WILD SIDE
PHOTO BY DOUGLAS H. ADAMS SHARK TRUTHS
BY CAMILLE S. YATES
It’s no bull that sharks swim in the Indian River Lagoon.
Treasure Coast scientists have discovered that the lagoon
is an important nursery habitat for bull sharks. Douglas
H. Adams, a scientist with Florida Fish and Wildlife Research
Institute, emphasizes that there have been no known attacks
of bull sharks in the lagoon and that chances of being
attacked are remote as long as safety precautions
are followed.
Adams has been studying the life histories of fish in the
lagoon for over 15 years. Through his work and work from
other scientists, too, interesting information has surfaced
about sharks in the lagoon. “We have found that in spring
and early summer, pregnant female bull sharks enter the
lagoon via the inlets to give birth to their young, known as
pups,” said Adams. “Each pregnant female can carry a litter
of up to 13 pups, and each pup is approximately 24 to 32
inches long at birth. Juvenile bull sharks can utilize the
lagoon for several years.”
Bull Sharks (Carcharinus leucas) are grey with an off-white
underside. Young bull sharks can be mistaken for another
species, the
black tip shark.
The bull shark
gets its name
from its stout
appearance and
pugnacious reputation.
It has a
blunt nose, stout
body and no
dorsal ridge. It is
a slow swimmer,
can breathe
while at rest,
and can grow to
about ten feet. It
is the only shark
that can survive
in either fresh or
salt water. Bull
sharks are world class travelers, having been found 2,000
miles inland, with sightings in the Amazon River, Lake
Nicaragua and Guatemala's Lake Yzabal, but their favorite
hangouts are in shallow
waters along the continental
shelves.
Bony fishes make up the vast majority of the bull shark's
diet. They commonly feed on mullet, tarpon, catfishes, menhaden,
gar, snook, jacks, mackerel, snappers, and other
schooling fish. Scientists have also found sea turtles, dolphins,
crabs, shrimp, sea birds, squid, and dogs in the stomach
of bull sharks.
Adams says bull sharks can be found in a wide array of
marine and estuarine habitat types and swim in most areas
of the Indian River Lagoon. Other shark species also use the
lagoon near and within inlets such as the blacktip shark,
spinner shark, tiger shark, nurse shark,
and bonnethead shark. A local shark fisherman,
Gary Williams, caught a sharpnosed
shark 7 miles south of the Fort
Pierce Inlet. Williams has also caught
large bull sharks in the lagoon. “Between
myself, my son, John, and our fishing
buddy, Eric Lewis, we have caught bull
sharks from 6 feet to 11 feet in length in
the lagoon and the 11' female had an estimated
weight of 500 pounds,” he says.
As part of ongoing research, the
University of Central Florida Sea Turtle
Research Group nets and studies juvenile
green turtles in the lagoon. Through their
studies, Dr. Llew Ehrhart has noticed an
increase in the capture of bull sharks and rays over the last
few years. Interestingly, in 2001, the group caught two tiger
sharks (one approximately 7.5 feet and the other 6.5 feet) in
their nets. This was the first recorded instance of tiger sharks
being found in the lagoon. It is known that tiger sharks are a
major sea turtle predator.
Although sharks have drawn great apprehension and fear
among people since antiquity, a person is more likely to be
hit on the head with a coconut while walking down the
beach than being attacked by a shark. “While there have
been interactions between bull sharks and humans elsewhere
in Florida, there have been no documented bull shark attacks
on humans within the lagoon,” Adams says. “The key to
safety is to respect sharks and to reduce any chances of an
encounter by knowing their behavior, where they’re most
likely to be, and knowing the cues that set them off.”
Here are some tips to prevent being
mistaken for shark food:
1. Avoid swimming near river mouths or
other estuaries with muddy or cloudy
waters where bull sharks are known
to occur.
2. Do not swim near schools of fish in
inshore areas. These schools are often
pursued by large predators.
3. Be cautious if spearfishing. Bull sharks
are known to approach spearfishermen
carrying their catch.
4. Do not duplicate the practices of some
television “adventurers” who flagrantly disregard
common sense while swimming
around sharks underwater.
82
Bull shark
no stranger
to lagoon
This bull shark, left, was caught
in the Indian River by biologist
Douglas Adams and later
measured. These bull shark,
below, swim in the Indian River
near the Fort Pierce Marina.
PHOTO BY GARY WILLIAMS