Endangered Sharks: Predator or Prey

posted: 04/11/12
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Are sharks dangerous or endangered? The answer is both. On the danger side, most sharks are apex predators. This means they exist at the top of the oceanic food chain and possess few, or no, natural enemies. With their hunting stealth and multiple sharp teeth, they cruise the oceans in search of prey, such as seals, fish, large invertebrates and even, for some species, enormous whales. Their terminator tactics benefit water ecosystems by keeping other predators in check and oceans clean. Sharks worldwide are in peril now, however, so the endangerment side of the equation far outweighs any danger these creatures pose to humans.

The Most Endangered Sharks

The present situation is grave, since sharks are either at current risk of extinction or face uncertain futures. The World Conservation Union's IUCN Red List of Threatened Species includes at least 82 sharks and rays. Recently, the IUCN Shark Specialist Group (SSG) determined that 16 of the 21 oceanic shark and ray species caught in high-seas fisheries are at heightened risk of extinction, primarily due to targeted fishing for their fins — used in soup and folkloric remedies — and meat, as well as indirect take, known as by-catch, in other fisheries. Long-line fisheries, for example, can serve as death traps for sharks, which may get caught up in baited hooked lines stretching for up to 50 miles in the open sea. The distance is equivalent to the length of the state of Rhode Island. It's no wonder other researchers believe nearly 75 percent of the world's oceans are fished to their limits, meaning the target species are not recovering from the onslaught.

Based on both IUCN and data, sharks at greatest threat of extinction now run the gamut from very well-known species, like great white sharks, whale sharks and basking sharks, to sharks that might disappear before scientists can learn about them. This latter group includes the still-mysterious Ganges, Borneo, angular angel, pondicherry, speartooth and gulper sharks. Whitefin, smoothback angel, spinner, dusky, grey nurse, tope and porbeagle sharks are also at very low numbers.

Perhaps even more ominous is the fact that researchers have not been able to estimate the population counts for certain species. The fish wind up in conservation limbo, since "insufficient data" is available. Such sharks include the thresher, Java, kitefin, salmon, broadnose sevengill, bigeye sand tiger, narrowmouth catshark, great hammerhead, Argentine angel shark and megamouth, which was only first discovered in 1976. Some sharks could actually go extinct before scientists discover them, so mankind may never even know that they ever existed.

Why Sharks Are Vulnerable

For most of their 400 million years on the planet, sharks evolved in relative isolation from humans. More recently, our activities have encroached on their territory. Aside from the direct problems posed by finning and fishing, shark populations have been weakened by habitat destruction and environmental pollution. Toxic chemicals, such as those from discarded consumer electronics, can enter the food chain, accumulate in shark bodies, and may lead to shark immune system disorders and other health problems.

Shark populations cannot just bounce back from exploitation, due to their slow growth rates and long gestation periods. The shortest known gestation period in a shark is five months, such as for the bonnethead shark, and that is still a relatively long time compared to what other animals experience. The spiny dogfish has an even longer gestation time, at 22 months. Sharks are also slow growing. Mothers produce few pups per litter. In contrast, bony fishes tend to recover faster from over-fishing, since they can lay multiple eggs and reproduce at a much speedier pace.

How to Save Sharks

The recent SSG report calls on governments worldwide to address the global shark crisis by doing the following:

— Establishing and enforcing science-based catch limits for sharks and rays

— Ensuring an end to shark finning

— Improving the monitoring of fisheries taking sharks and rays

— Investing in shark and ray research and population assessment

— Minimizing incidental catch of sharks and rays

— Cooperating with other countries to conserve shared populations

Environmental organizations, such as the Sharklife Conservation Group, also urge individuals to do their part to help in the shark recovery effort. Individuals can write to state representatives about the problem, bring community awareness by writing to local papers and speaking to friends and colleagues, and avoid certain products, such as shark fin soup and goods made out of such things as sharkskin and shark teeth. Through volunteer time and donations, support to environmental groups perhaps makes the greatest positive impact, as evidenced by pressure that such organizations put on the United Nations in the early 1990s. In 1991, the U.N. banned high-seas drift-net fisheries, which led to a slow, yet discernible, recovery of salmon sharks in the North Pacific. Hope persists, so long as dedicated governments, groups and individuals do not give up on sharks.

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