I’ve written about sustainable seafood for about seven years now. But it wasn’t until last month that I boarded a boat in order to get a story. The small vessel was moored south of the Maine border on a pier at the University of New Hampshire’s Judd Gregg Marine Research Complex in New Castle. I weathered the choppy waters of the tidal Piscataqua River in spite of seasick tendencies because I wanted a closer look at the small-scale Integrated Multi-trophic Aquaculture (IMTA) system researchers are prototyping there in order to farm steelhead trout.

Steelhead trout are actually rainbow trout that start their lives in fresh water but mature in saltwater. They are typically found on the West Coast, where they are a highly protected species, but they are also farmed on a large scale in Chile. Since the 1940s, both state and private hatcheries in New Hampshire have released native East Coast rainbow trout into streams and lakes for recreational fishing. Should those fish make their way to the Atlantic, they too become steelhead trout.

The findings of the New Hampshire steelhead trout project, in place since 2014, show that fish hatched and raised to 10 inches in length in freshwater farms in Ossipee can then be transferred to the prototype net pens and grow to harvestable 5-pound steelheads in the warm coastal waters in about seven months. Which calendar months are best to grow out these trout in their saltwater habitat is still up for debate, the research finds, due to the rate at which the region’s seas are warming, says New Hampshire Sea Grant research scientist Michael Chambers. Fish have typically gone into the saltwater pens in May and been harvested in early November, but they are experimenting with transferring fish into the pens later in the year.

IMTA systems work like agricultural companion planting schemes. For example, Native American Three Sisters cluster plantings comprise maize (corn), climbing beans and winter squash because these species thrive together. The maize provides a structure for the beans to climb. The beans release nitrogen into the soil that the other plants use to grow. And the squash spreads along the ground, helping to keep the soil moist while blocking out the sunlight. Likewise, for IMTA aquaculture, different species of seafood share space and are mutually beneficial.

Chambers and his colleagues are developing rectangular net pen raft systems, two pens per unit, each holding about 2,000 female fish. The floating unit is anchored about a mile offshore and has 3-foot decks on all sides so researchers can feed and observe the fish. Dozens of ropes hang underneath the decks, upon which both blue mussels and sugar kelp grow. The mussels and kelp thrive on the nitrogen the fish excrete as waste, mitigating any negative environmental impact that nitrogen could have the local ecosystem, Chambers explains.

These low-tech systems are made from PVC pipes, pressure-treated wood and nylon netting. They are about 20-feet by 40-feet and are easily placed in the ocean, all factors that Chambers says make them affordable for local fishermen who are interested in steelhead trout farming as a way to diversify their income as fishing quotas and warming oceans take a bite out of their livelihood. He estimates that a system like this could yield 20,000 pounds of fish in a season with a market value of about $7 per pound.

Chambers says Maine’s long, protected coastline offers many feasible spots to set up steelhead trout farms. Additionally, Chamber’s team hopes to develop submergible systems that could be sited farther offshore and be pushed under the surface of the water in the face of bad storms that otherwise could toss the pens around, damage them and potentially allow the trout to escape into the sea. If do they get out, they could cross-breed with wild fish, but proponents point out these farmed fish are native to the East Coast. Another objection often heard to ocean-farmed fish is that they can pass diseases on to surrounding wild fish, but this IMTA approach helps keep diseases down, Chambers says. He also made it clear these pens are intended for small-scale farming, not for industrial fish production.

Christine Burns Rudalevige flakes Ducktrap smoked trout into a food processor.

While Maine has no steelhead trout farms, the University of Maine recently conducted a three-year study with Cooke Aquaculture to test whether mussels could grow alongside Atlantic salmon at Cooke’s sites in Machias Bay and Cobscook Bay, another example of IMTA aquaculture. The study demonstrated the two species could grow in conjunction and also that the mussels could ingest larval sea lice, an external parasite of the salmon that can be problematic for large fin fish farms, said Christopher Bartlett, a research scientist with the Maine Sea Grant program and the University of Maine Cooperative Extension. Cooke’s officials stopped mussel production after the research project concluded, Bartlett said.

The Steelhead trout being farmed in New Hampshire is an orange-fleshed fish that tastes a little like an earthier, sweeter version of farmed salmon, says award-winning chef Jeremy Sewall, who serves the fish in his restaurants whenever they are available. Sewall grew up in York, Maine, in a family of lobstermen. He is part-owner of Island Creek Oyster Bars in Boston and Burlington, Massachusetts, and Row 34 in Boston and Portsmouth.

Sewall first caught sight of the fish in his social media feed about three years ago and immediately called his fish buyer to ask for some. He became enamored with their flavor from his first taste. So enamored, in fact, he invested in the project to keep the farmed fish coming. He pays for the fish and the fish feed. But Sewall doesn’t keep the fish all to himself. He gets in line behind New Hampshire fishmongers like Sanders Fish Market in Portsmouth and Seaport Fish in Rye, New Hampshire, which, in turn, sell it to their retail and restaurant customers. “I like to get as much as possible, of course, because it’s fabulous fish, “Sewall said. “But it’s a local, sustainably produced fish first and foremost, so the majority of it should rightly be readily available to the community.”

ABOUT THE WRITER

CHRISTINE BURNS RUDALEVIGE is a food writer, recipe developer and tester and cooking teacher in Brunswick, and the author of “Green Plate Special,” a cookbook from Islandport based on these columns. She can be contacted at cburns1227@gmail.com