Fish conservationists saved wrong species

c8ba9e6b-443d-44d0-82fd-7250de72c012

Editor's Picks
Features Post
The brightest pupils
04 October 2021
Features Post
Dealing with egg ‘fungus’
04 October 2021
Features Post
Rathbun’s tetra in the wild
13 September 2021
Fishkeeping News Post
Report: 2021 BKKS National Koi Show results
13 September 2021
Features Post
The World's forgotten fishes
16 August 2021


Scientists who have been trying to preserve an endangered species of fish for the past two decades have learned that they were preserving the wrong species.

Fisheries biologists attempting to preserve the endangered Greenback cutthroat trout, Oncorhynchus clarkii stomias, were successful in rearing thousands of fish over the past 20 years and stocking them in Colorado's rivers, lakes and streams.

However, a new molecular study by scientists from the University of Colorado at Boulder has provided evidence to suggest that, in most cases, the fisheries biologists had been working with a closely related species and not the true Greenback cutthroat trout.

The findings, which are published in the latest volume of the journal Molecular Ecology, are based on a study using molecular markers from the mitochondrial and nuclear genomes of the fish.

The results show that rather than conserving the endangered Greenback cutthroat trout, Oncorhynchus clarkii stomias, the fisheries biologists were actually rearing the closely related Colorado River cutthroat trout, Oncorhynchus clarkii pleuriticus.

Risk of extinctionLead author of the paper, Jessica Metcalf, a researcher at Colorado University's department of ecology and evolutionary biology, said that eggs and sperm from the fish had been used for the several decades to rear new generations of fish for restocking.

The findings show that the majority of the trout has been misidentified, so fisheries biologists were conserving the wrong subspecies.

Metcalf believes that the existing range of the Greenback cutthroat trout might now be just an 11-mile stretch of streams in several remote areas of Colorado.

"Our results suggest greenback cutthroat trout within its native range is at a higher risk of extinction than ever before despite conservation activities spanning more than two decades", said Metcalf.

MisidentificationThe problem is believed to have been caused by misidentifications dating back to the stocking of trout in Colorado waters in the late 1800s and early 1900s.

Metcalf says that hundreds of thousands of baby trout of various subspecies were spread around Colorado waters for fishing: "This illustrates the need for biologists to consider that the species may have been introduced by the industriousness of humans before the documentation of the native flora and fauna of the area was recorded."

The Greenback cutthroat trout was declared extinct in the wild in 1937, due to mining pollution, fishing and competition from other species of trout. However, several small populations were discovered years later and a programme was started to conserve the endangered fish.

"We have to remember that management decisions by federal and state fisheries biologists over the past decades were based on the best reports available by experts at the time," said Metcalf.

"Fortunately, the data is becoming more accurate over time as genetic techniques improve and the peer review process is increasingly incorporated into scientific management strategies."

For more information see the paper: Metcalf JL, Pritchard VL, Silvestri SM, Jenkins JB, Wood JS, Cowley DE, Evans RP, Shiozawa DK, Martin AP (2007) - Across the great divide: genetic forensics reveals misidentification of endangered cutthroat trout populations. Mol Ecol. 2007 Aug 28.