A
benchmark stock assessment, released in 2020, found that
“[The fishing mortality rate] in 2017 [the terminal year of
the stock assessment] (0.11) was below the Fthreshold (0.60) and Ftarget (0.22). In addition, the stock is above the current
fecundity target. The Atlantic
menhaden stock is not overfished and overfishing is not occurring. [emphasis in original]”
A
stock assessment update, released in 2022, found that stock status had not
changed, stating that
“The fishing mortality for the terminal year of 2021 was
below the [Ecological Reference Point] target ant threshold and the fecundity
was above the [Environmental Reference Point] target and threshold. Therefore, overfishing is not occurring and
the stock in not considered overfished.”
Unfortunately, in coming to those conclusions, the authors
of both stock assessments used an estimate of natural mortality (the fish that die
from causes that are not fishing-related) that was too high, which resulted in
an overestimate of population size and an overly optimistic evaluation of the
population’s status.
A new update to the single-species stock assessment was
recently completed (so recently that I received a copy in pdf form, as it has
not yet been posted to the Atlantic States Marine Fisheries Commission’s
website). It addresses the overestimate
of natural mortality, and the steps used to correct it, reporting that
“The only new change for this update assessment is the
inclusion of a new vector of natural mortality based on a revised analysis of
the historical tagging data that was completed by the M Working Group. The 2020 benchmark used the estimate of
[natural mortality] from Liljestrand et al.’s (2019) analysis of the tagging
data to scale the Lorenzen (1996) curve of [natural mortality]-at-age, assuming
that the [natural mortality] estimated from the tagging data represented the
[natural mortality] for age 1.5 menhaden,
based on the size of the tagged fish.
During the 2025 benchmark assessment process, Ault et al. (2023)
submitted a working paper to the Atlantic menhaden [stock assessment
subcommittee] and the Ecological Reference Points Work Group (ERP WG) that
re-analyzed the historical tagging data and produced an estimate of M=0.56,
significantly lower that the M=1.17 reported by Liljestrand et al. (2019).
“However, Ault had used a different subset of the data and a
different approach to handling key parameters, which made direct comparisons
with Liljestrand et al. (2019) difficult.
The [stock assessment subcommittee] formed a working group to review the
datasets and methods in consultation with the primary authors to determine the
best estimate of [natural mortality] for use in the Atlantic menhaden stock
assessment. The [M Working Group] and
[stock assessment subcommittee] determined that the main cause of the
difference in [natural mortality] estimates was the handling of the magnet
efficiency parameter [related to the detection of magnetic tags], which was
equivalent to the tag reporting rate in conventional tagging models. The [M Working Group] and [stock assessment
subcommittee] found that Liljestrand et al. (2019) had overestimated the magnet
efficiency rate in their analysis, but did not agree with the stepwise
estimation approach proposed by Ault et al. (2023) to estimate this
parameter. In the end, the [M Working
Group] and [stock assessment subcommittee] recommended a revised estimate of
M=0.92 from the tagging study, based on the corrected magnet efficiency rate
and updated effort and landings datasets, which was lower than the value used
in the 2020 benchmark, but higher than the value estimated by Ault et al.’s
(2023) method…”
To put that in simpler terms, the 2020 benchmark assessment assumed
that about 69% of the adult menhaden are removed from the population by natural causes each year, while the 2025 assessment update
assumes a natural mortality rate of about 60% (while rejecting the conclusion
of another team of scientists that only 43% of the population succumbs to
natural mortality each year).
The difference between 60% and 69% might not seem very
large, but it is large enough to cause the estimate of the Atlantic menhaden population
to drop substantially. A memorandum
prepared by the Atlantic Menhaden Technical Committee and Ecological Reference
Point Workgroup, addressed to the Atlantic Menhaden Management Board and dated
October 9, 2025 (which was attached to the copy of the 2025 stock assessment
update that I received), notes that
“the lower [natural mortality rate] used in 2025 resulted in
a lower biomass compared to the 2022 update.
The time-series average of age-1+ biomass for the 2025 update with the
lower [natural mortality rate] was 37% lower than the time-series average in
the 2022 update. In addition, the 2022
update showed a large increase at the end of the time-series that not present
at the end of the 2025 update.”
That 37% reduction, plus the absence of a large biomass increase near the end of the time series, was enough to change the status of the stock from one with a fishing mortality rate below the target level and a fecundity level above the target to one with a fishing mortality rate and a fecundity level that sits between target and threshold.
That’s a big change, but not catastrophic,
for while managers should always attempt to maintain both fishing mortality and
biomass/fecundity at or near target levels, the fact is that for most species,
most of the time, fishing mortality will often stray above target while biomass often remains below. Things only get truly serious if a stock becomes overfished or overfishing occurs.
So far, that is not the case for Atlantic menhaden, and the
2025 assessment update noted that
“Short-term projections at the current Total Allowable Catch
(TAC) of 233,550 [metric tons] were provided.
Under a constant TAC of 233,550 mt, [fishing mortality] will be between
[the fishing mortality target] and [the fishing mortality threshold], with a 4%
probability that [fishing mortality] will be above the [Ecological Reference
Points’ fishing mortality threshold] and a 100% probability that it will be
above the [fishing mortality target] in 2028.”
While that might not seem too dire, there are some important
facts that it leaves unsaid. One is
that, as noted in the October 9 memo,
“the 2021 biomass that was projected forward to inform the
2023-2025 TAC options was approximately 60% higher than the 2023 biomass, which
is informing the 2026-2028 TAC.”
So the Management Board is going to have far fewer fish to
work with when setting the overall TAC, as well as individual state quotas,
this time around.
As a result of the corrected, smaller population size, the 2025 assessment
update found that 2023 fecundity was just 71% percent of the target level and,
more significantly, just 105% of the fecundity threshold. So while the Atlantic menhaden stock might
not have been overfished in 2023, fecundity needs only fall a few more
percentage points, to anywhere below 100% of the threshold, for menhaden to
become overfished.
That should be setting off alarms at the Atlantic Menhaden
Management Board, and making it clear that maintaining status quo—in the form
of a 233,440 mt Total Allowable Catch—is neither a prudent nor a viable option.
For while the current TAC might not lead to overfishing, it could
very well lead to an overfished stock, which is not an acceptable outcome.
Thus, if the Management Board is to be a responsible steward
of the menhaden resource, it must make a substantial reduction in the menhaden
TAC for the years 2026-2028.
How large should that reduction be?
If we want to get fishing mortality back down to its target
level, the TAC must be cut by more than 50%.
The October 9 memo presents a number of options, built around the
likelihood of exceeding the TAC in the upcoming years. The most liberal of the options presented, a
110,000 mt TAC for the entire 2026-2028 period, that would carry a 60%
probability of exceeding the fishing mortality target, represents about a 52.5% reduction in TAC compared to the TAC currently in place (although the
reduction compared to 2024 landings would be less, as such landings were about
20% below the existing TAC).
A more prudent TAC, that would have just a 50% probability
of exceeding the target—and so represent a sort of mirror image to the usual
process of setting harvest at a level with a 50% probability of not
exceeding the mortality level needed to achieve management success—would cut
landings back to 108,450 mt, nearly a 54.5% reduction from the current level.
As a practical matter, the difference between a 54.5%
reduction and a 52.5% reduction is trivial, and hardly worth arguing
about. But we can be sure that the
findings of the 2025 stock assessment update, and the recommendations in the
October 5 memo, are going to set off an intense debate between the menhaden
industry and the folks who want to shut most of that industry down.
It is extremely likely--it is a virtual certainty--that the menhaden industry will howl
and complain that it can’t absorb a 50%-plus cut in harvest, and that the
Management Board should adopt a new TAC that is very close to the one now in
place. It might—or might not—be willing
to accept a 20% TAC reduction, given that the menhaden fishery only landed
about 80% of its quota last year, and a TAC of around 187,000 metric tons would
be larger than the TAC for 2013-2014, and about equal to the 187,880 mt TAC
that was in place for 2015-2016.
But that level of landings would almost certainly mean that the fishing mortality target would be exceeded, and when
managers go to the trouble of setting a target—essentially saying that,
ideally, “fishing mortality ought to go no higher than this,”—they do have an
obligation to the public to at least try to achieve that
goal. Each person might have a different
definition of “try,” but it’s probably fair to say that if you adopt management
measures that, more likely than not, will lead to a fishing mortality target
from being exceeded, you’re not really trying at all.
The menhaden fishing industry will be on shaky ground if
they argue for keeping the menhaden TAC at or near its current level, or
at or near current landings. Throughout
the debate over the proper level of, and methods used for, menhaden harvest,
the industry has regularly called for following the science, rather than giving
in to emotional arguments. Now that
we have the science telling us that menhaden fecundity was hovering just above the
threshold that denotes an overfished stock in 2023—it could conceivably have
slipped below that threshold since, although we lack the data to know if it has—and telling us that we need to cut the TAC by more than 50% to achieve the
target fishing mortality level, the industry has the choice of staying true to
its previous messaging, and going along with what the science appears to
demand—even if that means taking a serious economic hit—or suddenly saying that
the science isn’t the only consideration, and looking like hypocrites.
We can’t know for certain which course they’ll choose,
although “follow the money” is usually dependable advice.
On the other side of the table, we’ll undoubtedly see the
folks who worship at the menhaden's altar, and have regularly made
irrational and scientifically unsustainable calls for the elimination of the
menhaden reduction fishery, increase the volume of their yowling, and use the
2025 assessment update as an excuse to redouble their efforts, never seeming to
realize that a menhaden that dies in a pound net is just as dead, and has the
same impact on the stock as one that dies in a purse seine.
By focusing on eliminating a gear type instead of on
reducing the TAC, such persons will make it easier for the industry to prevail,
as they open the door to equally emotional arguments that the reduction industry is unjustly
targeted, that ending the reduction fishery would kill an economically important business in a
generally depressed area of the coast, and that closing that fishery would deny employment for
people—including many people of color—in a region that offers few viable
alternatives.
And it will be easy for the industry to argue that, even
with the population size revised downward, the menhaden stock is not in anywhere near as bad condition as the industry's opponents maintain.
The October 9 memo shows that menhaden landings—and, in particular, menhaden reduction landings, have been relatively stable since 2000. During that time, overall landings ranged between a low of 169.4 metric tons in 2013 to a high of 270.05 metric tons in 2001, with landings in 2023, the last year in the time series, coming in closer to the low end, at 181.75 metric tons.
Similarly, reduction landings ranged from a
low of 124.60 in 2020 (and 131.02 in 2013, the lowest non-COVID year) to a high
of 233.56 in 2001, with landings in the last three years of the time series,
2021, 2022, and 2023, coming in near time-series lows, at 136.69, 136.70, and
131.80 metric tons, respectively, even though the ,menhaden TAC has been increasing in recent years.
At the same time, the 2025 assessment update revealed that
current spawning stock biomass is higher than it has been for most of this
century, that the current fishing mortality rate is near the middle of its
range for the past 30 years, and that current recruitment is better than it
has been in most years since 1990.
However, it also indicates that both age-1+ biomass and fecundity are
either at, or not far from 30-year lows.
So, after discounting the demands from both stakeholder
extremes, what should the Management Board do when it meets on October 28?
The need to cut the TAC—sharply—is clear. Ideally, the 2026-2028 TAC should be reduced
to no more than 108,450 metric tons, although its unlikely the Management Board
will have the appetite to get that done over the course of a single year. In the real world, some sort of phase-in is
likely, but so long as there is a fixed schedule to get the TAC down to that
level over the course of a few years—ideally by 2028—no one will have too much
reason to complain.
Of course, the industry almost certainly will complain anyway. They’ll argue that a cut of more than 50%,
even if phased in over the course of three years, is too sudden and extreme for
them to bear. But the fact is that the
TAC should never have reached 233,550 metric tons. It got that high only because the biologists
made a mistake, and adopted a natural mortality rate that was too high, and so skewed previous stock assessments.
No one was really to blame for that error—not the scientists doing the stock assessment, who relied on what they thought was accurate data; not the Management Board, who relied on the assessment when setting the TAC; and not the fishermen who relied on the Management Board to set the TAC at the proper level.. But blame isn’t the issue.
The simple fact is that the menhaden industry was killing more
menhaden than they should have been, and now that we know that to be true, the
Management Board needs to get landings down to a more sustainable level.
One might borrow a concept from civil law, and argue that
the menhaden fishery was “unjustly enriched” by the error in the stock
assessment and received a benefit, in the form of far more fish, than they were entitled to. If that had
happened in a financial context—if, for example, someone’s bank made an error
and credited their account with $100,000. instead of $1,000.00 because someone put a decimal point in the wrong place—the party who was unjustly enriched
would have to return all of the assets that they weren’t entitled to.
But no one is suggesting that the menhaden industry make pound-for-pound paybacks of the extra fish that they harvested as a result of the earlier stock assessments’ error.
No one
is suggesting that they make any sort of restitution at all.
But now that we know that the earlier natural mortality
estimate was wrong, it’s neither unreasonable nor unfair that the Management
Board reduce the TAC to what it should have been all along.
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