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Brazil Goes Fishing -- and Catches New Species

Natural barriers allowed some fish to evolve differently. Researchers fear forest destruction is robbing rivers of nutrients.

June 08, 2003|Michael Astor | Associated Press Writer

RIO DE JANEIRO — It's not the case of the one that got away but of thousands of fish that until now escaped scientists' grasp. A new study shows Brazil -- thought to have the world's greatest variety of freshwater fish -- has more than twice as many species as once thought.

It was estimated the massive rivers and flood plains were home to 1,300 species, but a six-year survey nearing completion has cataloged nearly 3,000. By comparison, the United States has about 790 species and China is estimated to have 700 to 800.

Scientists found entirely new species -- including one with a quirky way of luring female fish. But they found their work was more urgent because Brazil's fish are vanishing at an alarming rate due to forest destruction that robs rivers of nutrients.

"How can we know what needs to be preserved if we don't even know how many species exist?" said Naercio Menezes, a professor at the University of Sao Paulo who coordinated the government-funded survey.

The study also examined Brazil's Atlantic coast, but turned up fewer surprises because saltwater species are better known.

Since 1997, researchers from four Brazilian universities have conducted more than 30 expeditions to rivers, lakes and streams in the nation's heartland, collecting some 50,000 specimens.

The surprises began when scientists started adding up the number of species documented by researchers working separately throughout Brazil -- something no one had done before. The number was more than double what had been believed.

But the survey also found hundreds that were unknown to science. Menezes estimated the number new species at 10% to 15% of the total. Researchers expect the final tally to take years because of the time required to describe and catalog new species.

A scientific description of one new species, Hyphessobrycon heliacus, has already been published in the scientific journal Copeia. The fish is a golden-colored tetra, just 1.26 inches long, with yellowish-red fins and a large black spot on its tail.

Another as-yet-unnamed species, a tiny bluish fish measuring about 1.5 inches, is to be described in the scientific journal Proceedings of the Biological Society of Washington.

Scientists say the species is unique because the sexually active males have a special gland on their anal fin that secretes pheromone, a substance that excites females during courtship.

No other known species has such a gland on that fin, said Stanley Weitzman of the Smithsonian Institute in Washington, D.C., who is a co-author of the fish's scientific description.

Weitzman said one reason for the diversity in Brazil is its varied geological and climatic history. Isolated by elevation and accompanying temperature differences, fish were separated by natural barriers that allowed species to evolve differently over thousands of years.

"Some waters are acid; others are neutral or somewhat alkaline," he said. "There are so many tributaries to the Amazon River, many with a different ecology."

Researchers concentrated on the headwaters of little-studied rivers in Brazil's interior. Given the nation's sheer size -- larger than the 48 continental United States -- they believe many species remain to be discovered.

But the study also suggested what scientists had feared: A number of species may have disappeared for good, victims of pollution and deforestation.

"We have to document what exists as rapidly as possible," Menezes said. "We are convinced there are species that have already disappeared without being scientifically described."

The inventory, being put on the Internet, will allow users to create maps showing where the fish live. Researchers hope that the documented existence of rare species will encourage policy-makers to preserve them.

"There's a very direct link between the health of the forests and the number of fish in the rivers," said Paulo Buckup of Rio de Janeiro's National Museum, who is in charge of putting the catalog on the Internet.

He said the number of species in a well-forested area can easily reach 80, dropping dramatically to just four or five in an area where the surrounding forest has been cut down. The loss of forests changes the alkaline balance in the rivers, he said. Some fish also live on the fruit that drops from trees and when the trees are gone, they starve.

The expansion of agriculture has hurt the fish population as pesticides kill insects that are an important food source.

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