Posted on 01/23/2003 2:05:48 PM PST by cogitator
Shark Populations Plunge in North Atlantic
By Cat Lazaroff
WASHINGTON, DC, January 21, 2003 (ENS) - Shark populations in the north Atlantic have plummeted by more than half since 1986, shows a new study by researchers in Canada. The decline, blamed largely on overfishing, has affected top predators including the great white and hammerhead sharks, impacting marine food chains in ways that are still being studied, the researchers said.
The scientists, from Dalhousie University in Nova Scotia, Canada, looked at records of shark catches between 1986, when fishers and fisheries managers began keeping thorough records, and 2000.
CAPTION Hammerhead sharks like this one photographed in 1982 are thought to be nearing extinction. (Photo courtesy NOAA)
The team, led by doctoral candidate Julia Baum, learned that during that time, all coastal shark species saw population declines of 61 percent, on average. Blue shark numbers fell by 60 percent, tiger sharks by 65 percent, and thresher sharks by 80 percent.
Two of the largest species experienced some of the most devastating declines. Populations of great white sharks fell by 79 percent, while hammerhead numbers dropped by 89 percent.
"We estimate that all recorded shark species, with the exception of makos, have declined by more than 50 percent in the past eight to 15 years," the authors wrote in an article published in the January 17 issue of the journal "Science." Because of the slow maturation and low birth rate of most sharks, "recovery is expected to be slow," they add.
The researchers analyzed catch records from U.S. based longline fishing vessels seeking tuna and swordfish. While these vessels do not usually intend to catch sharks, which have limited value to them, they are required to report both their intended catch and their accidental catch, known as bycatch, to the National Marine Fisheries Service (NMFS).
These records form the largest set of data on sharks in the Northwest Atlantic. The researchers used them to extrapolate how the populations of shark species had fared over a 15 year stretch.
CAPTION Julia Baum, now a doctoral candidate in biology at Dalhousie University, led the research that uncovered the sharks' decline. (Photo courtesy Dalhousie University)
"Our results show that overfishing is threatening large coastal and oceanic sharks in the north-west Atlantic," the authors said. "The large and rapid declines we document are in addition to substantial historical reductions."
Ten years ago, longline fishers, who set mile long fishing lines with hundreds of baited hooks, changed their gear to allow sharks to free themselves from the lines. But the gear is not infallible, and the researchers say they factored in the altered fishing gear into their analyses.
The researchers said the problem is believed to extend around the globe, wherever longline fishing takes place and is not limited enough to prevent overfishing. Ransom Myers, a biologist at the University of Dalhousie and a coauthor of the report, has been developing models of how fishing could lead to the extinction of a variety of species, including salmon, turtles and sharks.
"Overexploitation of elasmobranchs (sharks, skates and rays) is known to have already nearly eliminated two skate species from much of their ranges," noted the team. "The magnitude of the declines estimated here suggests that several sharks may also now be at risk of large scale extirpation."
CAPTION A large white shark cruising offshore from the Farallon Islands in the Pacific Ocean. (Photo by Scot Anderson, courtesy NMFS)
While the researchers said not enough research has been done to show clearly what effect the loss of these top predators may have on the rest of the food chain, "pervasive overfishing of these species may initiate major ecological changes," they said.
Marine reserves in which fishing is banned will not solve the sharks' problems, the researchers noted, because sharks are wide ranging species that would not stay within the borders of protected areas. In some cases, reserves may actually worsen the problem for migratory species such as sharks, they added, because fishers are forced to congregate in other areas, where they may take a heavy toll on local fish populations.
For example, reserves close to shore might offer some protection to coastal shark species, while increasing pressure on open ocean species of shark.
CAPTION Overfishing has already led to the disappearance of the barndoor skate, the largest skate, from most of its historic range. (Photo by Don Flescher, courtesy NMFS)
"Clearly, if marine reserves are to be effective, their placement is of critical importance, and conservation initiatives must explicitly consider impacts on the whole community of species," the researchers said. "Emphasis on single species conservation, without controlling effort, simply shifts pressure from one threatened species to another and may actually jeopardize biodiversity."
The best solution, the Dalhousie team said, may be to extend ocean-wide protection to sharks such as is now in place for some tuna species and for sea turtles.
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Turtle pact signed here (Thailand)
Marine turtles across Southeast Asia and the Indian Ocean stand to benefit from a new international agreement conceived to ensure their long-term survival.
Twenty countries from around the region, including the Philippines, Sri Lanka, Tanzania and Vietnam, whose sea turtles face similar threats, committed themselves yesterday to work together to reduce those threats, conserve the turtles' natural habitats, increase public awareness and promote regional cooperation to save sea turtles.
The multilateral agreement was reached in Bangkok yesterday after the start of a three-day meeting of the signatory states to the Memorandum of Understanding on the Conservation and Management of Marine Turtles and their Habitats of the Indian Ocean and Southeast Asia.
UN Environment Programme executive director Klaus Toepfer described the meeting as historic. "The implementation of this agreement should mark a turning point in the conservation of Indian Ocean and Southeast Asian marine turtles."
"Our results indicate that they should be given conservation attention equal to that given other threatened large marine predators," they concluded. "We suggest that carefully designed marine reserves in concert with reductions in fishing effort could hold promise for safeguarding sharks and other large pelagic predators from further declines and ecological extinction."
Because of their speed and temperment you wouldn't have any chance against a mako. What helps is they rarely come into shalow water, and their eye sight is so good that targeting people is a rarity. A lot differnt when you have them on the line. They do attack boats and jump into cockpits.
The most dangerous for swimmers and bathers are the bulls tigers and whites. They come into shallow water and are aggresive.
Mako, thresher, porbeagle, and blacktips are big shark meat sellers.
When we tag sharks the instructions are to cut off close to the hook but don't remove the hook because a jaw hooked shark survives, no problem. Trying to remove the hook may do more damage. Tagged sharks released with hooks in the jaw are recovered years later with no adverse effects. A gut hooked shark is another matter and they more than likely have trouble after release. - Tom
How big?
(That gull looks like it's making an abrupt STOP! ;-)
This past summer Thresher pups were being caught in Ambrose Channel right at the mouth of Raritan Bay by fluke fishermen. Unfortunately I didn't get any of them or any of the 50 lb rays that came throught either. :(
The hook will eventually rust out; but in my opinion not in a few days or weeks as is commonly stated.
One time we had a shark to the boat with 3 other hooks in his mouth;probably from tuna fishermen or longliners. We made an exception to just cutting him loose, and kept him alongside and removed all four hooks, and he swam off no problem. - Tom
No, Bush's Baked Beans do not have anything to do with this particular trend.
It depends on the species. The worst is the mako that has excellent eyesight and can snap at you unexpectedly as your hand comes down the wire.
The problem isn't just the bite it is infection.
A friend cut a shark loose went to the other side of the boat to cut another loose. The first angler put the rod in the holder and left the cut wire hanging into the water. The second shark went around the boat to where the first shark was cut loose. When my friend reached down to cut it loose, it wrapped the wire that was hanging in the water, and unexpectedly pulled his hand down with the wire. He got 27 stitches from the upper teeth of the shark. When I talked to him he had his arm in a sling and had been shot with just about every antibiotic the hospital.
If you get your cutting hand caught between the shark and the wire when t rolls, and the shark turns to bite your arm or shoulder, you have to take your free hand and put it between the sharks upper jaw and snout to hold it off until you get your other hand free.
Usualy it is not a problem except the more you do it the closer to the hook you get. I have cut loose over 700 big blue sharks in one season. Now because of so many cod trips I cut loose 100-300 sharks a season.
But like a baseball player, if you play the game long enough, you will get hit with a pitched ball. I always have that in the back of my mind. - Tom
Normally we just cut the wire close to the hook. - Tom
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