IMPROVING ATLANTIC THRESHER SHARK MANAGEMENT

 

Although I knew they existed, I never thought much about thresher sharks—I should be more precise, and call them “common” thresher sharks, but as we never see any other species of thresher around here, no one does—until I was in my late teens and working in a tackle shop 50-some years ago, and one of our customers came in puffed up with pride and bragging that he caught a 400-pound thresher on his first trip off Montauk that season.

He was the first person I had ever known who had put one in the boat.

About the same time, I purchased a copy of Capt. Frank Mundus’ book, Sportfishing for Sharks, and noticed that in his chapter on threshers, Capt. Mundus noted that if you catch one, “you won’t be in a crowd,” because threshers were not all that easy to come by.

In the beginning of my shark fishing career, my experience with threshers was spotty, and more or less followed the Captain’s prediction.  We ran into very few.

We did hook a big one early—on the very first shark trip I took on my own boat out of Fire Island Inlet, in the summer of 1984, my first on Long Island—when I ran my 20-foot Sea Ox center console to an area near the Coimbra wreck, which was more than a 40-mile run once we got out of the bay.  From the point of view of both experience and equipment, we were woefully under-prepared, and were pretty well doomed from the moment the fish picked up the mackerel that was drifting on on one of my 30-pound rods.

One of my friends on the boat picked up the rod when the fish hit, but it didn’t do much for a while other than do deep circles around the boat, not taking much line but not giving back any either, while my friend’s back screamed out in pain (because yes, at the time, we were so poorly equipped that we didn’t even have a belt or a harness on board).  After a couple of hours had passed, the shark finally started coming up, making us think that we had hooked a decent mako that was about to go airborne, but what we finally saw was a thresher, which I now think was in the 300 to 400 pound range, that made two long, greyhounding jumps parallel to the surface of the sea, each one broadside to us and maybe four feet above the water, before ripping off a few hundred yards of line and coming out of the water again, this time in a pinwheeling jump that had the fish high in the air—something I’ve never seen a thresher do since—the top half of its body curving one way and its tail the other in a graceful arc reminiscent of the Chinese taijitu symbol used to depict yin and yang, before it fell back into the water and onto the line, breaking it and releasing my friend from any further suffering.

We saw a couple of free-jumping threshers over the next few years, but never had one pick up a bait.  Things sped up a little at the turn of the century, with one thresher boated and one tagged and released, but it wasn’t until 2018 or so that we started running into them often enough that Capt. Mundus’ comment no longer held true—by then, threshers were very much part of the crowd, and in any given season, might show up in our chum slick more often than the blue sharks or shortfin makos that used to make up much of our catch.

Anglers on my boat hooked three different threshers on one notable day in July, only eight or ten miles from shore in around 20 fathoms of water. 

And some of the threshers that we were hooking were big.

One of the Stony Brook University researchers I work with beat one that probably weighed a little over 300 pounds—about the same size as the fish described at the start of this post—in just 68 minutes last season; that shark was fitted with an acoustic tag and released.

A few years before, I had hooked what was roughly a 400-pounder on another 30-pound outfit intended for blue sharks and small makos, fought it for 3 ½ hours before the leader came up, and groaned when an untrained wireman couldn’t hang on, forcing me to spend another hour on the rod before the fight concluded.

And two years ago, during an early July coccolithophore bloom that tinted the water a strange shade of bright blue, I stood at the controls of my boat while another researcher fought a big fish that we never saw—but, given how it fought was almost certainly a thresher—for four hours and forty-five minutes on the same heavy outfit that defeated the 300-pound fish mentioned above in just over an hour, before the shark managed, in what would probably have been the closing minutes of the fight, to tail-wrap itself in the line above the 15-foot wire leader, chafe through the 80-pound monofilament, and set itself free.

I have no idea how large that latter fish was, but I know that the fight took the boat fully five miles from where we hooked up, and I know that after the line popped, the angler fell to the deck like someone who had been shot, and didn’t get up, or even move, for about a half-hour, at which point he got up, climbed down into the cabin, and laid on a bunk for the rest of the ride home.

So, we’re definitely seeing a lot more threshers in recent years, but what we don’t know is whether the increased number of encounters means that the fish are becoming more abundant or, for one reason or another, that they are merely becoming more catchable.

Thresher sharks primarily feed on small schooling fishes, including menhaden, other herrings, various mackerels, etc.  The argument can easily be made that, at least here on Long Island, we have had more of such small schooling species, particularly menhaden and chub mackerel, during the June-August period when most recreational shark fishing takes place, over the past decade than we have at any time in the previous 20 or 30 years, and that such smaller baitfish have concentrated threshers and made them more available to anglers, regardless of their overall abundance.

Although we are now halfway through October, and out of the typical window for recreational shark angling, threshers remain reasonably abundant just off Long Island’s beaches, as they join striped bass and giant bluefin tuna feeding on schools of menhaden migrating south and west along the shore.  But it’s hard to know what that says about thresher shark population trends.

The National Marine Fisheries Service released its Stock Assessment and Fishery Evaluation Report for Atlantic Highly Migratory Species, 2023-2024, earlier this year, and the information it provides about common thresher sharks is somewhat ambiguous.

From 2020 to 2024, the total dressed weight of commercially landed thresher sharks dropped sharply, from 62,485 to 39,265 pounds, although it was largely flat from 2022 through 2024.

The whole weight of threshers landed in the recreational shark fishery showed a far larger proportional drop between 2020, when anglers landed 54.1 metric tons, and 2024, when a mere 9.0 metric tons were landed.  However, the data does not show a smooth and predictable decline in the intervening years, with 32.8 metric tons landed in 2021 and 14.9 in 2022, before spiking back up to a series high of 55.7 metric tons in 2023.  In that context, the 9.0 metric tons landed in 2024 seems like an outlier, and not necessarily a sign of decline.

The number of threshers reported as retained by anglers in the Large Pelagics Survey, conducted between May and October of each year, showed a more orderly decline, from 24 in 2000 to 7 in 2024.  But when that data is read together with related data indicating that the number of threshers reported as released by anglers in the same survey increased from 17 in 2020 to 31 in 2024, there seems to be little convincing evidence of a significant change in thresher shark abundance.

But we just can’t know for certain, and with thresher sharks now the primary target of New England and upper mid-Atlantic anglers intending to retain a shark for food, data on thresher abundance is becoming more important if the stock is to be properly managed.

Yet no assessment of the thresher shark stock in the northwest Atlantic has ever been conducted.  Now, as NMFS is slowly completing its assessment of the sandbar shark stock, and developing new tools to assess data-limited shark populations, conducting an assessment of the thresher shark stock should be one of the top priorities of the agency’s highly migratory species assessment branch.

Even before that assessment is completed, NMFS should act to better ensure the long-term sustainability of the thresher shark fishery, by imposing a larger minimum size that would better accord with the species’ age at maturity. 

Right now, although the common thresher’s average fork length at maturity is 83 inches—just an inch shy of seven feet—the current recreational minimum size is a mere 54 inches, or four and a half feet, which means that many of the threshers landed have never had the opportunity to mature and to reproduce at least once.  A proposed rule to revise both commercial blacknose shark regulations and recreational Atlantic shark fishing management measures holds out at least the possibility that the minimum size for thresher sharks (along with blue and porbeagle sharks, which will be grouped together with the thresher) could be increased, perhaps to as large as 95 inches, in order to give members of the species an opportunity to mature and reproduce before being removed from the population.

We should learn whether NMFS opts to adopt such new management measures sometime in the next few months—almost certainly in the first half of 2027.

And we can only hope that NMFS decides to take action to properly manage the common thresher, both through a stock assessment and a realistic minimum size, now that the fishery for shortfin makos has been closed, and threshers are the only frequently-encountered large shark in the northeast that is valued as both a food and a sport fish, and so is thus being specifically targeted at a far higher rate than it has ever experienced before.