Most sharks eat fish.
And like any predator, while they are capable of successfully hunting
healthy prey, they are attracted to the easy kill, to prey that is sick,
wounded, disabled—or tethered by an angler’s line.
As fishery management efforts show some success, and depressed
populations of some shark species begin to rebuild, shark depredation—the term
used to describe sharks striking a fish already hooked on an angler’s line or
caught in a commercial fisherman’s gear—is becoming a bigger and bigger
issue. It seems that, while fishermen have
no compunctions about catching and keeping fish that constitute the sharks’
usual prey, they get very upset when the tables are turned and a shark snatches
a fish from an angler’s line.
“develop ways to improve coordination and communications
across the fisheries management community and shark research community to address
shark depredation,”
identify research priorities and funding opportunities related
to topics relevant to the depredation issue,
“develop recommended management strategies to address shark
depredation; and coordinate the development and distribution of educational
materials to help the fishing community minimize shark interactions including
through changed angler behavior and expectations. [original formatting omitted]”
The Act also calls for the development of
“Projects to better understand shark depredation, including identifying
what causes increases in shark depredation and determining how to best address
shark depredation.”
Although the SHARKED Act has yet to pass the Senate, and its
provisions have not yet been signed into law, it seems that a
biologist employed by the Bonefish and Tarpon Trust has been conducting his own
project to understand shark depredation in the Florida Keys and, at least with
respect to one important corner of Florida Bay, he may be coming up with some
interesting answers.
Dr. Jose Emilio Trujillo set about his task two years ago,
working with anglers and fishing guides in the region to gather their
experiences with shark depredation, focusing on the most popular recreational
species: snook, tarpon, red drum,
bonefish, and permit. He found that,
throughout the Keys, about 10% of hooked bonefish, permit, and tarpon fell
victim to shark depredation. But he also
found something else—in the popular fishing grounds near Flamingo, Florida, 31%
of hooked snook and 23% of hooked red drum were lost to depredating sharks.
While four shark species—great hammerheads, blacktips, bull
sharks, and lemon sharks—were responsible for the depredation events, it was
lemon sharks that snatched most of the snook and red drum lost in the Flamingo
area.
Not all lemon sharks engaged in that behavior. According
to an article in the South Florida SunSentinel, Dr. Trujillo found that
“there were two groups of lemon sharks using Flamingo—‘resident’
that were Flamingo homebodies and ‘transient’ who would often leave the area.
“About 28% of those sharks focused their time on known
fishing hot spots that anglers would use on a regular basis.
“Fishing boats show up at those hot spots about 8 a.m. The sharks tended to show up just before
that.
“One shark tracked for more than 100 days came ‘over and over’
to a specific hot spot.”
So for that particular group of lemon sharks, at least,
depredation might be a learned behavior.
But it may also be a behavior that has been forced on the
sharks as a result of changes to the ecosystem in the Flamingo region, where
sea grasses have experienced significant die-offs. As Dr. Trujillo observed,
“Changes in the seagrass basically resonate in the whole
community, in the whole ecosystem. And
we know that seagrass die-offs have resulted in declines in prey.”
It’s very possible that the lemon sharks around Flamingo
have turned to depredating anglers’ fish because their more usual prey has become
less abundant. Dr. Trujillo has pointed
to studies, conducted during the 1990s, which found that lemon sharks fed on
small fish typical of the seagrass ecosystem, such as pinfish, toadfish, and
mullet, and rarely preyed upon snook or red drum. But in his recent studies, he has found that
about 30% of the lemon sharks had been feeding, at least in part, on snook,
something that he characterized as “very odd.”
He noted that
“No study until now has reported lemon sharks eating large
prey like gamefish that are a high trophic level species. The fact that we are finding snook in their
diet is…not normal. That indicated that
they are obtaining this resource through a new way of hunting, which we believe
is depredation.”
A stock
assessment released in 2021 reported,
“Results suggest Lemon Shark stock abundance [off the
southeastern United States] has been relatively stable since the mid-1990s,
with some estimates of prior depletion.
Estimates of relative fishing mortality indicate earlier periods of
overfishing with a decrease in fishing mortality since the early 2000s.”
At the same time,
“Life history characteristics suggest the Lemon Shark is
vulnerable to exploitation. In recent
years, there is some evidence that Lemon Shark catch rates have declined and nursery
sites have been negatively impacted by anthropogenic pressures off the
southeastern USA. These factors have
increased conservation concerns and led to changes in fishery management. For example, the Florida Fish and Wildlife
Commission added Lemon Sharks to the prohibited species list in 2010,
preventing their harvest in Florida state waters. [citations omitted]”
Thus, the increased levels of depredation by lemon sharks
seems driven by a change in behavior rather than a change in lemon shark
abundance.
Still,
the knee-jerk reaction of many recreational fishermen to the depredation is to
call out for more sharks to be killed, in order to decrease the competition for
limited marine resources. I was
appointed to the National Marine Fisheries Service’s Highly Migratory Species
Advisory Panel in 2024, and in the four meetings I’ve attended so far, none
have passed without someone in the recreational fishing community complaining
about shark depredation, and calling for some sort of effort to reduce shark numbers.
The same sentiments exist in southwest Florida; the SunSentinel
article quotes a local angler named Collin Ross, who complained that
“You can’t get away from the sharks. They’re all over the place. It is a huge issue…
“You used to be able to fish without any type of issues, and
now you fish some areas and you have to leave immediately because of the
sharks.”
Mr. Ross admits that he doesn’t know why shark depredation
has increased.
“All we know is there are a lot more sharks in areas where
people are fishing. Why are they
congregating? Is there an
overpopulation? I don’t know.”
Yet, while he admits that he doesn’t know why depredation is
occurring, he seems to think that he knows how to address it.
“We’re hoping that the [Florida Fish and Wildlife Conservation
Commission] allows changes to federal law around lemon sharks, and then the
guides can take it into their own hands and they can cull sharks as they see
fit.”
“Cull sharks.” Just
kill them off because, I suppose, it is always easier to blame the sharks for
the problem, and start killing them, than it is to address the real issue of
seagrass loss. One United States
Geological Survey publication suggests that restoring the seagrass of the Florida
Bay and Everglades watersheds would take about 20 years and cost approximately
7.8 billion dollars, and would not only require restoring fresh water flows into
Florida Bay, but also ensuring that the water flowing in doesn’t carry pollutants
that would increase the Bay’s nutrient load, and actually make the current
problems worse.
Killing sharks is certainly quicker and cheaper than that, so
it has many supporters, even if it is the wrong response to the problem.
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