09 December 2005

Sharks may be extinct in a decade

Shark nets may reduce the incidence of attacks on swimmers but they are drastically diminishing general marine populations.

While the authorities are hard at work making the beaches as safe as possible, the use of shark nets has marine biologists, wildlife conservationists and scientists incensed as certain species head for possible extinction.

Andy Cobb, a member of the Shark Project based in KwaZulu-Natal which researches marine life, and who also runs a "shark school" to educate the public about these predators, said the numbers of sharks had decreased so drastically that scientists predict they will be extinct in 10 years.

"Since the installation of shark nets on our beaches in the '60s, the Natal Sawfish species has already become extinct. The nets are also killing turtles, stingrays and dolphins.

"The Indian Ocean bottlenose dolphin population along the KwaZulu-Natal coastline is being killed off faster than they can reproduce. They're down to only 450 animals. And the rare humpback dolphin numbers are also rapidly deteriorating because the nets along the coast, going to Richards Bay, are killing them off," he said.

Dr Sheldon Dudley, a scientist at the Natal Sharks Board, confirmed that shark nets do not only catch sharks but also a number of rays, turtles and dolphins each year. However he said all live animals were released and this amounted to about 67% of the annual catch of rays and 40% of the annual catch of turtles.

"In addition, as the populations of humpback and southern right whales increase from year to year, so the number of encounters between these species and the shark nets has increased, hence there is the potential for shark nets to have broader ecosystem effects. Such ecosystem effects are less easy to monitor," said Dudley.

But he also said a published analysis of shark attack statistics for the KwaZulu-Natal coast showed that the introduction of nets had reduced by more than 90% the rate of serious attacks occurring at protected beaches.

"The nets achieve their effect primarily by fishing for those potentially dangerous sharks that come into the immediate vicinity of the protected beaches," he said.

Cobb said: "Yes, I agree that the nets did their job - they fished out sharks. But sharks don't intentionally harm people unless they are enticed to do so.

"They are the ocean regulators who eat each other and the predators next on the food chain. Without them the predators will proliferate and the ocean will be a mess. They keep the ocean balanced.

"Already, since industrial times, the shark population has dropped by 90 percent. This horrendous loss of life is unacceptable. Renowned scientist Dr Leonard Compagno in 1986 declared that shark nets were no longer required because of the diminishing number of sharks. They should have been removed.

"Unfortunately municipal officers are more concerned with tourists than marine conservation," Cobb said.

Rudy van de Elst, director at the Ocean Research Institute at Durban's Ushaka Marine World, said: "Sharks are notoriously vulnerable. They are slow-growing, mature at a late stage and produce very limited numbers of young after a long gestation period. It's not surprising then that many shark populations have been drastically depleted.

"This applies as well to close relatives such as sandsharks and stingrays. Worst off is the sawfish, which must rank as one of the most endangered marine fishes and is effectively extinct in South African waters."

He said that sharks do not eat people and the odd encounter is invariably incidental and seldom a real feeding attack.

"In fact, less than five species hold any potential threat to humans and the others are either too small or simply have no interest in us.

"The issue of shark nets is increasingly controversial. The shark netting operation in KwaZulu-Natal has a long history. It was created at a time when there were several highly publicised attacks and also when the ecological value of sharks was poorly understood.

"Analysis of shark attack records reveals that a high proportion of these attacks took place under conditions that were considered unwise for safe swimming in the first place.

"These included swimming in dirty water, at night, alone, near river mouths and with bleeding fish on a spear. If one is to avoid these higher risk situations, the incidence of encounters would drop even further - and effectively to insignificant levels," he said.

Dudley said the Natal Sharks Board had implemented measures that were specifically aimed at reducing mortalities of marine animals.

"This year we installed a small number of drumlines, which are large drums with baited hooks suspended from them, in place of some of the netting at Richards Bay, and hope to extend the roll-out of drumlines as a partial replacement of nets at other beaches in 2006.

"A drumline is an alternative shark fishing device that not only is more selective than a net in terms of the shark species caught but also is considerably less likely to catch non-shark species. Finally, the Sharks Board will continue to work towards the development of an electrical repellent, which would be ecologically more friendly than shark capture devices."

Cobb said he doesn't believe drumlines will help. "It would still mean that shark numbers will be diminishing as this device is used specifically to fish out sharks," he said.

Source: www.int.iol.co.za


Post a Comment

<< Home