should work.”

Hard clams take only two or three years to grow to market size, about half the time it takes to cultivate soft-shell clams—making it a more cost-effective and faster turnaround on the initial investment, Pepperman said. Hard clams are also considered more of a delicacy than soft-shell clams and can earn harvesters a better price, he said.

“The smaller they are, the more they’re worth,” he said.

Pepperman said that Porada also plans to experiment with upweller designs to optimize growth. An upweller is a silo system which allows spat to sit on fine mesh at the bottom, and water to continually well up around the spat, so there is constant feeding. Upwellers are commonly used for oyster cultivation.

“They’re very inexpensive to manage and you can grow your seed large over the summer with the constant flow of nutrients,” Pepperman said.

A successful design for an upweller will help maximize opportunities for other fishermen wanting to grow hard clams, he said, by making it cheaper to buy the seed at a smaller and less expensive size and raise it themselves.

“We’re just trying to increase the infrastructure here by adding a new resource,” said Pepperman, “If millions of clams could be harvested here a year, instead of hundreds of thousands, that gives people jobs.”