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RECOVERY PRffiRAM FOR THE ENDANGERED FISHES ~OF THE UPPER COIORAID Spring 1991 Razorback sucker on verge of extinction? Biologists in upper Colorado River Basin find 20-year-old fish, but no young By Connie Young Public Information Specialist Colorado DiVision of Wildme The razorback sucker, a fIsh that evolved more than 4 million years ago in the Colorado River system. may be headed for extinction in the wild. The only wild razortJacks left are 20 or more years old. say biologists worldng with these rare fish. Since the 1960s. no young razortJacks - except for an occasional fIsh found shonty after they were stocked - have been found in the upper Colorado River or its tributaries upstream of Lake Powell. "We've been collecting ra1.OIbacks for 11 years, and we've never seen a juvenile," .,..dO ..,...;:,......,.....;:....... ...............,..,. ....,....,..... ..... ..,.... ":..:::.:.. ..:............. ...............,.,......... ...". :...': ..~.. .:,"... .. said Harold Tyus, leader of the U.S. Fish and Wildlife office in Vernal. Utah. Tyus and other biologists studying the fIsh find fewer adult razorbacks every year. Between 1979 and 1982, researchers working on the ColoradO River near Grand Junction. Colo., found between five and 30 adult razorback suckers during annual surveys. But between 1985 and 1988, they found only two to fIve fish each year. (No surveys were done in this area in 1983 and 1984.) "It's really hard to find razorbacks (in the Colorado River) anymore," said Doug Osmundson, a biologist with the fish and Wtldlife Service in Grand Junction. Habitat changed by floods floods in 1983 and 1984 washed out key "backwaters" in the Colorado River. Also, some landowners formed dikes along riverbanks to pre- vent flooding onto fann land. This eliminated the isolated pools that had fonned during periods of high river flows. Biologists believe razorbacks had used these protected backwaters and pools during the spawning season. "Since then, we've found no more than five razorbacks in a single year. and all have been adults. Osmundson said." :,. '!]I;;'.... ." ~,",,, ' ,., 'F ':.:~;.~~'. ~~ Pholo by Calhy Karp U.S. Fish and Wildlife Service volunteer Myron Chase holds a s-pound female razorback sucker captured In the lower Yampa River In 1988 as pan of research on this rare fish. BIOlogists collected eggs from the fish before releasing It unhanned back Into the river. That means that. unless new recovery steps are taken, as the adults die off, eventu- ally so will the entire popula- tion. Razorback suckers were once widespread throughout most of the Colorado River system from Wyoming to Mexico. Now, they are foWld in only seven locations. In the upper Colorado River Basin (above Lake Powell), the largest population is in Utah's upper Green River. Others in the upper basin are in the San Juan River and in the Colorado River near Grand Junction. One of the largest suckers in North America. the razor- back is listed as endangered under Colorado and Utah state laws and has been pro- posed for federal listing under the Endangered Species Act. The decision will be published in the Federal Register, probably in May 1991. Offspring don't survive In the Green River, biolo- gists still find razorbacks in spawning condition. but apparently something keeps their offspring from surviv- ing. The eggs may be eaten by other fish, or young razor- See RAZORBACK. page 8