Some 50 different species of this
most famous of marine predators regularly patrol the waters of coastal New
England. Globally, shark numbers are dropping, but scientists say the news here
is good—unless you’re a seal on Cape Cod.
Most people are familiar with one
species of shark: the misunderstood great white, made infamous by the movie Jaws and
the Discovery Channel’s Shark Week. But more than 500 species of sharks
ply the oceans of the world, and about 50 species can be found at one time or
another along the East Coast, from the modest smooth dogfish to the massive
basking shark. Many of them are studied by a handful of University of Rhode
Island alumni and faculty—who tell a very different story about sharks than is
conveyed by the popular media.
Unless you’re a fisherman or boater
who spends considerable time in offshore waters, it’s unlikely that you’ll ever
see a shark in southern New England, says Nancy Kohler, along
with Lisa Natanson and Camilla McCandless. The three study
the life history of sharks in the Atlantic Ocean and Gulf of Mexico for the
National Marine Fisheries Service’s Apex Predator Program, based right next
door to the URI Narragansett Bay Campus. They also conduct coastal surveys to monitor
shark abundance, and collect biological data about sharks captured at
recreational fishing tournaments.
They ticked off a long list of
sharks that spend at least part of the year in the area: blue, mako, common
thresher, sand tiger, smooth and spiny dogfish, basking, great white,
porbeagle, and occasionally tiger, hammerhead and sandbar sharks. But the species
most likely to be caught by fishermen in offshore Rhode Island waters is the
blue.
“Blue sharks use different parts of
the Atlantic for different parts of their life history,” explains Kohler, who
studied the species for her doctoral dissertation. “This area is mostly a
mating ground for them, which is why many of the larger sharks that fishermen
catch are adult males. They pup on the other side of the Atlantic.”
One result of Kohler’s long-term
tagging study of the species is a map of the impressive migrations they
undertake—they travel through almost every part of the Atlantic Ocean. She says
blues might, for instance, be tagged off New England and recaptured south of
the equator, and they often return to the exact same place in local waters year
after year.
Fishermen also catch a great many
spiny dogfish, though few fishermen are happy when they do. The four- to
five-foot sharks are often reeled in by recreational fishermen targeting cod
and other groundfish. While there is little market for them in the U.S.,
Natanson said there is a regional commercial fishery for them to meet the
demand for fish and chips in Europe.
Natanson, who recently started a
study of the reproduction of dogfish, says spiny dogfish have a unique
distinction among the sharks of the world. “They’re pretty small in the world
of sharks,” she says, “but their two-year gestation is the longest of all the
shark species.” That doesn’t mean they are necessarily slower to reproduce than
other sharks, however. “Most sharks have a two-year reproductive cycle—they’re
pregnant for one year and then they rest for one year,” she explains.
While dogfish are the most likely
shark species to be captured close to shore and in lower Narragansett Bay, they
aren’t the only ones. McCandless says commercial fishermen using fish traps in
the bay sometimes catch small sand tigers and even small white sharks, and
recent evidence suggests that sand tigers are regular visitors to Rhode
Island’s coastal waters.
“We currently survey shark nursery
habitat along much of the U.S. Atlantic coast and have plans to look at Rhode
Island coastal waters for this purpose, and Narragansett Bay is an obvious fit
for that study,” McCandless says. “We’ve done some exploratory sets in the Bay,
and we’ve primarily caught dogfish and skates. We haven’t caught any sand
tigers yet, but we know they come up here in the spring time, and they have
been caught in fish traps in the Bay.”
One of the most charismatic sharks
to visit southern New England waters is the mako, a species prized by fishermen
and one that URI Professor Bradley Wetherbee has studied for many years. He and
colleagues from Nova Southeastern University have tagged more makos in the
Atlantic than any other scientists. Their research is aimed at learning about
the health of mako populations, the migratory routes they travel, and the
locations of the preferred feeding grounds for what he calls the “fighter jets
of the shark world” for their swimming abilities.
He tracked one mako on a year-long,6,500-mile migration in 2015 and 2016, but it was caught and killed a short
time later by commercial fishermen off the coast of North Carolina. Sadly, it’s
not an uncommon occurrence. More than a third of the more than 50 mako sharks
he has tagged have been killed by fishermen.
Wetherbee doesn’t object to shark
fishing. In fact, his research is aimed at collecting information about the animals
so they can be better managed and available for sustainable harvest for many
years to come. He just hopes that any fisherman who catches a shark with a
satellite tracking tag on its fin will release the shark back into the water
unharmed.
The shark species that has received
the most media attention in the region lately has been the great white, because
their numbers have increased in recent years as they feed on the growing number
of gray seals that breed on Cape Cod beaches. And caught up in the media frenzy
has been Greg
He has cataloged 258 great whitesharks in southern New England since 2014, a number he says rivals other
hotspots around the world where the species has been intensively studied. He is
trying to get a sense for the total size of the population, what they’re doing
while they’re here, and where they go when they leave the area—both to help
conserve the species and to address public concerns.
“Our approach has been that the
more we know about its population size and where it spends its time, the better
equipped we’ll be to advise beach managers to enhance public safety,” Skomal
says. “The public is worried, but they shouldn’t be. Attacks happen so
infrequently. The probability is so low that their bigger concerns should be
rip tides and car accidents.
“Many people are also fascinated by
them, though,” he adds. “People come to the beaches hoping to see one. It’s
been an eye-opening experience for me. I see a lot of positives coming from
it.”
While most people are fearful of sharks, Wetherbee says
sharks have much more to fear from people than people have reason to fear
sharks. An estimated 70 million sharks are killed each year by commercial and
recreational fishermen—mostly to meet the demand in China for shark fin
soup—and there is concern that the rate is unsustainable.
Skomal said the greatest concern
for global shark conservation is in countries far from the United States where
harvest levels are high and there is little or no fishery management. “You
really have to look at where it’s happening and what species,” he says. “If
most of the harvest is in a certain region, then those sharks are in serious
trouble. There is so much diversity in the shark world, though. Some species
are prone to over-exploitation and others can be harvested sustainably.”
Sharks in U.S. waters, however, are being managed well, the
scientists said, and the data suggest an optimistic outlook.
“The indexes are going up,
indicators like our coastal survey have shown a steady increase, and even the
shark fishing tournaments are regulated,” says Kohler. “I’m not seeing the doom
and gloom here that we hear about elsewhere.”
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