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Commercial Fisheries News
Volume 35 Number 4
December 2007
Monkfish status reversed: Stock rebuilt
PLYMOUTH, MA – A new monkfish stock assessment has concluded that the resource in both the Northern and Southern Fishery Management Areas is not overfished and overfishing is not occurring.
The conclusion completely reverses the scientific community’s previous understanding about monkfish, which until now was considered to be overfished and in significant need of rebuilding.
“This is obviously a big turnaround from how we viewed this stock, so it’s important to note the uncertainty in the assessment,” said Jim Weinberg of the National Marine Fisheries Service’s (NMFS) Northeast Fisheries Science Center in Woods Hole, MA.
Weinberg presented the assessment results to the New England Fishery Management Council during its Sept. 18-20 meeting.
He explained that monkfish is the first species to be assessed by the science center’s new “Northeast Data-Poor Stocks Working Group.” Monkfish came first because under the current overfishing definition in the Monkfish Fishery Management Plan (FMP), the stock in both the north and south is considered to be significantly overfished, and the 10-year rebuilding deadline – May 2010 – is “fast approaching,” Weinberg said.
Monkfish is a “data-poor” stock because key biological factors such as growth, longevity, and natural mortality are all “poorly known,” and landings data and discard estimates prior to 1980 are so unreliable they weren’t even used in the new assessment.
Better approach
According to industry members, one of the most encouraging aspects of the new assessment is that scientists used a much wider variety of data than in the past.
Data types included: NMFS survey data; cooperative monkfish survey data gathered in 2001 and 2004 with industry; and commercial fishery data from vessel trip reports, dealer landings records, and onboard fishery observers.
Furthermore, this expanded information was plugged into a new “statistical catch at length” (SCALE) assessment model, which proved to be a better fit with monkfish.
In their report titled “Monkfish Assessment Summary for 2007,” scientists called the development of a new analytical model for monkfish “a significant advance.”
But they also warned, “The new assessment results are accompanied by substantial uncertainty and therefore need to be viewed with caution.”
Three independent scientists reviewed the results. They were John Annala of the Gulf of Maine Research Institute, who chaired the review panel, Robert Mohn of Canada, and Rafael Duarte of Portugal. Duarte is an expert on monkfish in Europe.
New reference points
Possibly the most significant outcome of the assessment was the recommendation of new biological reference points for monkfish.
The old biomass reference points hinge on a complicated calculation using a three-year running average of the science center’s fall survey and a kilogram per tow index. Under this old definition, the stock in both the north and the south are still considered to be overfished.
The new biomass reference points are based on a “revised yield-per-recruit analysis” using an updated natural mortality rate along with “results of a length-tuned model that incorporates multiple survey indices and catch data.”
Not that this calculation is any easier to understand, but the results are more straightforward and focus on total stock size levels.
The new biomass “threshold” – the lowest you can go without being overfished – is 65,200 metric tons (mt) in the north and 96,400 mt in the south. The new biomass “target” – the safer and more desirable number to be at – is 92,200 mt in the north and 122,500 mt in the south.
Total biomass estimates for 2006 turned out to be 118,700 mt in the north and 135,500 mt in the south, significantly above even the biomass target levels, which means neither stock is overfished under the new reference points.
Despite this extremely good news, NMFS is emphasizing that the new reference points do not automatically override the old ones. Those will stay in place until the New England and Mid-Atlantic Fishery Management Councils formally adopt – and NMFS approves – the new reference points through an amendment or framework adjustment to the monkfish FMP.
Fishing mortality
The assessment team did not recommend any change to the way fishing mortality is determined. However, scientists did update fishing mortality estimates.
The 2006 fishing mortality rates for the north and south respectively were estimated to be 0.09 and 0.12, both well below their respective overfishing thresholds of 0.31 in the north and 0.40 in the south. As a result of the updated values, overfishing is not occurring on either stock.
Good year classes
Weinberg also reported positive news regarding recruitment.
“Some good things happened here,” he said.
In the north, the stock produced three strong year classes in 1993, 1999, and 2001. In the south, the 2001 year class was considered to be “strong.”
Although the assessment team did not have time to develop a “complete projection model” to gauge how well the stock would continue to hold up in the future, it did have a chance to look ahead for at least a couple of years.
Using the target total allowable catch (TAC) limits of roughly 5,000 mt contained in Framework Adjustment 4 to the monkfish plan, Weinberg said the assessment team concluded that “the stock should continue to increase at a very low rate.”
Caution, caution
Even though monkfish biomass indices from science center surveys were approximately twice as high before 1980 than after, scientists were not able to use these higher numbers in the new SCALE model. The model “could only be applied to the period from 1980 to the present,” said scientists, in large part because landings data prior to 1980, a factor in the equation, were so unreliable.
“As such,” they warned, “the productivity of the resource may be higher than reflected in this assessment and thus, the possibility of attaining higher biomass levels in the future should not be discounted.”
In simpler terms, Weinberg said, “The biomass target and the biomass threshold maybe should be higher than what was proposed, so this is a source of uncertainty.”
Scientists furthermore expressed concern that the median and maximum sizes of monkfish in both the north and south have declined since the 1980s.
Work questioned
New England council member Mark Gibson of Rhode Island was totally taken aback by the assessment.
“I’m dumbfounded that the review panel and the assessors would put forward biomass targets and thresholds that are more liberal than what we had before and not rooted in population dynamics,” he said.
He also seriously challenged the decision to run the assessment using a time series that began in 1980 instead of back in the 1960s.
Gibson said he didn’t understand how those involved in the assessment “could advance these results to the management arena and completely reverse our view” about monkfish.
Weinberg explained that every one of Gibson’s concerns had been thoroughly hashed out during the week-long review meeting.
“Those are very legitimate points and they were all raised,” said Weinberg.
“At the end of the meeting, there was a long debate over whether to accept the assessment or not. It was a really tough call. But they (the review panelists) concluded that this was a big improvement and the model should be continued,” he explained.
A step forward
Massachusetts council member David Pierce was extremely pleased with the new assessment and said, “I’m thankful for the frankness that came out of that group.”
Although the discussion didn’t go anywhere, Pierce questioned why the council wouldn’t reconsider the TAC levels for monkfish in light of the new results.
“We’re totally rebuilt for both stocks,” he said.
Greg DiDomenico, speaking on behalf of the Monkfish Defense Fund, thanked NMFS and the science center for conducting the assessment.
“We’re extremely grateful to you for putting the effort and resources into this assessment, and for bringing in outside people to review it,” he said.
Janice M. Plante
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