In 2012, local fishermen, tournament directors and scientists teamed up to pursue a common goal: data collection. Now, commercial tuna stocks, once depleted by overfishing, are on the rebound thanks to new management proposals informed by data from the University of Maine at Orono’s Pelagic Fisheries Lab. 

Walt Golet and Sammi Nadeau pose near a bluefin tuna caught at a local tournament. Sammi Nadeau photo

Walter Golet manages the lab, located at the Gulf of Maine Research Institute. His team analyzes tissue samples from bluefin tunas and other species caught at local contests to determine their age and migratory patterns.

“Often, fish are cleaned at sea,” Golet said. “Their internal organs — stomach, liver and gonads — are removed and thrown overboard. Our contacts at tournaments give us those samples after weigh-in, providing access to all sorts of information.” 

Over the years, the lab has worked with competitions, including the Bailey Island Fishing Tournament and the Bluefin Benefit Battle, as well as now-defunct events including the Sturdivant Island Tuna Tournament, now part of the Casco Bay Bluefin Bonanza. 

Golet’s team consists of graduate students exploring a range of projects, from movement and migration to foraging ecology. Bluefin tuna is one of the group’s focal points, given fishermen’s vested interest. 

Blaise Jenner, a team member and scientist at the Maine Department of Marine Resources, is studying bluefin foraging ecology. He said that stomach samples from local tournaments play a key role in identifying the species’ diet, informing a management framework to better protect predator and prey. 

The collaboration is not only beneficial for scientific research. 

“It’s great from an educational standpoint, too,” Golet said. “Often, we interact with the public when we show up for collection. This gives us a chance to fill them in on the work we’re doing to support the fishing industry.” 

Informing assessment models

Sammi Nadeau holds otoliths (ear stones) from a bluefin tuna to show the size and scale of the biological samples the Pelagic lab works with. Sammi Nadeau photo

One of the lab’s more extensive programs relates to estimating tuna population size.

“As a fishery scientist, you are constantly faced with the question of how many fish there are in the sea,” said Golet, laughing at the irony of the statement. “Boats want to catch as many fish as possible, and you want to make sure enough get left in the water to reproduce and complete the circle of life.” 

The team’s top priority is to improve the knowledge of bluefin biology to better inform stock assessments. To be clear, they do not evaluate the status of the stock — that is done in Madrid, Spain, by the International Commission for the Conservation of Atlantic Tunas. Instead, they provide biological data for scientists to inform assessment models and get a more accurate look at what’s happening in the Gulf of Maine. 

Based on field observations, Golet claims the tuna population is increasing. 

“Catch rates are higher,” he said. “Historically, the number and speed of fish brought over the docks is much greater than before. And that’s with regulations — commercial fisherman can only fish three days a week; the other four are prohibited because the National Marine Fisheries Service is trying to slow landings and extend the season.” 

Stock assessment is a complex mathematical model that relies on data from multiple nations, not just the United States. That said, Golet’s lab is the primary recipient of sample tissues throughout New England and farther down the mid-Atlantic to North Carolina — responsible for contributing much data to the global playing field. 

In 2017, Jenner worked as one of Golet’s summer technicians. His primary role was collecting otolith (ear stone) and muscle sampling from bluefin tuna in Massachusetts through Maine. Prior, he said he did not have much experience dealing with the commercial fishing business, let alone biological sampling.

Sammi Nadeau holds up an Atlantic bluefin tuna stomach — an example of the internal organs the lab analyzes to better understand species’ foraging habits. Sammi Nadeau photo

“One of the things that amazed me then, and still to this day, is how such a small part of the fish [otolith] tells so much about its life,” Jenner said. “I was fortunate to return to studying the bluefin tuna, picking up on the foraging ecology work Sammi Nadeau began in 2018.” 

The importance of long-term monitoring

In 2018, Nadeau, another student at the lab, saw a significant shift in the diet of bluefin tuna from herring to shortfin squid. In 2022, Jenner found yet another change — this time from shortfin squid to Atlantic menhaden. 

According to Jenner, long-term monitoring is crucial for fishery management; it’s important for the preservation of tuna and the species, such as Atlantic menhaden, on which it relies.

“Our work shifts the focus from the predator to the prey,” Jenner said. “So, when fishery managers set quotas, they consider the predator species’ food source and make sure to leave enough, in this case, menhaden, in the ocean for foraging.” 

Nadeau emphasized the importance of such research, pointing out that bluefin tuna swarm the Gulf of Maine from late spring through early fall. If their forage base is scarce of lipid-rich prey, they will migrate elsewhere, she said, impacting local fishermen’s success in harvesting the species they require. Moreover, if the condition of the species declines, leading to skipped spawning schedules, Mainers will feel it in their pockets.

“Bluefin tuna are prized for their melt-in-your-mouth texture as sushi and sashimi,” Nadeau said. “Foraging is a major contributing factor to tuna’s overall condition; if the forage is poor, we might see this reflected on a larger economic scale.” 

Reflecting on the lab’s partnership with industry members, Nadeau expressed gratitude. While most of the team’s work is gory — extracting internal organs and tissues for sampling — she said she can feel its impact, even in the early stages while picking up samples from wharves. 

“Our work wouldn’t be possible without local fishermen’s trust, participation and desire to learn more,” Nadeau said. “Many of them have been involved in the industry for years and provide a wealth of institutional insight.”