There is much concern about shark fishing and shark fining. Ocean conservation is at stake as predators in all the world oceans are subjected to over-fishing. Caribbean and Andaman Sea fisheries (Malaysia) are especially stressed. Growing support for eco-tourism based experiences like swimming with sharks and swimming with dolphins promise to outstrip the economic benefit of over-exploitation. The following report looks at the experience of one of our scuba divers in assessing a shark conservation project off South Africa.
During
a recent photo expedition Jeff had a surprise visit from a big Tiger Shark.
Jeff and Gerry tell the story:
“All
of a sudden something was holding on to my scuba gear and shaking me like a
feather. I was so busy getting some great shots that I didn’t see this big one
come up behind me.”
“I
was pretty lucky that I wasn’t hurt, but it seemed like the Tiger was just
trying to figure out what I was.”
The Tiger
Shark, which generally hunts at night, has a reputation for eating anything and
everything and for an aggressive nature. Most of the time, Tiger Sharks eat
fish, squid, seabirds, sea mammals, other sharks, and turtles.
Out
of more than 360 shark species, only four have been involved in a significant
number of fatal attacks on humans over the last 60-70 years: the great white,
tiger, oceanic white tip, and the bull shark. Culling Tiger Sharks a few days
after an attack probably has little value since most are nomadic and the
offending animal may well move on. Some governments ‘protect’ swimming beaches
with shark nets that catch any sharks swimming along the
coast.
Even
small Tiger Sharks require a lot of watching and big ones can weigh up to 1000
kg and reach 6-7.5 metres. They get the name Tiger from the vertical stripes
and not from their diet. Based on diet, they are more like ‘trash-can sharks’
since stomachs have been found to contain buckets, rolls of wire, gas cans,
paint brushes, and baseballs. One even contained old tires.
So
why did the shark bite Jeff’s metal air tank?
First,
the shark was confused by the metal on Jeff’s back. Tiger sharks have small
pits (ampullae of lorenzini) on their snout and along their upper bodies which
can sense weak electrical fields. Normally these sensors detect fish when the
water is too murky for their usually sharp eyes to see. But different kinds of
metals generate weak electric currents in seawater and alert the shark that
something is going on.
Secondly,
the Tiger Shark’s keen sense of smell would not be sure if the smell of human
meant the next meal or danger. You don’t grow up to be a big shark without a
little caution!
Finally,
sharks adopt the same strategy as children; if you are unsure what something
is, just put it in your mouth and taste it.
“Diving
with Tiger Sharks is awesome and something I will never forget. The footage
will be great for documentary work and we always learn something about these
incredible animals. We have to work fast as Tiger Sharks are disappearing
because of the shark fin trade and sport fishing.”
Nature
has equipped these sharks with all the gear to be great hunters: they can sense
movement in the dark, feel water pressure waves from injured animals, smell
traces of blood in the water, and have excellent vision. They are fearless and
haven’t learned to stay away from boats and fishing gear.
