Lake Powell Chronicle | The Colorado River’s humpback whale chub has been downgraded from Endangered to Endangered

The humpback whale, one of four endangered fish in the Colorado River and its tributaries, is now an “Endangered” species instead of “Endangered”.

The status will take effect on November 17th.

“We are reclassifying the humpback whale chub from Endangered to Endangered (i.e. ‘downlisting’) because we have determined that the species is no longer critically endangered in all or a significant portion of its range,” said Matt Hogan , acting regional director for the US Fish and Wildlife Service.

According to the Federal Law on Endangered Species, a species is endangered if “there is a risk of extinction in all or major parts of its range”. An “endangered” species is likely to be endangered in the “foreseeable future”.

After doing a “thorough review of the best scientific and commercial information available,” the USFWS determined that the fish was no longer endangered throughout its range as only one in six original populations increased. Of the original six populations that existed in 2002, one has now become extinct.

Along with the Humpback Chub, the Colorado Pikeminnow, Bony Tail Chub, and Razorback Sucker were originally classified as endangered due to habitat loss from the construction of multiple dams. Climate change has now made the situation worse. Only the humpback whale chub was added to the downlist.

The humpback chub, which has developed in warm, muddy waters, usually grows to a maximum size of around 20 inches and 2.5 pounds.

In the Grand Canyon, chub growth is stunted by the cold water flowing from Glen Canyon Dam and only does well in the warmer waters of the Little Colorado River.

The humpback whale is a member of the minnow family, and by minnow standards, it is considered a large fish dwarfed by the Colorado pikeminnow. Under normal conditions, a humpback whale can survive in the wild for more than 30 years.

The humpback whale chub was first classified as endangered in 1967. Its numbers began to decline shortly after three dams were built to drain the Colorado River: Glen Canyon, Hoover and Flaming Gorge.

Originally, six populations were identified that were confined to the Colorado River and three of its tributaries: the Green and Yampa Rivers in Colorado and Utah and the Little Colorado River in Arizona.

According to 2002 USFWS data, an estimated 2,000 to 3,000 adults lived in the Black Rocks and Westwater canyons in the Colorado River near the Colorado-Utah border. It is estimated that several hundred to more than 1,000 adults lived in Desolation / Gray Canyon in the Green River.

The populations in the Yampa and Cataract canyons were small, each consisting of up to a few hundred adults. According to the Center for Biological Diversity, the Yampa population has since become extinct, leaving five populations today.

The largest population of humpback whales is found in the Grand Canyon in the Little Colorado River and its confluence with the main trunk of the Colorado River.

In 2009, the US Geological Survey announced that that population in the Little Colorado River had increased to between 6,000 and 10,000 adults between 2001 and 2008, the only population to show an increase.

Recently there was a proposal to build two dams in the Little Colorado River canyon, but those projects have not advanced, in part because of the presence of the chub. Instead, proposals to pump out wells in Little Colorado’s drainage remain, making the future of the chub uncertain.

The chub’s deadly enemy is the black bass, an alien species that thrives in the rivers above Lake Powell. Perch have not yet established themselves in the Colorado River below the Glen Canyon Dam. As reservoir levels sink, the river in the Grand Canyon will likely make it warmer and more habitable for the smallmouth bass.

Instead, the brown trout threatens the humpback whale. Brown trout are not native and are increasing in number, accounting for approximately 25% of current trout catches in the Lees Ferry area.

The rest are rainbow trout, which are considered a less serious threat to the chub. Glen Canyon NRA continues to pay a reward to anglers who catch and kill brown trout, but so far, politics has not suppressed their numbers.

Other ways to help the humpback whale, discussed by a technical group advising the government on the management of the Glen Canyon Dam, is to build hydropower turbines in the dam’s bypass tubes to provide colder water from the depths of Lake Powell the Grand . Canyon can flow down if necessary.

However, this would reduce the capacity of the bypass pipes if they were needed, as it did in 1983 when Lake Powell exceeded the construction height of 3,700 feet.

With only one population of five remaining humpback whale populations on the rise, some are questioning the wisdom of a downlisting.

In a press release dated January 21, 2020, the Center for Biological Diversity said that “the (US Fish and Wildlife Service) looked only 40 years into the future when it came to deleting the chub, although climate models extend to 2100 and paint a bleak picture the availability of water in the Colorado River. “

Alicyn Gitlin, program manager for the Sierra Club’s Grand Canyon, said, “This is a political choice, not an environmental choice.”

The threatened status still prevents people from killing it and holds the weight of the Endangered Species Act behind conservation. Should an angler accidentally catch a humpback whale, it is expected that the fish will be carefully removed from the hook and returned to the river.

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