At least five of the 22 fish identified could become nuisances and disrupt the current balance of fish in the Great Lakes, said Cynthia S. Kolar, a research fishery biologist for the U.S. Geological Survey Upper Midwest Environmental Sciences Center. She is first author of a study appearing Friday in the journal Science.

“A lot of fish in the Caspian can live in marine salinities all of the way up to fresh water,” said Kolar. This means they could easily adapt to the Great Lakes.

Alien fish are common in the U.S. Some are used as bait by sport fishermen, while others were pets that were released into U.S. waters. For instance, the northern snakefish, a voracious predator that can live out of water and quickly multiply, was introduced into a Maryland pond by a pet owner. State biologist poisoned the pond last summer to wipe out the invader.

Kolar said most of the alien species introduced into the Great Lakes arrive in the water that ships carry in ballast tanks. Ships take on tons of water in the Caspian or Black Seas for stability while crossing the Atlantic, and larvae or baby fish are sucked in. When the ships dump their ballast in the Great Lakes, they also dump the alien species.

Kolar said that understanding which fish could represent threats to the Great Lakes could help policy-makers draw up new regulations controlling ballast dumping by ships. Right now, ships bound for the Great Lakes are required to make a mid-ocean exchange of ballast water, a measure aimed at reducing the transfer of alien species. More stringent measures may need to be considered, she said.

Some introduced species have been devastating. The U.S. and Canada spend about $15 million a year to control the lamprey, a snakelike bloodsucker that attaches itself to larger fish. The lamprey almost drove the native lake trout to extinction when it first expanded into the Great Lakes, said Kolar.

Another introduced species is the zebra mussel, a fast growing filter-feeder that clings to boats and pilings and jams water intake pipes. Combatting the pesky mussel in the Great Lakes costs the U.S. about $100 million a year, said Kolar.

Some alien species were at first a nuisance and then a benefit, she said. The alewife, a small forage fish, invaded the Great Lakes and exploded in population. Some Pacific salmon species were then introduced to control the alewife, and now fishing for the salmon has become a recreational industry, said Kolar.

Until now, scientists could only guess which alien fish were likely to be introduced into the Great Lakes and which would thrive there.

The study by Kolar and by David M. Lodge of Notre Dame identifies the Caspian and Black Sea species that may become a nuisance in the Great Lakes.

Among the likely nuisances are the tyulka, a shad-like fish already invading European rivers; the Eurasian minnow; the Black Sea silverside; the European perch; and the monkey goby.

“No one knows for sure if the forage fish would be ideal or have a long-term negative effect,” said Kolar, “but these potential bait species (such as the silverside and minnow) could really hurt the native fish.”

The European perch, she said, could outcompete the native yellow perch and change the ecology of the Great Lakes. The round goby, a trash fish which is a relative of the monkey goby, is already troublesome.

“They are really abundant and are considered a nuisance by fishery managers because they are constantly being caught on hooks” intended for other species, said Kolar.

November 7,2002

TopicID: 233

In parallel efforts that involved more than 160 researchers in 10 countries, scientists mapped the genes for Plasmodium falciparum, the deadliest form of malaria, and for Anopheles gambiae, a mosquito that prefers human prey and spreads malaria to millions with its bloodsucking bite.

The British journal Nature published the complete genetic sequence of P. falciparum. The mosquito genome is being published by the American journal Science. The achievement was announced today in London and in Washington.

“This is an extraordinary moment in the history of science,” said Carlos Morel of the World Health Organization. “At last, the enormous power of modern technology is penetrating the mysteries of an ancient disease … which continues to kill millions.”

Neil Hall of the Wellcome Trust Sanger Institute in the United Kingdom, one of the participating labs, said the gene map provides new molecular targets for vaccines and drugs.

“We have presented scientists with the haystack,” Hall said. “They have got to go out and find the needle.”

New drugs are desperately needed, said Stephen Hoffman, a co-author of the study who was a researcher at the Naval Medical Research Center in Silver Spring, Md.

Hoffman said all of the major drugs now in use are very old and their effectiveness is fading rapidly.

“The drugs that we use to treat malaria were introduced 50 to 2,000 years ago,” said Hoffman.

He said German researchers already are developing a drug they first tested after spotting a genetic vulnerability in one chromosome of the parasite.

Frank H. Collins, a mosquito expert at Notre Dame University, said studies of the Anopheles gambiae genome have revealed genes that may explain why the mosquitoes favor humans above all other prey.

He said genes linked to the insect’s sense of smell may be exploited to develop new repellents, while other genes may lead to novel insecticides.

Completing the gene mapping of malaria and the mosquito comes at a critical time in international public health, officials said. 91��Ƶ show malaria is becoming increasingly resistant to chloroquine, a drug that has held the line against the disease for decades. At the same time, the mosquito has become tougher to control with current insecticides.

The advances also come in an era when some experts fear a warming climate will let the resistant malaria parasite move into areas where it has been rare or unknown. Malaria, though of a different strain, was detected in both humans and mosquitoes in Virginia recently, the first time in two decades that a wild reservoir of malaria has been found in this country. Hoffman said 300 million to 900 million people are infected with malaria each year, including 10,000 to 30,000 travelers who visit malaria-infested areas and return home with the disease.

The mosquito is a key part of the three-stage life cycle of the malaria parasite.

The female A. gambiae requires a blood meal to mature its eggs. An insect infected with malaria injects the parasite into a human when it sucks up blood. The parasite invades first the liver and then red blood cells. When another mosquito bites, parasites transfer into the new insect, which then bites another human and the cycle begins anew. Malaria causes chills and fever, with temperatures rising to 105 or higher, often with headaches, muscle pain and vomiting. Repeated attacks can cause death.

OCT. 3, 2002

TopicID: 228