Minggu, 05 April 2009

February 24, 2009--Fishers and scientists announced this week the catch, and release, of what is likely the world's largest known freshwater giant stingray.
The giant stingray, weighing an estimated 550 to 990 pounds (250 to 450 kilograms) was reeled in on January 28, 2009, as part of a National Geographic expedition in
The stingray's body measured 6.6 feet (2 meters) wide by 6.9 feet (2.1) meters long. The tail was missing. If it had been there, the ray's total length would have been between 14.8 and 16.4 feet (4.5 and 5 meters), estimated University of Nevada Biologist
Zeb Hogan.
Hogan was in Thailand searching for giant fish as part of the
Megafishes Project—an effort to document Earth's 20 or so freshwater giants.
The new find gives Hogan hope that the giant stingray, once overfished, may be more abundant than previously thought. And it may confirm the giant stingray as the heavyweight champ of the Megafishes Project.
"Honestly, we just don't know how much it weighed. But it's clear that the giant stingray has the potential to be the largest freshwater fish in the world," said Hogan, also a National Geographic
Emerging Explorer. (National Geographic News is owned by the National Geographic Society.)
"The Thai populations were once considered critically endangered, although with the discovery of new populations the stingray's abundance appears higher than previously believed," added Hogan. The International Union for Conservation of Nature (IUCN) currently lists the freshwater giant stingray as vulnerable.
Last March Hogan found a 14-foot-long (4.3-meter-long) ray near the Thai city of Chachoengsao. (
See previous giant stingray news and video.)
Freshwater giant stingrays are among the largest of the approximately 200 species of rays. They can be found in a handful of rivers in Southeast Asia and northern Australia.
Much is still unknown about the mammoth ray species, including whether or not it can swim out to and survive at sea. The species was first described scientifically only in 1989.
Hogan and his colleagues are still looking for new varieties and populations of the giant stingray.
--Tasha Eichenseher
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Photograph courtesy Zeb Hogan

Selasa, 31 Maret 2009

Ikan raksasa sungai Mekhong - Laos

Children pose with a Mekong giant catfish caught at Khone Falls in Laos, near the border with Cambodia, in August 2007.

A dam planned on the Mekong River in Laos will threaten the migration of the critically endangered fish, according to Zeb Hogan, who heads the National Geographic Society's Megafishes Project.

Photograph by Suthep Kritsanavarin

Noodling for Giant Catfish

Handfisher, or "nooder," Ann Tittle holds a giant flathead catfish. Also known as shovelheads or mudcats, the fish species is distinguished by its yellow-olive to dark brown body color, square tail, and a head that appears flattened between the eyes. According to the Ohio Department of Natural Resources Web site, "Flathead catfish spawn when water temperatures reach 700F and build nests in dark secluded shelters, such as natural cavities, undercut banks, or near large submerged objects. The eggs are laid in a compact golden-yellow mass, which is fanned continuously. The egg mass may contain as many as 100,000 eggs. After hatching, the young remain near the nest for several days in a large compact school. Flathead catfish feed almost exclusively on live fish."

Biggest Freshwater Fish in Cambodia

November 19, 2007Captured just before midnight on November 13 by fishers in Cambodia, this Mekong giant catfish is 8 feet long (2.4 meters long) ands weighs 450 pounds (204 kilograms). "This is the only giant catfish that has been caught this year so far, making it the worst year on record for catch of giant fish species," said Zeb Hogan (far right), a fisheries biologist at the University of Reno in Nevada. After collecting data on the fish, Hogan released it unharmed. Giant catfish were once plentiful throughout Southeast Asia's Mekong River watershed, including the Tonle Sap Riverhome of the fish in these exclusive pictures taken near Phnom Penh. But in the last century the Mekong giant catfish population has declined by 95 to 99 percent, scientists say. Only a few hundred adult giant catfish may remain. Since 2000 five to ten fish have been caught by accident each year throughout the Mekong area. Earlier this year Hogan, a National Geographic "emerging explorer," launched the three-year Megafishes Project to document the world's giant freshwater fish (See photos of other giant fish.) The project is funded in part by the National Geographic Conservation Trust and Expeditions Council. (National Geographic News is owned by the National Geographic Society.) Stefan Lovgren  More Photos in the News  Today's Top 15 Most Popular Stories  Free Email Newsletter: "Focus on Photography"

Listed as critically endangered by the World Conservation Union, the Mekong giant catfish is big but toothless, as shown in this exclusive photo of an animal captured November 13, 2007, in the Tonle Sap River near Phnom Penh in Cambodia.

"This fish was very weak after capture and so we stayed with it in the hopes that it would recover," U.S. biologist Zeb Hogan said.

The fish was released unharmed by Hogan, the staff of the Cambodian Department of Fisheries, and local fishers.

Residents of the Mekong River Basin, which includes the Tonle Sap, depend heavily on fish as sources of protein, but the region's fisheries have come under increasing pressure from rapid industrialization and a growing human population.