ScienceDaily 9 Sep 08;
Nearly 40 percent of fish species in North American streams, rivers and lakes are now in jeopardy, according to the most detailed evaluation of the conservation status of freshwater fishes in the last 20 years.
The 700 fishes now listed represent a staggering 92 percent increase over the 364 listed as "imperiled" in the previous 1989 study published by the American Fisheries Society. Researchers classified each of the 700 fishes listed as either vulnerable (230), threatened (190), or endangered (280). In addition, 61 fishes are presumed extinct.
The new report, published in Fisheries, was conducted by a U.S. Geological Survey-led team of scientists from the United States, Canada and Mexico, who examined the status of continental freshwater and diadromous (those that migrate between rivers and oceans) fish.
"Freshwater fish have continued to decline since the late 1970s, with the primary causes being habitat loss, dwindling range and introduction of non-native species," said Mark Myers, director of the USGS. "In addition, climate change may further affect these fish."
Most Vulnerable Groups
The groups of fish most at risk are the highly valuable salmon and trout of the Pacific Coast and western mountain regions; minnows, suckers and catfishes throughout the continent; darters in the Southeastern United States; and pupfish, livebearers, and goodeids, a large, native fish family in Mexico and the Southwestern United States.
Nearly half of the carp and minnow family and the Percidae (family of darters, perches and their relatives) are in jeopardy. Fish families important for sport or commercial fisheries also had many populations at risk. More than 60 percent of the salmon and trout had at least one population or subspecies in trouble, while 22 percent of sunfishes — which includes the well-known species such as black bass, bluegill and rock bass — were listed. Even one of the most popular game species in the United States, striped bass, has populations on the list.
Regions with the Most Troubled Fish
Regions with especially notable numbers of troubled fish include the Southeastern United States, the mid-Pacific coast, the lower Rio Grande and basins in Mexico that do not drain to the sea.
Hotspots of regional biodiversity and greatest levels of endangerment are the Tennessee (58 fishes), Mobile (57), and the southeastern Atlantic Slope river systems (34). The Pacific central valley, western Great Basin, Rio Grande and rivers of central Mexico also have high diversity and numbers of fish in peril, according to the report. Many of the troubled fish are restricted to only a single drainage. "Human populations have greatly expanded in many of these watersheds, compounding negative impacts on aquatic ecosystems," noted Howard Jelks, a USGS researcher and the senior author of the paper.
Degree of Trouble
Of fish on the 1989 imperiled list, 89 percent are either still listed with the same conservation status or have become even more at risk. Only 11 percent improved in status or were delisted. The authors emphasized that improved public awareness and proactive management strategies are needed to protect and recover these aquatic treasures.
"Fish are not the only aquatic organisms undergoing precipitous declines," said USGS researcher Noel Burkhead, a lead author on the report and the chair of the AFS Endangered Species Committee. "Freshwater crayfishes, snails and mussels are exhibiting similar or even greater levels of decline and extinction."
The authors noted that the list was based on the best biological information available. "We believe this report will provide national and international resource managers, scientists and the conservation community with reliable information to establish conservation, management and recovery priorities," said Stephen Walsh, another lead author and USGS researcher.
This is the third compilation of imperiled, freshwater and diadromous fishes of North America prepared by the American Fisheries Society's Endangered Species Committee.
Additional information is available at http://fisc.er.usgs.gov/afs/
Freshwater fish in N. America in peril, study says
Seth Borenstein, Associate Press Yahoo News 11 Sep 08;
About four out of 10 freshwater fish species in North America are in peril, according to a major study by U.S., Canadian and Mexican scientists.
And the number of subspecies of fish populations in trouble has nearly doubled since 1989, the new report says.
One biologist called it "silent extinctions" because few people notice the dramatic dwindling of certain populations deep in American lakes, rivers and streams. And while they are unaware, people are the chief cause of the problem by polluting and damming freshwater habitats, experts said.
In the first massive study of freshwater fish on the continent in 19 years, an international team of dozens of scientists looked not just at species, but at subspecies — physically distinct populations restricted to certain geographic areas. The decline is even more notable among these smaller groups.
The scientists found that 700 smaller but individual fish populations are vulnerable, threatened, or endangered. That's up from 364 subspecies nearly two decades ago.
And 457 entire species are in trouble or already extinct, the study found. Another 86 species are OK as a whole, but have subspecies in trouble.
The study, led by U.S. Geological Survey researchers, is published in the current issue of the journal Fisheries. Researchers looked at thousands of distinct populations of fish that either live in lakes, streams and rivers or those that live in saltwater but which migrate to freshwater at times, such as salmon that return to spawn.
Some vulnerable fish are staples of recreational fishing and the dinner plate. Striped bass that live in the Gulf of Mexico, Bay of Fundy and southern Gulf of St. Lawrence are new to the imperiled list. So are snail bullhead, flat bullhead and spotted bullhead catfish. Sockeye, Chinook, coho, chum and Atlantic salmon populations are also called threatened or endangered in the study. More than two dozen trout populations are considered in trouble.
About 6 percent of fish populations that were in peril in 1989, including the Bonneville cutthroat trout, have made a comeback, said lead author Howard Jelks of the U.S. Geological Survey. But one-third of the fish that were in trouble in 1989 are worse off now, said the Gainesville, Fla., biologist.
The study includes far more species and populations than those that are on the official U.S. government endangered species list.
Jelks said the number of species in trouble was close to double what he expected and that means people should be "considerably worried."
The biggest cause, Jelks said, is degraded freshwater habitat, both in quality and quantity of water for fish to live in. Invasive species crowding out native fish is also to blame, he said.
Fish "live in a freshwater habitat that's pretty much under assault by people," said Duke University marine biologist Larry Crowder, who wasn't part of the study. "Things are tanking all around us. When does it have to be bad enough to get people's attention?"
Many of the species in trouble or already extinct are small minnows and darters whose absence is little noticed, but they play a vital role in the food chain.
Hardest hit is Mexico where nearly half the fish species are in trouble. One in three species in the United States are in peril — up from about one in five in 1989. About 10 percent of Canadian species dwindled. In the United States, the most vulnerable populations are in the Southeast, not counting Florida.
In the U.S., 263 fish species are in trouble or are already extinct, and nearly 500 have no problems.
The number of fish species and subspecies in North America that went extinct rose from 40 to 61 since 1989.
Anthony Ricciardi, a McGill University biologist who was not part of the research, found that about 10 years ago freshwater extinctions were happening at a faster pace than on land or in the sea. And yet few people notice, he said.
"A lot of silent extinctions are happening," Ricciardi said. "What we're doing is widespread, it's pervasive and it's rapid."
On the Net:
The article in the journal Fisheries: http://www.fisheries.org/afs/docs/fisheries/fisheries_3308.pdf
An interactive map by the U.S. Geological Survey that shows status of fish populations in 80 different regions of North America: http://fisc.er.usgs.gov/development/map_object.html
