Fishes that once were abundant in North American streams, rivers and lakes are now disappearing, with nearly 40 percent of all species in jeopardy, according to the most detailed assessment of the conservation status of freshwater fishes in the last 20 years.
The report shows that 61 fishes are presumed extinct, and 280 species are classed as endangered. In addition 190 are considered threatened, and 230 fishes are listed as vulnerable to extinction.
The new report, published in the journal “Fisheries,” was conducted by a team of scientists from the United States, Canada and Mexico, led by scientists from the U.S. Geological Survey. The team examined the status of continental freshwater fishes and those that migrate between rivers and oceans.
“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.”
The 700 fishes now listed as imperiled for this report by the Endangered Species Committee of the American Fisheries Society are a 92 percent increase over the 364 listed in the previous 1989 study.
The fish at greatest risk are the salmon and trout of the Pacific Coast and western mountain regions. More than 60 percent of the salmon and trout had at least one population or subspecies in trouble, the report shows.
Also at great risk are 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.
Fish families important for sport or commercial fisheries are also vulnerable to extinction. One of the most popular game species in the United States, striped bass, has populations on the list.
Twenty-two percent of sunfishes, a family which includes the well-known species such as black bass, bluegill and rock bass, are listed as at risk.
The southeastern United States, the mid-Pacific coast, the lower Rio Grande and basins in Mexico that do not drain to the sea are losing their freshwater fish species more quickly than other regions.
“Human populations have greatly expanded in many of these watersheds, compounding negative impacts on aquatic ecosystems,” said Howard Jelks, a USGS researcher and the senior author of the paper.
River systems that are both hotspots of regional biodiversity and also show the greatest levels of endangerment are the Tennessee, where 58 fishes are in jeopardy; the Mobile with 57 fishes at risk; and the southeastern Atlantic Slope river systems where 34 fishes are imperiled.
The Pacific central valley, western Great Basin, Rio Grande and rivers of central Mexico also have high diversity and numbers of fish at risk of extinction, according to the report.
Many of the fish populations at risk are restricted to only a single drainage.
Of fish on the American Fisheries Society’s 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 say the new list is 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.
The authors emphasize that improved public awareness and proactive management strategies are needed to protect and recover these and other aquatic species.
“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.”