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~~ '.f ~" ~QIdeL ~ ~-~~~ '~ Iq ~3 /~ , ,,,~„~wp..,~.Y..w......., CHAP'rLR 30 NATURAL VS MANMADE BACKWATERS AS NATIVE FISH HABITAT Richard A. Valdez U.S. Fish and Wildlife Service YellowstoneNutiunal Park, Wyoming Edmund J. Wick Colorado State lJniversity Fort Collins, Colorado A BST RAC'1' Natural backwaters and embayments are important habi- tats for native fishes of the Upper Colorado River System. The protected Colorado squawfish, humpback chub and razorback sucker use these quiet areas during various life stages. Water developments in the system have prompted mitigation for habitat enhancement to favor and recover these species. This paper explores the feasibility of recreating backwaters and embayments as part of this enhancement. Side channels diked for flood control in ttie Yampa River demonstrate the feasibi- lity of recreating backwaters using existing riverine fea- tures. These function as natural backwaters which adult Colorado syuawfish occupy during runoff. They drain with descending flow and do not become refuges for predaceous and competitive non-native fishes. Natural embayments are important low-water habitats, especially for young Colorado squawfish and humpback chub after runoff. These are created naturally during high flows by eddies around channel obstruc- tions or stable slugreline features, and can be artificially created with appropriately placed wing dams and bank re- inforcements. Abandoned gravel pits flooded by the Colorado River near Grand Junction, Colorado have long been viewed as simulating backwaters for native fish habitat. Most contain water year around and are refuges for large numbers of competitive non-native fishes and a host of pathogens. They do not appear to benefit native species and should be sealed from the river, and managed as warn-water game fisheries and waterfowl sanctuaries. However, gravel pits constructed in midchannel islands, graded gently to flood during runoff and 51 ~)