Friday Fishy News - July 27

[Flattieman]

Man dies of wounds after trying to use dynamite to fish near Sidon harbor

By Mohammed Zaatari

The Daily Star (Lebanon)

July 24

A Lebanese fisherman was killed next to Sidon's harbor while using dynamite to fish during the weekend. Said Maoush, 60, was trying to throw a stick of dynamite into the water when the stick exploded. The fisherman's left arm was blown into the sea and his face was burned. Maoush died of his wounds soon after he was rushed to a nearby hospital.

Blast or dynamite fishing became very popular in Lebanon during the years of the 1975-1989 Civil War. Following the conflict, blast fishing was prohibited by the government.

The Coast Guard conducts extensive patrols to deter blast fishing, but a number of fishermen nevertheless still use the technique, because of its efficiency in killing large numbers of fish, despite the potentially deadly outcome of the practice.

Environmental activist Mohammad Sarji told The Daily Star that roughly 12 people per month fall victim to the practice.

Dynamite fishing is easy and cheap, as fishermen use dynamite or homemade bombs made from locally available materials. Fish are killed by the shock of the blast, and the fishermen later collect the dead fish from the water's surface. Blast fishing is illegal in many waterways around the world and is also prohibited by a number of religions, such as Islam.

"The explosions indiscriminately kill large numbers of fish and other marine organisms in the vicinity, and a number of fishermen are killed or severely wounded when using primitive bombs and dynamite sticks," Sarji said.

Sarji added that explosions were particularly harmful to fish eggs and the reproduction cycles of fish and marine organisms.

Sarji said the Internal Security Forces had recently arrested fishermen using dynamite along the southern coast from the town of Sarafand to the border town of Naqoura.

"Let us hope this step will eradicate the use of dynamite in fishing," he added.

One fisherman, who lost an arm some 30 years ago while fishing with sticks of dynamite, agreed to share his experience.

"I warn my children, who also work as fishermen, not to make use of dynamite fishing, as rewarding as it might seem," said the fisherman, who asked to be identified as Hilal.

China's Giant River Fish, the World's Largest, Feared Extinct

By Stefan Lovgren

National Geographic

July 26

If the world's largest freshwater fish still exists, Wei Qiwei will be there to save it.

"I believe it's out there," said Wei, as he scanned the murky Yangtze River from his sleek, 63-foot (19-meter) rescue vessel.

Wei is one of China's foremost experts on the Chinese paddlefish, a leviathan that reportedly can grow 23 feet (7 meters) long and weigh half a ton.

But the odds of finding even a single one of the aquatic giants may be steadily diminishing.

No adult Chinese paddlefish have been caught in the Yangtze River by fishers since 2003. Even more worrisome, no young paddlefish have been seen since 1995.

"When you don't see juveniles, we think maybe there's no spawning," said Wei, who heads a research laboratory at the Yangtze River Fisheries Research Institute in Jingzhou.

He and other experts fear that even if individual paddlefish are found in the Yangtze, the species itself, if unable to reproduce, could be on an irreversible path to extinction.

Spawning Ground

The Chinese paddlefish is also known as the elephant fish, because its long snout resembles an elephant's trunk.

The predators feed on other fish, as well as small amounts of crab and crayfish.

Prized for their rich, plentiful meat, the giant animals are said to have been commonly offered as gifts to the Chinese emperor during imperial times.

In the 1970s hundreds of paddlefish were caught each year by fishers on the Yangtze River.

Then, in the 1980s, the population dropped dramatically, Wei said.

The culprit for that loss can be found by taking a 20-minute boat ride up the river from the city of Yichang to the giant Gehzouba hydroelectric dam.

The dam, completed in 1983, divided the Yangtze River into two sections, cutting off the migratory route of the paddlefish.

"The paddlefish travel long distances, from their forage grounds in the middle and lower part of the Yangtze River—and sometimes the coastal waters—to their spawning grounds in the upper river," Wei said.

"The dam separated the feeding area from the spawning ground."

The spawning process for paddlefish is particularly sensitive because females do not become sexually mature until they are seven or eight years old, he added.

The newly built Three Gorges Dam, the largest hydroelectric dam in the world, which sits 30 miles (48 kilometers) upriver from the Gezhouba Dam, has further reduced paddlefish habitat, Wei said.

Two more dams are now being planned for the upper reaches of the Yangtze River.

Last Animal Caught

Fisheries biologist Zeb Hogan was also aboard Wei's boat on his recent ride up the Yangtze.

Hogan heads the National Geographic Society's Megafishes Project, a three-year program to assess the conservation status of the world's largest freshwater fishes.

The plight of the Chinese paddlefish underscores the urgent need to protect the river giants, said Hogan, who is a National Geographic Emerging Explorer.

"Here is what is perhaps the world's largest freshwater fish, and it's close to extinction," he said.

An 11-foot (3.3-meter) paddlefish was caught by fishers in December 2002, Wei pointed out. It died after 29 days in captivity.

The following month, a 12-foot (3.5-meter) paddlefish was caught in Yibin in the upper Yangtze.

Fisheries law enforcement officials immediately contacted Wei. During the eight hours it took him and his crew to travel to Yibin, Wei gave suggestions to officials on how to handle the fish, which survived.

Before it was released back into the river, Wei planted a location transmitter on the paddlefish.

Wei has since lost the signal, but he believes this fish is still alive.

"These fish can live for maybe 50 years," he said. "I'm sure it's still there."

Underwater Caves

Wei and Hogan have agreed to embark on a joint expedition next year to look for Chinese paddlefish.

Wei believes the upper Yangtze provides a possible last refuge for the fish and that there might be up to a dozen individuals left.

"That area has many deep pools and underwater caves where the fish can hide," he said.

Wei vowed not to retire until he finds a paddlefish.

"I have another 20 years to go," he said. "I'm not giving up that easily."

Gardening Fish "Domesticate" Crops of Algae

By Helen Scales

National Geographic

July 23

Damselfish can appear quite contrary to species that wander into their gardens of algae by aggressively chasing off larger fish and even nipping at human divers.

But for some damselfish species, protecting their "crop" is a matter of survival for both the fish and the algae, according to recent research.

The dusky farmerfish has developed a co-dependent relationship with a species of the red algae Polysiphonia.

Both creatures are found on coral reefs in the Ryukyu archipelago, a scattering of islands that stretches between southern Japan and Taiwan.

"Not only do the fish rely on the algae as a source of food, but the algae only survive well if they are farmed," said Hiroki Hata, a marine biologist from Kyoto University in Japan.

"We saw dusky farmerfish feeding exclusively inside their farms, which are dominated by a single type of algae that we called 'Polysiphonia species one,'" Hata said.

Scouring the reefs also revealed that Polysiphonia species one grows only inside the gardens of dusky farmerfish.

In total, Hata and colleagues identified four new Polysiphonia species that have adapted to rely on particular types of damselfish.

"Life inside the damselfish gardens is so good for the algae that they seem to have come to depend on being farmed," Hata said.

Guarding and Weeding

Damselfish are among the handful of animals—including humans, ants, and salt-marsh snails—that are known to cultivate beneficial crops.

Although they are relatively tiny—on average about 6 inches (15 centimeters) long—damselfish seem to tend their gardens with zeal.

Unwanted sea urchins and starfish are ejected from the farms, and unpalatable algae are meticulously weeded out to promote lush turfs of the preferred species.

In a study that appeared last October in the journal Biology Letters, Hata and colleagues described what happens when the damselfish are removed from their plots. The team built cages to set around the actual gardens and thus control what could get in.

If all herbivores are kept out—including the damselfish—within a week the Polysiphonia gardens become completely overrun by other species of algae.

"When only the damselfish are removed," Hata said, "it takes just a couple of days for other grazing fish to move in and obliterate all the algae growing inside the gardens."

Spreading the Seeds

Nancy Knowlton is a marine biologist at the Scripps Institution of Oceanography in La Jolla, California.

Knowlton, Hata, and colleagues plan to study similar farming damselfish on the reefs of Panama later this year.

One of the questions the team wants to examine, Knowlton said, is how the fish developed such a specialized relationship with the algae.

Many kinds of farming animals practice vertical inheritance, in which they transfer some of their crops from established gardens to set up new colonies.

But dusky farmerfish instead seem to establish new territories when waterborne spores or fragments of algae drift to new parts of the reef from nearby gardens. The fledgling plots can then flourish under the care of new damselfish.

"There is no evidence that tiny larval damselfish would be able to transfer algae from their parental gardens to their own new territories," Knowlton said.

"Without vertical inheritance it's unclear how the specific fish-algae relationships could come about."

Meanwhile, Hata said, existing damselfish gardens face an uncertain future as global warming continues to negatively impact coral reefs.

Although it is difficult to predict, he noted, increased sea temperatures could eventually lead to a breakdown of the relationship between fish and algae.

"The damselfish depend on new coral skeletons to establish their gardens on," he said.

"Without new coral growth, older skeletons will erode away and eventually could leave the damselfish with nowhere to cultivate algae."

Male Stickleback Fish Masquerading In Murky Waters

ScienceDaily

July 22

Where humans lower water quality, poor quality stickleback male fish trick unsuspecting females.

Finding a decent, honest mate is challenging enough without the added problem of reduced visibility caused by human-induced changes to the aquatic environment. Yet this is precisely the sort of dilemma female stickleback fish are facing in the Baltic Sea, according to a recent study published in the August issue of the American Naturalist by Dr. Bob Wong, an Australian researcher from Monash University, and his Scandinavian colleagues, Dr. Ulrika Candolin from the University of Uppsala and Dr. Kai Linstrom from the Åbo Akademi in Finland.

An increase in nutrient input in the Baltic is compromising water clarity by promoting algal blooms. Dr. Wong and his colleagues were interested in finding out whether this, in turn, might lead to a break down in the honesty of sexual displays used by male sticklebacks to attract females. They did so by examining the courtship effort of good and poor condition males in the absence and presence of a rival male in both clear sea water and water rendered turbid by algae.

"Under reduced visibility caused by the presence of algae, poor quality males are able to lie about their physical condition to unsuspecting females by displaying at a higher rate without the risk of attracting the wrath of rival males," says Dr. Wong. "Since poor condition males are also more likely to eat the eggs that they're suppose to be tending, this is bad news for females who rely on the honesty of male sexual displays to select mates with superior parental qualities."

Catch-Release Angling Injures Fish

By Jennifer Viegas

Discovery News

July 20

Catch and release fishing seems like a win win-situation, with recreational anglers experiencing the thrill of a catch, while their prey can, in theory, swim safely away.

But that's not always the case, according to a new study that found fish, including sharks, may suffer so much trauma during the event that they could die shortly thereafter. The findings, which will be published in next month's Journal of Experimental Marine Biology and Ecology, primarily apply to hook and line anglers, since the catches of seine net users rarely died upon release.

"Small sharks are susceptible to predation by larger sharks following release," lead author Sascha Danylchuk told Discovery News.

Danylchuk, a researcher at the Cape Eleuthera Institute in the Bahamas, added that even if catches survive, they might be less able to reproduce or more susceptible to disease.

Although the findings apply to sharks and other fish, Danylchuk and her team focused on bonefish, a tropical fish whose wariness and speed make it a sought-after target among recreational anglers.

The scientists angled and landed 88 bonefish in Eleuthra, the Bahamas, with fly-fishing equipment. A second group of fish was caught using a seine net. Following releases, each fish was observed for up to one hour.

Fish that experienced a loss of equilibrium, or an inability to swim away normally, were six times more likely to die than others.

"When a loss of equilibrium has occurred, what we as anglers see is a fish rolls on its side or ends up nose diving to the bottom rather than swimming away with some vigor," Danylchuk said.

She compared it to a person being asked to walk a straight line after having been spun around in a circle, or to a runner giving his all, "essentially what a fish is doing when it is being angled," and then not being able to walk very well afterwards because muscles are full of lactic acid.

Like marathon runners, it is as though the caught fish "hits a wall."

"Extensive exercise, in combination with air exposure, a hook wound and extensive handling all can play a role in loss of equilibrium," she said.

During the study, predators, including lemon sharks and great barracuda, quickly nabbed the bonefish that experienced the equilibrium problem. The scientists think traumatized fish may even release stress chemicals, which function like a dinner bell to watchful predators.

In an unrelated study, scientists at the New South Wales Department of Primary Industries are investigating ways to boost the survival rates of fish that are caught and then released by anglers. Preliminary findings suggest that a quick and easy technique can help to eliminate unnecessary deaths.

"Simply cutting the line, rather than attempting to remove hooks swallowed by mulloway and yellowfin bream, increased their survival from 12 percent to more than 85 percent," said Matt Broadhurst, one of the researchers.

Broadhurst and Danylchuk also recommend that catch and release fishermen should minimize air exposure, use landing nets without knotted mesh, use barbless hooks to help expedite hook removal, and avoid sunscreen and bug repellent on hands, since Danylchuk said, "these can affect the slime coating on fish."

Trophy fish photos are still possible, she said, but fishermen must take care.

"Make sure to get your shot all set up before taking the fish out of the water," she advised. "When you do take the fish out of the water, try holding your breath. When you need to breathe, the fish probably does too and it's time to put it back in the water."

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