In response to a petition by a conservative legal group, the U.S. Fish and Wildlife Service wants to remove a small fish that lives in only a few streams in California and Oregon from the Endangered Species List.
First listed as Endangered in 1985, the Modoc sucker (Catostomus microps) is a three-inch fish that lives in tributaries of the Pit River and Goose Lake in northeastern California and south-central Oregon. USFWS is suggesting that a program of livestock exclusion from watersheds, along with discoveries of previously unknown populations of the sucker, justify removing the species from protection under the federal Endangered Species Act.
The proposal comes in response to a 2011 petition by the Pacific Legal Foundation that asked USFWS to act on its own recommendation in 2009 that the sucker be "downlisted" from Endangered to Threatened.
When it was first listed in 1985, the fish was down to fewer than 1,300 known individuals of pure genetic stock, along with about twice that many hybrids with the related Sacramento sucker. Hybridization was and is seen as a major threat to the species, and cattle grazing was a major indirect cause of that genetic swamping. Erosion from grazed slopes in the Modoc suckers' home watersheds changed the structure of the creeks, removing barriers to reproduction between the two species. It also reduced water quality in the sucker's streams, depriving the fish of the algae, invertebrates and organic matter they eat.
Installing cattle exclusion fences has worked to limit that erosion, according to USFWS. And the discovery that previously taxonomically ambiguous sucker populations in Oregon streams flowing into Goose Lake turned out to be closely related enough to California's Modoc suckers to be assigned to the same species further supports a finding that the species has "recovered," according to USFWS's Proposed Rule delisting the sucker, to be published tomorrow in the Federal Record.
Conservation groups may well challenge a total delisting of the species. Among other things, the sucker's stream habitat is still vulnerable to damage from development, a recent example being the Ruby natural gas pipeline built in 2011 through the sucker's Oregon range, which a federal court judge had earlier ruled posed a risk to the sucker and four other endangered fish species.
Modoc suckers tend to inhabit water that's mid-way between being cold-water trout pools and warm shallows. They prefer streambeds ranging from fine silt to small gravel, and tend to stay under cover of overhanging branches and tree roots, or among streamside vegetation. Some adults have reached lengths of six inches, but three inches or shorter is much more common. Populations in the Pit River and Goose Lake drainages were separated from one another starting in the 19th century, when water diversions for agriculture and other human pursuits ended occasional floods on the Pit River that would overflow into Goose Lake.
The Proposed Rule, when published Thursday, will launch a 60-day public comment period on the delisting, after which USFWS may make a final decision.