WASHINGTON — 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 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 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 greater 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 live in lakes, streams and rivers or those that live in saltwater but which migrate to freshwater at times, such as salmon.
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, and Atlantic salmon populations also are called threatened or endangered. More than two dozen trout populations are considered in trouble as well.
