Post by tekmac on Jul 13, 2005 9:01:39 GMT -5
Imagine a world without Jaws. Within less than a century, there will be no more large sharks in the world's oceans; they'll all be gone – the great whites, makos, threshers, the huge whale sharks, the gentle basking sharks that eat plankton – all gone.
"In my opinion, mako sharks will disappear in the next 25 to 30 years, if trends continue as they are," says Jeff Graham, a shark expert, research physiologist and marine biologist at the Scripps Institution of Oceanography.
While not optimistic, he believes these populations may yet have a chance for survival, depending in part on gaining more knowledge about the mysterious lives of sharks. The waters off San Diego's coastline serve as the most active nursery on this side of the Pacific Ocean for mako and thresher sharks. The mako moms give birth to their young here, but scientists have yet to discover where makos do their romancing. That breeding area may be in Mexican waters, "but we have no Mexican data," says Graham.
We do know that makos grow to over 12 feet and 1,000 pounds; they slice through the water like a jet fighter at speeds that can have bursts of over 60 miles per hour. Unlike most other sharks, they leap out of the water; jumps of 20 to 30 feet have been recorded. A few years ago, a 10-foot mako jumped out of the water and into the boat of a 69-year-old Fijian fisher. "Immediately, the shark proceeded to eat the fisherman," according to a newspaper report.
Do such stories, when overplayed, hasten their destruction? Maybe. Shark attacks are, in fact, rare. But the nightmare images serve a purpose. As with tigers, grizzly bears and our local mountain lions, sharks remind us that we're not the only, well, fish in the sea.
In any case, the possible disappearance of large sharks is part of a larger issue. Many of the oceans' fisheries are in extreme jeopardy, a conclusion reached recently by both a federal commission appointed by President Bush and the Pew Oceans Commission. Among the reasons: pollution, development and over-fishing.
Traditionally, scientists have thought that sport fishers take only about 2 percent of total fish landings. But in 2004, a team of marine biologists funded by the Pew Charitable Trusts declared that sport fishers were responsible for nearly one-fourth of the total catch for commercially valuable species. That figure is, of course, controversial. (Certainly catch-and-release sport fishing helps.) But commercial fishing remains the harshest influence.
Sharks are especially threatened by fishermen who target sharks for their fins, a primarily Asian delicacy. Some commercial fishermen catch the sharks, slice off their dorsal and pectoral fins, and throw them back into the water, where the fish sink and die. Though now illegal off U.S. coasts, shark fin harvesting continues to grow, in pace with the booming Asian economies.
Numerous sharks are also killed by commercial fishermen using gill nets to target swordfish. Every time a gill net is set, it accidentally kills approximately eight blue sharks – as well as threshers and makos, according to Graham. But regulation is tricky.
For example, the federal government has barred commercial fishing for swordfish north of Point Conception, mainly to protect leatherback turtles from the nets. One unintended consequence is that commercial netters from Northern California and Oregon now travel south, into our waters – the vulnerable nurseries of makos and threshers. Creating marine reserves is no panacea, either. Fish in these reserves, while protected from human predation become easy prey for quick-learning marine mammals, such as sea lions. Well-fed sea lions have more offspring. As a result, fish in and outside of the reserves are further threatened.
Facing such complex challenges, and the need for a multifaceted habitat policy, Graham and a handful of graduate students are rushing to tag as many makos and threshers as they can. In small boats off the San Diego coast, they chum the waters with chopped fish, and drop into the water dead mackerel with small transmitters lodged in their bodies. The tags, swallowed by the sharks, then tell the scientific team about the temperature and depth status of the fish. Graham hopes that more knowledge about shark behavior will help protect them, by fine-tuning commercial fishing. "For example, we might find that a net dropped 10 feet deeper may better protect sharks," he says.
If Graham were the emperor of the oceans, he would ban the use of fishmeal (made of ground fish) in fish farming, and substitute soy-based food for aquaculture. And he would declare a moratorium on all commercial fishing, to allow the fisheries to recover. That edict, he admits, will never fly, or swim. But unless more is done – and more is known – many species, including the large sharks that we love to hate, will, as Graham says, "simply go away."
Louv's column appears on Tuesdays. He can be reached via e-mail at rlouv@cts.com or via www.thefuturesedge.com.
"In my opinion, mako sharks will disappear in the next 25 to 30 years, if trends continue as they are," says Jeff Graham, a shark expert, research physiologist and marine biologist at the Scripps Institution of Oceanography.
While not optimistic, he believes these populations may yet have a chance for survival, depending in part on gaining more knowledge about the mysterious lives of sharks. The waters off San Diego's coastline serve as the most active nursery on this side of the Pacific Ocean for mako and thresher sharks. The mako moms give birth to their young here, but scientists have yet to discover where makos do their romancing. That breeding area may be in Mexican waters, "but we have no Mexican data," says Graham.
We do know that makos grow to over 12 feet and 1,000 pounds; they slice through the water like a jet fighter at speeds that can have bursts of over 60 miles per hour. Unlike most other sharks, they leap out of the water; jumps of 20 to 30 feet have been recorded. A few years ago, a 10-foot mako jumped out of the water and into the boat of a 69-year-old Fijian fisher. "Immediately, the shark proceeded to eat the fisherman," according to a newspaper report.
Do such stories, when overplayed, hasten their destruction? Maybe. Shark attacks are, in fact, rare. But the nightmare images serve a purpose. As with tigers, grizzly bears and our local mountain lions, sharks remind us that we're not the only, well, fish in the sea.
In any case, the possible disappearance of large sharks is part of a larger issue. Many of the oceans' fisheries are in extreme jeopardy, a conclusion reached recently by both a federal commission appointed by President Bush and the Pew Oceans Commission. Among the reasons: pollution, development and over-fishing.
Traditionally, scientists have thought that sport fishers take only about 2 percent of total fish landings. But in 2004, a team of marine biologists funded by the Pew Charitable Trusts declared that sport fishers were responsible for nearly one-fourth of the total catch for commercially valuable species. That figure is, of course, controversial. (Certainly catch-and-release sport fishing helps.) But commercial fishing remains the harshest influence.
Sharks are especially threatened by fishermen who target sharks for their fins, a primarily Asian delicacy. Some commercial fishermen catch the sharks, slice off their dorsal and pectoral fins, and throw them back into the water, where the fish sink and die. Though now illegal off U.S. coasts, shark fin harvesting continues to grow, in pace with the booming Asian economies.
Numerous sharks are also killed by commercial fishermen using gill nets to target swordfish. Every time a gill net is set, it accidentally kills approximately eight blue sharks – as well as threshers and makos, according to Graham. But regulation is tricky.
For example, the federal government has barred commercial fishing for swordfish north of Point Conception, mainly to protect leatherback turtles from the nets. One unintended consequence is that commercial netters from Northern California and Oregon now travel south, into our waters – the vulnerable nurseries of makos and threshers. Creating marine reserves is no panacea, either. Fish in these reserves, while protected from human predation become easy prey for quick-learning marine mammals, such as sea lions. Well-fed sea lions have more offspring. As a result, fish in and outside of the reserves are further threatened.
Facing such complex challenges, and the need for a multifaceted habitat policy, Graham and a handful of graduate students are rushing to tag as many makos and threshers as they can. In small boats off the San Diego coast, they chum the waters with chopped fish, and drop into the water dead mackerel with small transmitters lodged in their bodies. The tags, swallowed by the sharks, then tell the scientific team about the temperature and depth status of the fish. Graham hopes that more knowledge about shark behavior will help protect them, by fine-tuning commercial fishing. "For example, we might find that a net dropped 10 feet deeper may better protect sharks," he says.
If Graham were the emperor of the oceans, he would ban the use of fishmeal (made of ground fish) in fish farming, and substitute soy-based food for aquaculture. And he would declare a moratorium on all commercial fishing, to allow the fisheries to recover. That edict, he admits, will never fly, or swim. But unless more is done – and more is known – many species, including the large sharks that we love to hate, will, as Graham says, "simply go away."
Louv's column appears on Tuesdays. He can be reached via e-mail at rlouv@cts.com or via www.thefuturesedge.com.