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Commercial Fisheries News
Volume 35 Number 12
August 2008
Fleet helps assess yellowtail in Closed Area II
NEW BEDFORD, MA – Five commercial fishing vessels from this top-ranking port in the nation spent 10 days in June working on Georges Bank with researchers in a massive undertaking to obtain an independent estimate of yellowtail flounder abundance in the southern half of Closed Area II, which is part of the scallop fleet’s rotational access-area program.
Participating vessels included: Tony Pereira’s Blue Seas II; Tony Borges’ Sao Paulo; Carlos Camarao’s Virginia Sands; Tony Santos’ T-Luis; and Rodi and Rodney Avila’s Trident.
The teams tagged close to 72,000 yellowtail in five days – two days faster than planned – and then made separate randomly selected tows over the following three days to see how many of the tagged fish would be recaptured.
The project, the results of which helped to confirm the findings of recent conventional stock assessments, was deemed an enormous success by all involved. And, according to researchers, that was largely due to industry’s direct involvement.
“The scale of this experiment has never been tried before,” said Steve Cadrin, a National Marine Fisheries Service (NMFS) scientist who serves as director of the Cooperative Marine Education and Research (CMER) Program at the University of Massachusetts (UMass) Dartmouth.
“The fishermen were amazing. We couldn’t have done it without them,” he said.
Yellowtail estimate
By calculating the ratio of fish tagged to tagged-fish recaptured, researchers estimated that roughly 20 million individual age-two and older yellowtail were present in that southern half of Closed Area II.
That population represents somewhere between 20% to 30% of the total Georges Bank yellowtail resource, which is consistent with what traditional stock assessments have been finding over the past couple of years, said Cadrin, who also is a faculty member at the UMass School for Marine Science and Technology (SMAST).
Jessica Melgey, a student of Cadrin’s who developed the mark-recapture experiment as her thesis project, said the research team’s abundance estimate would change slightly “as we do editing and auditing of the data.”
And, she stressed, “We did this to supplement the stock assessment. It can’t stand on its own.”
However, Cadrin, Melgey, and involved fishermen all agree that this supplemental look at yellowtail abundance in what is considered to be a yellowtail haven was invaluable.
“It gave us a much clearer picture of what was in there than we had before,” said Melgey.
Industry’s view
Rodney Avila of the Trident typically stays ashore these days while his son Rodi runs the boat.
But he wasn’t staying ashore for the yellowtail project. He wanted to see for himself what was going on with yellowtail in the closed area.
“I was very excited about it,” he said.
Avila was working on familiar ground. The Trident was assigned to a grid in the southwest corner of the area, which is where Avila himself used to fish.
“I had at least half of my tows in that grid,” he said.
Avila took his old logs along on the trip, compiled during the days when loran A and paper plotters were the norm. On the steam out, he crunched numbers, made conversions, and ended up with modern-day comparisons to his former fishing trips.
As it turned out, Avila was extremely pleased with what he saw during the June 2-11 mark-recapture experiment.
“To me it was like what it was years ago,” he said. “What I really liked about it most was the number of different size fish we saw. We saw all the different year classes. I thought it was a great sign. It was good to see some recruitment. To me, that was the exciting part.”
It wasn’t just yellowtail the boats were seeing. According to Avila, his boat hauled up barndoor skates, a few halibut, and numerous other species, “from tiny to huge,” in addition to scallops.
“I saw a lot of big scallops,” he said.
Assessment controversy
The last time groundfish fishermen had a good crack at catching yellowtail in Closed Area II was in 2004 during a special access program (SAP).
In many ways, the SAP was a disaster. It opened on June 1 and, almost immediately, the market was flooded with tens of thousands of pounds of yellowtail, most of which were in poor condition – too soft to make good fillets – and prices were miserable, crashing to as low as 13 cents per pound.
Since then, stock assessments for the Georges Bank yellowtail flounder resource have been controversial. The assessments are conducted jointly with Canada through the Transboundary Resource Assessment Committee (TRAC).
For yellowtail, the TRAC used two different assessment models. The first was the “base case” model, which scientists now believe tended to overestimate stock size. The second was the “major change” model, which produced substantially lower biomass estimates.
As a result, industry members have questioned the yellowtail assessments coming out of the TRAC, along with the resulting US/Canada quota shares.
Estimates line up
Given this controversy, Cadrin and Melgey saw an opportunity to conduct an independent experiment.
“We were wondering, ‘Why are we getting such different information from two very different models?’ So we said, ‘Maybe the closed area is affecting the population dynamics,’” said Cadrin.
And so the experiment went forward. Numerous SMAST and NMFS scientists and students were part of the mark-recapture research team, and among them was NMFS’s Chris Legault, the US’s head yellowtail assessment biologist on the TRAC.
The team went into the scallop access area with high hopes, eager to discover hordes of yellowtail missed by traditional stock assessment surveys.
“That didn’t turn out to be the case,” said Cadrin. “There isn’t a secret stockpile of fish there.”
Instead, the industry/SMAST team’s results lined up fairly closely to other survey results.
Better information
During the 2007 TRAC, scientists, using the “major change” model, estimated the population of age-two and older Georges Bank yellowtail to be at 65 million individual fish.
“We found 20 million, which says that 30% of the Georges Bank yellowtail resource is in the southern half of Closed Area II,” said Cadrin.
TRAC scientists, using the “base case” model, calculated the population size at 100 million fish. The 20 million fish estimated during the industry/SMAST experiment represented 20% of the population under this particular scenario.
In either case, the mark-recapture experiment showed that 20% to 30% of the yellowtail resource was located in the scallop access portion of Closed Area II – pretty much in line with what the TRAC was finding.
“Our work didn’t support or refute either one of the models,” said Cadrin. “Both of those are reasonable estimates.”
Even though the team had hoped to find more fish, Cadrin said, “What we really wanted was a realistic estimate. These are valid results, and better information is always welcome.”
Results from the project will be forwarded to NMFS for use in future stock assessments, he said.
Industry’s knowledge
Even though the mark-recapture results won’t dramatically alter the course of fishery management, participants concluded nonetheless that it was a worthwhile project.
For starters, both Cadrin and Melgey said the strong partnership between industry and researchers benefited everyone.
Melgey, who sailed on the Blue Seas II, said she recognized how extraordinary it was for a graduate student to oversee a project of this magnitude.
“I felt really lucky to have so many resources at my disposal,” she said. “I appreciate so much all of the effort put in by all five captains and their crews. These are people who are out there all the time. They were an invaluable source of information. They knew where to catch the fish and when they’d be there.”
The experiment also reinforced the notion that surveying closed areas – in detail on a more regular basis – would give everyone more confidence in the numbers.
“Closed areas seem here to stay, and fishermen are going to want better information about what’s inside of them,” said Cadrin.
Melgey said she, too, couldn’t “overstate” the importance of surveying closed areas and added, “I think it’s a good idea to use cooperative surveys to do them.”
Rodney Avila agreed.
“I’d like to see the lightship done to get a better idea of what’s going on in there,” he said, referring to the Nantucket Lightship Closed Area, where yellowtail productivity appears to have declined significantly in recent years.
As for all those positive comments about industry’s invaluable role in the experiment, Avila took them in stride.
“When it comes to hard work, fishermen are good at it,” he said.
Janice M. Plante
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