But something else would be changed as well -the whole ecology
of the ocean. Predators control the populations of their prey
species in a beneficial way. They eliminate diseased and
genetically defective individuals, and they stabilize population
fluctuations. On land, when we have removed the natural predators
of deer; for example, their populations have exploded until they
overgrazed their food supply and died of starvation and disease. In
the ocean we are not sure what all the consequences of removing the
apex predators from the food pyramid might be. We do have one
example, though. A shark fishery in Tasmania collapsed after two
years of over fishing. Shortly afterwards, the fishery for spiny
lobsters also collapsed and fishermen observed a lot of octopus in
the area. Octopuses are both major predators of spiny lobster and
an important food item for sharks. It seems that once the numbers
of octopus were no longer controlled by the sharks, they became too
numerous and decimated the lobsters. Economically, for those other
than shark fishermen, it doesn't make sense to allow sharks to be
fished out, not only because of the possible damage to sustainable
fisheries, but also because of the loss of earnings from divers
coming to see sharks. Worldwide, shark-watching has become a
multi-million dollar business.
Why do shark populations collapse so quickly when people begin
fishing them? The answer lies in the life history of these animals.
In many aspects, sharks are more similar to mammals such as whales,
dolphins, or ourselves, than to other fish. Whereas most fish reach
maturity in only a few years and produce thousands or millions of
eggs per year; sharks take many years to reach maturity. Some
species may not begin to reproduce until they are over 15 years
old. Some species produce as few as two pups biannually, averaging
only one offspring per year: So when a population is over fished,
it may take many years to recover; or it may never recover: Some
scientists believe that sharks should never be fished at all, that
their biology is too fragile to withstand any exploitation. Perhaps
sharks should have the total protection given to marine mammals in
many countries. Unfortunately, sharks do not have big 'fan clubs'
as dolphins do.
Although both are large predators with slow reproductive rates,
sharks are handicapped, from a.: public relations perspective, by
the fact that their mouths appear to be frowning, and that they
must open their mouths to pass water over their gills, exposing
their teeth. Dolphins, on the other hand, always appear to be
smiling, because of the shape of their mouths. Since they breathe
through the blowholes on top of their heads, they do not have to
open their mouths and expose their formidable teeth in order to get
oxygen. But even the dolphin's smile may not protect it from the
greed inspired by the high prices being offered by international
buyers of shark fins. In a number of countries, fishermen are
slaughtering dolphins to chop up for shark bait.
