SANDBAR SHARKS: THE STOCK ASSESSMENT, AND BEYOND

 

Last week, I spent a few days down in Silver Spring, Maryland, attending the fall meeting of the National Marine Fisheries Service’s Highly Migratory Species Advisory Panel.  Sharks, and sandbar sharks in particular, were a major focus on the meeting’s last day.

Sandbars have been getting a lot of attention lately, because they have been one of the species most closely linked to shark depredation—that is, sharks stealing a recreational or commercial fisherman’s catch—not only in the South Atlantic and Gulf of Mexico, but all the way up into southern New England as well.

As a result, sandbar sharks have been one of the priority species for a stock assessment.  An assessment, dubbed SEDAR 101, as it is the 101^st assessment performed under the SouthEast Data, Assessment and Review process, began back in 2025, has been delayed a bit because of staff cuts at the Southeast Fisheries Science Center, and is expected to be completed and released sometime around the middle of next year.

It’s not clear what that assessment will say, and part of that uncertainty comes from the fact that determining what might be considered “normal” or, perhaps, “historical” sandbar shark abundance is proving to be a very difficult thing to do.

There is only one index, the Virginia Institute of Marine Science Longline Survey, that goes all the way back to the early 1970s, when the sandbar shark population had not yet been depleted by the commercial shark fishery.  It suggests that sandbar sharks were far more abundant in the 1970s and early 1980s than they are today, shows the population falling to near-time series lows in the late 1980s, then vacillating between such lows and somewhat higher levels ever since, without ever approaching the abundance levels of 45 years ago.

Other indices tell a somewhat different story. 

The Northeast Fisheries Science Center and Southeast Fisheries Science Center longline surveys didn’t begin until the latter half of the 1990s.  Both recorded their lowest abundance levels during their first few years of existence—from 1995 or 1996 through 2008 or so—then saw a steady and significant increase in abundance that peaked in the late 2010s or perhaps 2020, before going into a modest but noticeable decline ever since.  The Shark Research Fishery survey, which is tied into a special commercial permit that allows a limited number of fishermen—right now, only three boats opted to obtain the permit—to target and harvest a limited number of sandbar sharks each year, recorded its lowest value in its initial year of 2008, then increased steadily through 2012, at which point it declined a bit, held steady through 2020, increased to its highest level in 2024, and then registered a marked decline in 2025.

So the survey with the longest time series suggests that current sandbar shark abundance isn’t much higher today than it was 40 years ago, although it reached somewhat higher levels in intervening years and might be trending very modestly upwards today, while the other three surveys seem to suggest that sandbar shark abundance reached a nadir in the late 1990s and 2000s before increasing substantially through the early 2020s, at which point it suffered a modest decline.

The latter three surveys seem more in accord with lay observations, but the results of the Virginia Institute of Marine Sciences study can’t be ignored, and add some uncertainty to the assessment.  Because sandbar sharks probably haven’t been near their historical level of abundance for close to 50 years, people often forget how abundant they once were; one member of the Advisory Panel brought up the fact that anglers were now seeing sandbar sharks in western Long Island Sound, somewhere that, according to him, they were never seen before, a statement that forced me to say that we used to see sandbars off Greenwich, Connecticut—about as far west as you can go in the Sound without leaving New England—during the 1960s, and that they only disappeared some time after that.

The record of commercial shark landings, which extends back to 1950, might have cast some light on the question of past sandbar shark abundance, but it has uncertainty problems of its own.  Such landings were low into the 1980s, then spiked sharply in 1985, hit their peak a few years later, then fell sharply again in the early 1990s.  The problem was, until 1987, those landing weren’t identified as to species, and even though sandbar shark landings began to be separated out in ’87, some landings remained “unclassified” for about another 15 years, making it difficult, if not practically impossible, for biologists to tease out how much of the commercial landings consisted of sandbar sharks, and how much was composed of other shark species.

There is also some real uncertainty about the sandbar shark’s life history, which can impact the outcome of the assessment.  For example, we know that sandbar sharks don’t pup every year, but we don’t know whether a female produces pups every two years, or every three.  The answer to that question will make a meaningful difference in how many pups a female can produce over her lifetime which, in turn, will play a role in determining how much fishing pressure the stock will be able to bear.

We also don’t know how old sandbar sharks might get, another data point relevant to both lifetime pup production and the level of fishing mortality the species might be able to support.  Because sharks are difficult to age, the maximum age is often stated as a range; the Virginia Institute of Marine Sciences states that

“The species grows slowly and does not mature until it is about 25 years old.  Maximum age is unknown, but may exceed 50 years.”

However, that estimate appears to be an outlier on the high side, with the Florida Fish and Wildlife Conservation Commission’s description saying

“A slow-growing species, both sexes reach maturity around 12-13 years (about 6 feet) and are estimated to live 20+ years,”

while a paper produced for SEDAR in 2017 suggested that the maximum age for a sandbar shark is probably at least 31 years, and perhaps somewhat more.

Another problem with establishing maximum ages is that removing fish from a population can impact its age structure, by preventing fish from reaching the same age that they would in an unfished population.

So age, as well as pupping frequency, must be added to the uncertainties plaguing the sandbar shark stock assessment.

Faced with such substantial uncertainties, the stock assessment team is likely to conduct what’s called a “management strategy evaluation,” which can result in management procedures being established for the sandbar shark stock.  At the Advisory Panel meeting, the NMFS scientist heading the assessment team explained that a “robust management procedure” is effectively

“a weatherproof rulebook…

“A set of management rules that won’t lead to negative outcomes even if our data are highly uncertain, the climate shifts, or the fish (or fishermen) behave unexpectedly.

“Instead of trying to find the ‘perfect’ rule for a predictable world, a robust procedure is about finding a ‘safe’ rule for an unpredictable one.

“An empirical [management procedure] is based on data like an index of abundance that provides real time information about the stock.”

One of the possibilities is that, should the assessment recommend that sandbar sharks be removed from the prohibited list and a fishery reestablished, is that landings will be tied to some sort of index of abundance, with annual quotas rising, falling, or remaining the same based on the trends in that index.

Because many sharks share the same sort of uncertainties that plague the sandbar shark stock assessment, it is anticipated that future assessments of other shark species will follow the pattern—management strategy evaluation, management procedures, etc.—that are employed in the sandbar shark assessment.

Of course, what everyone wants to know is what NMFS will do once the sandbar shark assessment is completed.  NMFS probably wants to know the same thing.

One thing that a lot of people need to understand is that a stock assessment is just what its name suggests—it is an assessment of the health of the sandbar shark stock, which might include some projections of future abundance and recommend some possible management measures (e.g., reference points such as an overfishing limit and target fishing mortality rate or landings limit).  But the assessment is not, in and of itself, a fishery management plan; instead, it is a tool that NMFS can and will use when putting a fishery management plan in place.

The general public’s failure to understand the distinction between a stock assessment and a management plan came over loud and clear in the comments sent to SEDAR, where disgruntled fishermen, seeking to stem shark depredation, said things like

“There is an overpopulation of sandbar sharks in our waters from Ponce Inlet to Fort Pierce and I’m sure elsewhere and that’s where I normally go fishing from.  If it’s not myself it’s the person on either side of me reeling in a fish that gets eaten it’s about time to allow these fish to be harvested and thin down the numbers,”

and

“Too many sharks.  Need to cull them,”

while shark conservation advocates take the opposite tack, seemingly believe that the assessment is a proposal of some sort to resume sandbar shark harvest, and make comments such as

“This proposal is extremely devastating for the ocean and for people.  Sharks are vital for healthy marine ecosystems, so we must protect them not kill them and I am firmly opposed to any plan that increases shark fishing quotas,”

and

“Commercial shark long lining needs to remain banned as Atlantic sandbar sharks still had a 70% depletion in their populations in 2017.  They are still considered an endangered species and this will have dire consequences for the ecosystem.  An ecosystem without sharks will die and there will be no more fish to be able to fish up.”

It’s somewhat astounding how much the public gets wrong.  Not only is the stock assessment not a management plan, but without a completed assessment, it’s impossible to say whether sandbar sharks are rebuilding to historical levels of abundance, much less that they are “overpopulated,” “endangered,” in need of culling, or of being thinned down.

However, it is clear that NMFS intends to use the stock assessment, once it is finished, as part of its strategy to reduce shark depredation on the recreational and commercial fisheries.  At the Advisory Panel meeting, the agency made a presentation in which it noted that

“Public perception suggests the stock of sandbar shark has recovered from the overfished status determined in 2018.  Sandbar shark are one of the primary species associated with depredation events.”

Of course, public perception isn’t always right (recall how many comments sent in to SEDAR were from people who perceived the stock assessment to be a fishery management plan), and even if the sandbar shark is no longer deemed to be overfished, it’s population may still be—and probably is—a long way from fully rebuilt.

Despite all of the comments suggesting that the sandbar shark population has “exploded,”—24 such comments having been sent in to SEDAR alone—the sandbar shark’s life history renders explosive population growth impossible.  Think about it:  if it takes at least 12 years for a shark to mature and start producing pups of its own, then increasing sandbar shark abundance can only be a very slow process, because the spawning stock biomass can’t even start to grow until a dozen years after management measures are first adopted; until then, all the management measures are doing is preventing the spawning stock from declining as quickly as it had been before. 

Thus, NMFS is focusing much of its anti-depredation efforts on measures that focus on reducing depredation, rather than reducing shark abundance.  It is trying to determine where and when depredation is increasing, trying to determine why depredation may be increasing and, if it can get a handle on those factors, is also trying to determine whether the likelihood of shark depredation at certain times, in certain places, and perhaps in certain fisheries can be predicted, and whether, by predicting the likelihood of depredation, fishermen will be able to avoid its worst effects.

NMFS is also looking into the possibility of developing effective and practical technologies that will discourage depredation events.

And if the sandbar shark stock assessment (and future stock assessments for other species that engage in depredation, particularly bull sharks) indicate that it can be done without leading to overfishing and/or an overfished stock, NMFS will look into the possible solution that so many in the angling community suggest—increasing shark landings and so reducing shark abundance.

But that isn’t as easy an answer as some would like to believe.  Even if SEDAR 101 finds that sandbar sharks are no longer overfished and well on their way toward recovery (the current target recovery date is 2070, still 44 years away), that they can safely be removed from the prohibited species list, and that the stock can support some level of commercial and/or recreational fishing, relaxed regulations are not likely to lead to a substantial reduction in the sandbar shark population, nor are they, in and of themselves, likely to lead to a significant reduction in shark depredation.

That’s because relaxed regulations aren’t likely to lead to a significantly larger number of sandbar shark removals.  One thing that became very clear at the Advisory Panel meeting was that commercial shark fishermen are already having trouble finding markets for the sharks that they catch; they aren’t coming close to catching the entire commercial quota.  Thus, unless fishermen can find a way to open new markets, they will have little interest in an increased sandbar shark quota that only provides them with access to fish that they will be unable to sell.

As far as the recreational side goes, I noted at the meeting that even back in the 1970s and ‘80s, when there were neither size nor bag limits for sandbar sharks, it was very unusual for an angler to retain and eat them; their flesh was edible, but not prized, and the sandbar shark’s tough, knife-dulling skin made gutting and cutting one up almost more trouble than the meat was worth.  So allowing anglers to take sandbar sharks home probably won’t lead to significantly increased landings.  And the other source of recreational removals, tournament entries, are also unlikely to come into play, for if the sharks entered aren’t kept for food, and instead end up carted off to the town dump, public backlash is likely to be substantial.  We saw that in Florida a few years ago, when a kill tournament largely targeting bull sharks resulted in significant public outrage, and even threats of physical violence aimed at its organizers (after that session of the meeting ended, another Advisory Panel member walked over to me, told me that he was one of the people who organized the Florida tournament, and acknowledged the public outrage), while this summer, there were also much more measured expressions of discontent when the Alabama Deep Sea Fishing Rodeo decided to again award prizes for the largest sharks entered.

So, where does that put the sandbar shark, and where is NMFS likely to go with its efforts to reduce shark depredation?

The sandbar shark stock assessment should be completed sometime next summer, and assuming that it passes peer review—not a given for an assessment containing a lot of unknowns and perhaps an untested and potentially controversial management strategy evaluation—it will guide NMFS’ management efforts.  The stock assessment MIGHT find that the sandbar shark stock is no longer overfished, and that it might be safely removed from the prohibited species list, but that is not guaranteed. 

Depending on what level of abundance is eventually used as a baseline for a healthy biomass, the assessment might find that the stock is still overfished, no longer overfished but with a lot of rebuilding left to do, well on its way toward rebuilding or—perhaps the least likely—fully rebuilt.

And depending on that finding, NMFS might change commercial and/or recreational regulations regarding sandbar shark landings, perhaps partly in the hopes that higher landings might reduce depredation.

But right now, all of those things lie ahead of us.

Right now, we can only wait and watch as SEDAR develops its approach to assessing the sandbar shark stock, an approach that might be used to assess other shark stocks in the future.