Endangered Colorado River basin fish (Continued)

	Razorback sucker (Xyrauchen texanus) One of the largest suckers in North America, the razorback sucker can grow to up to 13 pounds and lengths exceeding 3 feet. The razorback is brownish-green with a yellow to white-colored belly and has an abrupt, bony hump on its back shaped like an upside-down boat keel.
	The razorback sucker was once widespread throughout most of the Colorado River Basin from Wyoming to Mexico. In the upper Colorado River Basin, they are now found only in the upper Green River in Utah, the lower Yampa River in Colorado and occasionally in the Colorado River near Grand Junction. Small numbers of razorback suckers also have been found in Lake Powell at the mouths of the Dirty Devil, San Juan and Colorado rivers. In the lower Colorado River Basin, razorback suckers have been found primarily in Lake Mohave, with smaller numbers in the Colorado River below Hoover Dam. In the upper Colorado River basin, biologists believe the razorback population totals only about 500 adult fish, most of which are thought to be 25 or more years old. Though some of these adult fish reproduce in the wild, few of their young have survived. (Also see:razorback sucker feature story).
	These fish can spawn as early as age 3 or 4, when they are 14 or more inches long. Depending on water temperature, spawning can take place as early as November or as late as June. In the upper Colorado River basin, razorbacks typically spawn between mid-April and mid-June. These fish reportedly migrate long distances to spawn, congregating in large numbers in spawning areas. Razorback suckers have been known to live 40 years or more. According to university researchers, this fish species evolved more than 4 million years ago. (Also see: Historical perspective.) Status and distribution: Listed as endangered under federal law in 1991. Endangered under Colorado law since 1979. Protected under Utah law since 1973.

Recovery strategies:

Because so few of these fish remain in the wild, biologists have been actively raising them in hatcheries in Utah and Colorado. These hatchery-raised razorbacks are being stocked in the Colorado, Gunnison,Green and SanJuan rivers.

Endangered fish grow significantly faster in backwaters and wetlands than they do in the river channel. Wetland habitats are believed essential to survival of young razorback suckers and recovery of the species. For this reason, the Recovery Program also has launched a program to acquire access to riverside wetlands for endangered fish, especially razorback suckers. Managing non-native fish species also is important to limit predation on young razorback suckers.

Recovery goals:

According to a February 1997 draft recovery plan, the razorback sucker will be eligible for "down-listing" from endangered to threatened when there no longer is a threat of immediate extinction in the wild, when populations have been recovered in Lake Mohave and in the Green and Yampa rivers, and when two other populations have been recovered or established - one in the upper Colorado River basin and one in the lower basin.

The razorback sucker will be considered recovered after it already has been down-listed to threatened and after two additional populations have been recovered or established.

More specific recovery goals are under development and will be published in draft in the Federal Register in early 2001. The recovery goals consist of both demographic criteria and criteria to minimize or remove threats. The objective, measurable criteria are presented for both downlisting and delisting for each of the four endangered fishes throughout their range.

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