In a decision being watched closely by Cape Cod fishermen, the U.S. is rejecting a proposal that calls for a reduction in the total catch limit of the Western Atlantic bluefin tuna.

In current negotiations among member countries of the International Commission for the Conservation of Atlantic Tunas (ICCAT), many call for a 24-percent reduction in the catch, from 2,350 metric tons to 1,785 metric tons.

The dispute pits the U.S. against other countries. It also pits fishermen, who see waters teeming with tuna, against scientists, who warn of imminent danger to the stocks.

ICCAT scientists warn that the current quota creates a 94-percent chance of overfishing for the historically threatened bluefin. But without support from the U.S., a consensus will not be reached, and the current quota will remain in place, raising the strong chance of overfishing for 2021.

Those favoring the reduction say it’s for business, not just environmental reasons. “Bluefin tuna has been the poster child for overfishing, and they are finally starting to regain their reputation in the market,” said Shana Miller, senior officer at the Ocean Foundation. “This would just undermine all of that progress and send it back to the red zone as one of the most irresponsibly managed stocks on the planet.”

This year’s proposal to lower the quota comes after three years of raised quotas in response to growth in the stock. When the quota was first increased in 2017, ICCAT scientists warned that in 2020 it would have to be reduced again.

“ICCAT increased the quota with that knowledge in mind,” said Miller. “Yet here we are three years later and it’s like the U.S. has amnesia.”

This year, in an unprecedented move, the U.S. is questioning the validity of the science in the stock assessment and calling for an entirely new assessment in 2021.

According to written statements to ICCAT, the U.S. — represented by a team of NOAA officers led by Andrew Lawler, a recent Trump political appointee — claims new data reveal unrecognized abundance.

The U.S. points to 2019 and 2020 data that haven’t been included in the latest assessment from the small bluefin tuna recreational fishery, and says flaws in the indices used to assess the data are a reason to challenge the science.

ICCAT scientists have agreed to look at the indices and see what improvements can be made, but according to officials advocating a reduced quota, that does not change the scientific advice that included the new quota of 1,785 metric tons.

Grantly Galland, International Fisheries Officer at Pew Charitable Trusts worries the push to question the assessment is a blame the messenger phenomenon, born of the industry’s frustration with the findings, and, he said, “the government is buying into that.” The data being questioned is, he said, “an American data set that has been used for 22 years.”

Galland added, “I am fully willing to admit that they may be seeing more bluefin than they have been seeing in recent times, and in another 2-3 years those fish will become part of the fishery, part of the assessment, and therefore the catch limits can go right back up. “But what we know now is that the best available science from this year says that the limit needs to come down.”

Still, many in the industry share the view that the science is inaccurate. This year, what Cape Cod tuna fishermen saw on the water paints an entirely different picture than the one the stock assessments do.

“I’ve had 35 very successful years of tuna fishing, but this year there were so many bluefin east of Chatham that the fishermen I work with didn’t even need a spotter pilot,” said Norman St. Pierre, longtime spotter pilot out of Chatham.

Scientists and conservationists warn against taking the evidence on the water as the full truth.

“That sort of anecdotal evidence of folks out on boats seeing a lot of bluefin is just not how we do stock assessment science,” said Galland. “The scientists are always trying to make sure they are right, and, if they are not sure, they are not going to offer advice that is detrimental to the fishermen.”

Another factor contributing to the difference between anecdotal evidence from fishermen and stock assessments from scientists is that there are two Atlantic bluefin tuna stocks, an Eastern and a Western, spawning in the Mediterranean and the Gulf of Mexico, respectively.

Cape Cod fishermen are controlled by the Western quota, but because the bluefin tuna is a highly migratory species, many of the fish that they see and catch here are coming from the much larger Eastern body of fish. The quota for the Eastern Atlantic is 36,000 metric tons, 15 times the size of the Western Atlantic quota.

According to the 2017 stock assessment conducted by ICCAT scientists, the Western Atlantic bluefin tuna biomass is at approximately 18 percent of its 1950 population. But with a massive Eastern stock swimming in American waters, the overfishing and depletion of the Western Atlantic bluefin tuna is not noticeable on the water.

And though the species co-mingle, and can be told apart only by genetics, maintaining the Western stock is incredibly important for the U.S. commercial fishery.

“We don’t want to rely on fish coming from the East because then the decisions are taken out of our hands,” explained Galland. “If we put our Western population to the point of being threatened, then we are relying on folks in the East to make good decisions. That’s why it really is important to negotiate over a couple hundred tons in the West because the stock is so vulnerable to overfishing in the long run.”

And in the context of climate change, the Western stock that spawns in the warmer Gulf of Mexico is much more tolerant of warmer temperatures. “That is incredibly important to preserve,” said Miller.

With at least a week left of email negotiations, the 2021 bluefin tuna quota remains uncertain. If the U.S. remains steadfast in its opposition to a lower quota, then a rollover will occur for 2021. Though it would be a win for the industry at large, it might set up further reductions in 2022 and 2023.

What it boils down to, Galland said, is whether science will shape management or we’ll see “a return to the old days of putting short term political decisions ahead of long-term sustainability.”