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7/14/2009 5:01:47 PM
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UCREFRP
UCREFRP Catalog Number
8168
Author
McAda, C. W. and L. R. Kaeding.
Title
Movements of Adult Colorado Squawfish During the Spawning Season in the Upper Colorado River.
USFW Year
1991.
USFW - Doc Type
Grand Junction, Colorado.
Copyright Material
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kAb <br />Transactions of the American Fisheries Society 120:339-345, 1991 <br />Movements of Adult Colorado Squawfish during the <br />Spawning Season in the Upper Colorado River <br />CHARLES W. MCADA AND LYNN R. KAEDINGI <br />U.S. Fish and Wildlife Service, Colorado River Fishery Project <br />529 25th Road, Suite B-110, Grand Junction, Colorado 81505, USA <br />Abstract. -Colorado squawfish Ptychocheilus Lucius spawned in widely separated areas through- <br />out the 350-km section of the upper Colorado River upstream from Lake Powell, Utah, as evi- <br />denced by the movement of radio-tagged adults during the spawning season and the later capture <br />of larvae. With one exception, tagged fish remained separated from each other during the spawning <br />season. Distances moved by tagged fish were not related to fish size or location of initial capture <br />along the river. Movements were generally shorter (mean, 23.2 km) than those reported for this <br />species in the Green River basin, in part because of important habitat differences between the two <br />rivers. Most tagged. Colorado River fish were found near their initial point of capture after the <br />spawning season. <br />The Colorado squawfish Ptychocheilus lucius, a <br />large piscivorous cyprinid endemic to the Colo- <br />rado River basin, has been presumed to make sea- <br />sonal, often long-distance migrations to discrete, <br />widely separated river reaches to spawn; its larvae <br />are believed to drift to nursery areas far down- <br />stream (Tyus 1986). Such life-history character- <br />istics have implications for management to pro- <br />tect and enhance the habitats and populations of <br />this endangered species. Blockages of fish move- <br />ment, for example, can decimate populations of <br />obligate migratory fishes, as demonstrated by Co- <br />lumbia River dams and Pacific salmons Onco- <br />rhynchus spp. (Netboy 1974). For this reason, it <br />was important to determine whether the life his- <br />tory proposed by Tyus (1986) for Colorado <br />squawfish in the Green River basin is generally <br />applicable to this species. The objective of our <br />study was to describe the movements of adult Col- <br />orado squawfish during the spawning season in the <br />upper Colorado River. <br />Study Area <br />The study was conducted in the 350-km reach <br />of the Colorado River between Lake Powell, Utah, <br />and Palisade, Colorado (Figure 1). Locations along <br />the river were demarcated as river kilometers (RK) <br />upstream or downstream from the confluence with <br />the Green River (RK 0). The study area was di- <br />vided into eight reaches (Figure 1) defined largely <br />by the occurrence of major tributaries, barriers to <br />upstream movement, or prominent changes in <br />'Present address: U.S. Fish and Wildlife Service, Yel- <br />lowstone Fishery Assistance, Post Office Box 184, Yel- <br />lowstone National Park, Wyoming 82190, USA. <br />river morphometry. Cataract and Westwater can- <br />yons were not sampled because of logistic diffi- <br />culties. Reach 8 is a short (4-km) segment of the <br />Gunnison River downstream from the Redlands <br />Diversion, a barrier to the upstream movement <br />of fish. <br />Methods <br />Larval fish. -Larval Colorado squawfish were <br />used to estimate the spawning period. We sampled <br />larval Colorado squawfish (6-24 mm total length, <br />TL; Snyder 1981) in reaches 2 through 7 during <br />July and August 1982 and from July to September <br />1983, 1984, and 1985. Colorado squawfish spawn <br />during these months in the upper Colorado River <br />(Haynes et al. 1984). Each of reaches 2-7 was sam- <br />pled at about 2-week intervals; reaches 1 and 8 <br />were sampled less frequently. We used 0.5-mm- <br />mesh seines (0.9 x 0.9 m) to collect larval fish <br />from low-velocity shoreline areas (e.g., backwa- <br />ters, eddies, pools) at about 8-km intervals along <br />the river. Collection of each sample required 5- <br />15 min. All larval fish collected were fixed and <br />preserved in 5% formalin and later identified and <br />counted at the Larval Fish Laboratory, Colorado <br />State University, Fort Collins. Colorado squaw- <br />fish larvae were measured to the nearest milli- <br />meter (TL). <br />We estimated hatching dates for individual Col- <br />orado squawfish larvae by back-calculation with <br />an equation developed by Haynes et al. (1985) for <br />the growth of age-0 Colorado squawfish in a <br />hatchery at about 20°C (Hamman 1981): <br />339 <br />AGE = -76.7105 + 17.4949 TL <br />-1.0555 TL2 + 0.0221 TV
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