Friday, August 7, 2009

Endangered Sharks

Sandbar shark

A third of the world's open water sharks, including the great white and hammerhead, face extinction, according to a major conservation survey. Those species that are hunted on the high seas are particularly at risk. In that group, more than half are in danger of dying out, reports the Shark Specialist Group at the International Union for the Conservation of Nature (IUCN).

New Jersey waters have long been the home for a number of shark species. Though no species is on the NJ endangered list, their protection is still a concern as species are federally and globally endangered. The inevitable summer news story about a sighting or attack at the Jersey Shore always brings to mind images from films like Jaws and stories like that of the 1916 NJ attacks.

The Jersey Shore shark attacks of 1916 were a series of shark attacks between July 1 and July 12 in which four people were killed. Scientists are still not sure which shark species was responsible and the number of animals involved, with the great white shark and the bull shark most frequently being blamed.

Though there is an assortment of sharks that can be found in New Jersey waters, most would be found offshore in oceanic waters and are rarely a danger to swimmers, surfers or divers. Though they can often be put off by the noise and bubbles, they should still always be treated with caution.

Blue, basking, great white, shortfin mako, porbeagle, thresher, and other "inshore" and "dogfishes " are all found in our waters. The "dogfish" is actually a generic name for a large number of small, generally harmless and unaggressive sharks, not all of which are very closely related.

Most NJ shore visitors are familiar with skates which are closely related to sharks and rays. Skates can be found in shallow bays to deep-sea habitats and live on the bottom of the sea floor. If you have ever been fishing offshore, you probably have pulled one of these doormats up thinking you had a huge fish on the line.

Their flat body and large fins give skates the appearance of flying when swimming through the water. They eat a variety of crustaceans, mussels, clams, snails, and
worms. The best-known NJ species is the little skate, which is 1 to 2 feet (30 to 61 centimeters) long. A larger skate that lives along the New Jersey coast is the barn-door skate.

Skate are oviparous (egg layers) and after a breeding season, female skates can store sperm to fertilize and secrete eggs continually throughout a 3-4 month period. The eggs are encased in a tough, leathery protective egg case that is black, with four points and are frequently found washed up on the beach by bathers.

Collapsing shark populations are mainly caused by overfishing. Some 100 million sharks are caught in commercial and sports fishing every year. Sharks are especially vulnerable to overfishing because most species take many years to mature and have relatively few young. Sharks are prized for their meat, and in Asia especially for their fins, a prestige food thought to convey health benefits. For decades, significant numbers of sharks, including blue and mako, have perished as "by-catch" in commercial tuna and swordfish operations.

The smooth hammerhead, great white, basking, and oceanic whitetip sharks are listed as globally vulnerable to extinction, along with two species of makos and three types of threshers.

The Sand Tiger shark is fairly common off Atlantic City and Cape May.

For example, the Spanish fleet of so-called surface longline fishing boats ostensibly targets swordfish, but 70 percent of its catch, by weight, from 2000 to 2004 were pelagic sharks. There are currently no restrictions on the number of sharks that these fisheries can harvest.

Europe is the fastest growing market for meat from the porbeagle and another species, the spiny dogfish.

What would be the impact from the loss of sharks from the world's oceans?

"Removing large predators would deprive ecosystems of players that have been around for more than 400 million years," said Francesco Ferretti, a researcher at Dalhousie University in Halifax, Canada.

Recent studies have shown that sharp reductions of coastal shark populations along the US East Coast and in the Gulf of Mexico caused major disruptions throughout the food chain, including on aquaculture.

The IUCN issues the Red List of Threatened Species, the most comprehensive and authoritative conservation inventory of the world's plants and animals species.

Shark Research Institute

Scuba Diving NJ - info on sharks
Images: nmfs.noaa.gov

No comments:

Post a Comment