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.
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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 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, he said.