There is no silver bullet solution to managing the complicated Atlantic bluefin tuna fishery.

These slow-growing but lightning-fast fish are highly migratory, a fact that can skew regional stock assessments. Changing ocean water temperatures as a result of climate change mean that where these predators can find enough food to sustain their 500-pound bodies is also changing.

The age at which the fish reach sexual maturity can vary by as many as six years, making it difficult to gauge how stocks will rebound from overfishing. And the type of gear used to catch Atlantic bluefin ranges from single harpoons to multiple drifting longlines, a fact that divides the fishery into a dizzying array of sub-categories.

“The only predictable thing about Atlantic bluefin tuna management is that it is very unpredictable,” said Walt Golet, an assistant professor at the University of Maine School of Marine Sciences and a research scientist at the Gulf of Maine Research Institute, or GMRI.

Golet pointed, for example, to a report on the 2020 stock assessment released in March 2021 by the National Oceanic and Atmospheric Administration that indicated a quota cut could be warranted – meaning fishermen would be allowed to catch fewer bluefin tuna. But in just the four months since the report was released and after questions about its findings, the federal government has agreed to do another assessment. Separately, regulators and scientists are working on new assessment models that will allow them to target different stock recovery requirements, like managing for immediate maximum yield or managing for long-term harvesting, when drafting a fishery management plan.

Golet’s research centers on understanding where the bluefin tuna caught in the Gulf of Maine have been before they arrive here. Atlantic bluefin tuna typically arrive here in early June and stay through September, though a few hang around until early winter.

Golet works with a network of fishermen to understand how bluefin tuna tap into habitats across the North Atlantic to feed and grow. The fishermen provide data on the size of the fish, and when and where they were caught. Also, Golet and his students take tissue samples for DNA analysis from a smaller number of fish and extract their otoliths, small bonelike structures in the fish’s head. Much as growth rings record information about the life of a tree, the otoliths record information about the life of the fish. Combined, the DNA analysis and the fishermen’s data provide Golet’s team a complete picture of where the fish was born, its overall health and its eating habits.

This information is important to bluefin fishery management because Atlantic bluefin tuna stocks have historically been controlled based on the origin of the fish, and research has previously shown that bluefin tuna from the Eastern Atlantic and Mediterranean are in better shape than those from the Western Atlantic. But both the DNA and the otoliths that Golet studies indicate significant levels of mixing between Eastern and Western bluefin tuna, a finding that could further change how management parameters are set in the future.

Despite the challenges, regional, national and international regulatory bodies manage the bluefin fisheries, because eaters worldwide have a large appetite for bluefin tuna, which is a popular standby for sushi. Given the consumption pressure, sustainable seafood guides like Monterey Bay Aquarium’s Seafood Watch tell eaters to avoid bluefin altogether, no matter where it is caught, and instead opt for other types of tuna, like skipjack and yellowfin.

So what’s a sustainable seafood eater in Maine to do when presented with locally caught Atlantic bluefin tuna?

Raw yellowfin tuna, left, and bluefin tuna. The sustainability of the bluefin tuna fishery poses a complicated question. Ben McCanna/Staff Photographer

“When it’s caught by Maine fishermen, it’s a really special, seasonal seafood, and we’re lucky to have it,” says Kyle Foley, Sustainable Seafood Senior Program Manager at GMRI. Her sentiment is echoed by some Maine chefs.

“Atlantic bluefin tuna … has absolutely experienced a renaissance due to the strict regulation and monitoring of the harvest,” said Jesse Souza, executive chef at Front & Main in Waterville. “This regulation has brought our local bluefin back and established it as a sustainable product that we can feel good about having in our kitchens and on our plates.” Souza buys his bluefin from Harbor Fish in Portland and believes the fish should be treated simply in the kitchen to showcase its natural combination of fattiness, salinity and melt-in-your-mouth texture.

Kirby Sholl, chef de cuisine at Chaval in Portland, says he enjoys working with bluefin tuna because it can hold its own against big flavors like chilies, soy sauce and wasabi. He knows when he gets in an order from fishmonger Browne Trading and puts it on the menu, it will sell, a point no chef can take lightly as restaurants struggle to recover from pandemic losses. But he also serves it because he trusts Maine fishermen, who have in the past adhered to measures – some mandated, others voluntary – to protect future stocks of other popular seafoods like cod, halibut and lobster.

As the regulations stand today, permitted commercial vessels fishing in the Gulf of Maine can pull in three bluefin tuna per fishing trip until the national quota for them is reached annually. Despite the low cap, though, Maine fishermen are willing to fish for bluefin because a single fish can sell for as much as $15,000. The retail price for bluefin tuna in Portland is between $20 and $40 per pound.

Making sure that none of a big tuna gets wasted is one way consumers can ensure their choice is a sustainable act, said Jen Levin, president and CEO of Gulf of Maine Sashimi, a fish purveyor in Portland. At the height of the season, she expects to be processing about three bluefin tuna per week into loin, belly and fatty belly cuts, which she sells to restaurants and directly to customers via the company’s website. Chefs may special order cheeks and tails as well. So if you see Maine bluefin tuna on a restaurant menu, you can rest easy that it’s OK to eat it.

Christine Burns Rudalevige is a food writer, recipe developer, tester and cooking teacher in Brunswick, and the author of “Green Plate Special,” a cookbook from Islandport Press based on these columns. She can be contacted at: [email protected]

Baste the tuna kebabs on the grill with a spicy, Asian-inspired marinade. Ben McCanna/Staff Photographer

Hot and Sweet Tuna Kebabs and Melon Salad

This recipe will work with any meaty fish, including bluefin and yellowfin tuna, shark, swordfish and dogfish. 

Serves 4

FOR THE KEBABS:
2 (3/4-pound) pieces raw tuna loin
3 tablespoons olive oil
2 tablespoons honey
2 tablespoons soy sauce
1 tablespoon grated ginger
1 tablespoon Asian garlic and chili sauce
1 teaspoon ground allspice
4 wooden skewers, soaked in water for an hour
1 tablespoon sesame seeds, for garnish

FOR THE SALAD:
Zest and juice from 1 lime
1 tablespoon soy sauce
1 tablespoon fish sauce
1 teaspoon honey
1 teaspoon sesame oil
1 teaspoon minced fresh Fresno chili pepper
4 cups mixed watermelon, honey dew and cantaloupe balls, in 1-inch chunks
1/4 cup cilantro leaves
1/4 cup thinly sliced scallions
3 tablespoons pickled ginger, roughly chopped

Cut each of the tuna loins into 8 similarly sized chunks.

In a medium-sized bowl, combine the olive oil, honey, soy sauce, ginger, garlic and chili sauce, and allspice. Transfer half of the marinade to a small bowl and set aside. Toss the tuna chunks with the marinade remaining in the medium bowl. Set in the refrigerator to marinate for 30 minutes.

To cook the tuna, thread 4 pieces of the marinated fish onto each skewer. Preheat a grill to medium high heat. Place skewers on the grill. Cook on the first side for 2 minutes. Rotate the skewers to cook on each subsequent side for 1 minute.  A total cooking time of 5 minutes will render the tuna pieces medium rare. Remove from the grill and brush with the reserved marinade and sprinkle with sesame seeds.

To make the salad, combine lime zest and juice, soy sauce, fish sauce, honey, sesame oil and chili. Add the melon, cilantro, scallions and pickled ginger. Toss to coat the melon with the dressing and serve with the tuna kebabs.


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