There are about forty species of sharks that occur
in Hawaiian waters, ranging in size from the deep-water pygmy shark
(about 8 inches) to the whale shark (up to 50 feet or more).
About eight species are somewhat common in nearshore waters. The most frequently
encountered are the whitetip reef, sandbar, scalloped hammerhead, and occasionally
These inshore species are top-level carnivores, feeding primariy on fishes.
Their roles in reef ecosystems are not fully understood, though they may keep
fish population sizes in check, and remove sick and injured fish, leaving the
healthiest to survive and reproduce.
Sharks have extremely well-developed sensory capabilities. They can detect
sounds and smells from prey at great distances (up to a mile or more, depending
on water conditions). Their eyesight is good, but depends greatly on water
As sharks approach their prey, they can detect the faint electric fields given
off by all living organisms. Receptors on their snouts, known as ampullae of
Lorenzini, allow sharks to locate their prey without seeing it.
Using these and other senses, sharks can find prey at dusk, night, and dawn,
which is when some inshore species are generally believed to feed.
Sharks are very much attuned to their environment. They know when people are
in the water long before people are aware of them. Encounters between sharks
and people are infrequent, and most inshore species pose little threat to humans.
Although any shark may be potentially dangerous, especially if provoked, it
is believed that only a few species of Hawaiian sharks have been responsible
for biting people. However, many inshore species are difficult to distinguish
from each other, and positive identification is often not made.
In cases where the offending shark can be identified, tiger sharks top the
list. A tiger shark is easily recognized by its blunt snout and the vertical
bars on its sides. Hammerheads are also easy to identify, and have been implicated
in a few cases where they may have been provoked.
Tigers are considered the most dangerous sharks in Hawaiian waters. White sharks,
which are also very dangerous, are rarely seen in Hawaii. Because of their
size and feeding habits, tigers occupy the very top niche in inshore feeding
For years tiger sharks were believed to be territorial in nature. Individuals
were thought to remain for the most part in a fairly limited area. Recent evidence
suggests this is not the case. Tiger sharks have been found to navigate between
the main Hawaiian islands, and thus appear to occupy home ranges much larger
than had been previously suspected.
Tiger sharks are often attracted to stream mouths after heavy rains, when upland
fishes and other animals are swept out to sea. They can easily locate prey
in such murky waters. Tigers are also attracted to waters frequented by fishing
boats, which often trail fish remains and blood.
Of all the inshore species, tiger sharks have the most widely varied diet.
They eat fish, lobsters, birds, turtles, dead animals, even garbage, and may
feed whenever a food source is present.
It’s not known why tiger sharks sometimes bite humans. The idea that
they mistake a person for a natural prey item, such as a turtle, is not supported
by any evidence. The shark may be trying to determine if a person is a potential
prey item, it may come across a person while in a feeding “mode,” or
perhaps there is some other explanation.
Incidents of sharks biting people in Hawaiian waters are very rare,
occurring on average at a rate of about three or four per year.
Fatal shark bites are
extremely rare, especially considering the number of people in Hawaii’s
People who enter the water need to recognize that there are hidden
dangers. A number of marine animals can cause serious injury to
people, and sharks are
just one example. Entering the ocean should be considered a “wilderness
experience,” where people are visitors in a world that belongs to the
The risk of injury caused by sharks is extremely small, but it
is a risk accepted by anyone who enters the shark’s world.
By learning more about sharks, using common sense, and observing
the following safety tips, the risk may be
Ten Safety Tips to Reduce the Risk of Shark
1. Swim, surf, or dive with other people, and don’t move
too far away from assistance.
2. Stay out of the water at dawn, dusk, and night, when some species of sharks
may move inshore to feed.
3. Do not enter the water if you have open wounds or are bleeding in any way.
Sharks can detect blood and body fluids in extremely small concentrations.
4. Avoid murky waters, harbor entrances, and areas near stream mouths (especially
after heavy rains), channels, or steep dropoffs. These types of waters are
known to be frequented by sharks.
5. Do not wear high-contrast clothing or shiny jewelry. Sharks see contrast
6. Refrain from excesive splashing; keep pets, which swim erratically, out
of the water. Sharks are known to be attracted to such activity.
7. Do not enter the water if sharks are known to be present, and leave the water quickly and calmly if one is sighted. Do not provoke
or harass a shark, even a small one.
8. If fish or turtles start to behave erratically, leave the water. Be alert
to the presence of dolphins, as they are prey for some large sharks.
9. Remove speared fish from the water or tow them a safe distance behind you.
Do not swim near people fishing or spearfishing. Stay away from dead animals
in the water.
10. Swim or surf at beaches patrolled by lifeguards, and follow their advice.