RECENT reports claiming that about a third of the world's open water sharks face extinction is no surprise to bluewater anglers. Sharks have been slaughtered needlessly for years.
What the reports don't explain is why the slaughter is serious.
In many countries where stocks of bony fish have fallen away, recovery was made possible through sound fisheries management. In some instances, this has involved fish breeding. Most bony fish grow fast and many reach sexual maturity within 12 months. Some, like snapper, are serial spawners and can produce thousands of young.
Sharks have been around for 300 million years, or 100 times longer than humans, and are biologically different to bony fish. Overfishing is a potentially bigger disaster as sexual maturity in many sharks can take as long as humans, with gestation periods as long or longer.
Most sharks reproduce only once every two years and this can vary from dog-size litters for gummy sharks to just one or two young. A thresher shark gives birth to two to four pups after a nine-month gestation. However, with infant mortality rates exceeding 50 per cent it is difficult for sharks to maintain their numbers.
In an interview a few years ago, fisheries consultant Dr Julian Pepperell said great whites do not mature until they are nine to 11 years old. These sharks have five to 10 pups. Reproduction is thought to occur biennially, and perhaps only five times in a lifetime.
Despite this slow reproduction rate, their survival is better than that of tiger sharks.
Great whites can be 20 to 30 kg and about 1.2m to 1.65m long at birth; tiger sharks can have 100 babies but each weighs only about 1kg.
A great white is born big enough to eat many predators, including the tiger shark.
Dr Pepperell said that despite their vulnerability at birth, tiger sharks are prolific, faster growing than whites and not at risk.
Taronga Zoo in Sydney produced a fact sheet on sharks, showing that more people die from slipping in the bath or from bee stings than shark attacks.
Sharks will sink if they stop swimming because they don't have a swim bladder like other fish. One shark at the zoo swam 300,000km in six years (almost eight times around the world).
Adult whites will eat penguins, turtles, and other sharks. Tiger sharks might be the least selective scavengers - among things found in their stomachs have been cans, car numberplates, a cow's head, dogs, boots, beer bottles, a bag of potatoes and even sheep.
In the late 1960s, I caught gummy sharks on a regular basis. I reckoned every time I fished the flood tide on a moonlit night I was in with a reasonable chance of hooking one of these toothless sharks. Then the gummy sharks, once common in our bays and along our surf beaches, became a rare catch.
The ban on inshore shark netting and long-lining within three miles in 1993 is credited with the resurgence of gummy sharks.
Nowadays anglers in both Western Port and Port Phillip Bay, and those fishing offshore in Bass Strait are enjoying the benefits. This is also true along our surf beaches. School or snapper sharks are also returning, albeit more slowly. Gummy sharks have reached a level where they are again a regular capture and offer a prime example of the benefits of a sensibly managed fishery.
The worst US nightmares are reports that came out of a Florida fishing tournament in 1987, when two contestants reeled in finless tiger sharks that could only wriggle along the bottom and apparently had taken the cut bait because they couldn't catch anything that swam.
There was also a report of a tiger shark beaching itself. It had no fins but managed to wriggle ashore in caterpillar fashion after being dismembered, presumably by a longliner.
Shark fins are at a premium in Asia, the meat of no account. This is a tragic predicament for a creature that has only its own kind and man to fear.
- Steve Cooper can be heard on the Casting Off program on Radio Sport927 between 4.30-6.30am on Saturdays.
