USGS: North American Fish Extinctions May Double by 2050

GAINESVILLE – From 1900-2010, freshwater fish species in North America went extinct at a rate 877 times faster than the rate found in the fossil record, while estimates indicate the rate may double between now and 2050. This new information comes from a U.S. Geological Survey study to be published in the September issue of the journal BioScience.

In the fossil record, one freshwater fish species goes extinct every 3 million years, but North America lost 39 species and 18 subspecies between 1898 and 2006. Based on current trends in threatened and endangered fish species, researchers estimate that an additional 53-86 species of freshwater fish may be extinct by the year 2050. Since the first assessment of extinct North American freshwater fishes in 1989, the number of extinct fishes increased by 25 percent.

"This study illustrates the value of placing current events into the context of deep geologic time, as rocks preserve an unbiased record of natural rates of processes before human activities began to alter the landscape, the atmosphere, the rivers, and oceans," said USGS Director Marcia McNutt. "Freshwater fish are a good choice for analysis as their bones make clear fossil impressions, and their lake and river environments produce excellent stratigraphic sequences."

The study's author, Noel Burkhead, used an established method to compare the rate of extinction found in the fossil record with modern rates.

"Estimates of freshwater fish extinctions during the twentieth century are conservative, because it can take 20-50 years to confirm extinction," said Burkhead, a research fish biologist for the USGS. Extinction is a natural process, Burkhead explained, so examining its rate over a long geological timescale provides biologists with a benchmark for comparing current extinctions to background rate. The accelerated pace of extinction observed since the beginning of the twentieth century suggests human causes.

In North America, assessments of extinctions are conducted by the American Fisheries Society's Endangered Species Committee, using categories to factor in a lag time since the last observation of the species. The study used the categories "extinct" (species not seen for 50 years or more), "possibly extinct" (not been seen for 20 years or more), and "extinct in nature." All these categories require that searches for the missing fishes must have been made by knowledgeable biologists.

...

A summary of data on extinct North American freshwater fishes is available online on the Extinct North American Fishes website, which is updated by USGS and the AFS. Putting the numbers into perspective:

• 39 — Number of North American freshwater fish species confirmed as extinct from 1898 to present
• 1213 — Number of freshwater fish species found in North America up until 2010
• 3,000,000 — Average number of years between each fish extinction documented in the fossil record
• 2006 — Year that the most recent fish extinction was confirmed
• 31,769 — Total number of valid fish species described worldwide up until 2010
• 43 — Percent of the world’s fish species that depend on freshwater habitats