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7/14/2009 5:01:45 PM
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UCREFRP
UCREFRP Catalog Number
7304
Author
Tyus, H. M.
Title
Distribution, Reproduction, and Habitat Use of the Razorback Sucker in the Green River, Utah, 1979-1986
USFW Year
1987
USFW - Doc Type
Transactions of the American Fisheries Society
Copyright Material
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<br />, <br />",; ..~ <br /> <br />jCjf?7 <br /> <br />/\jUS <br /> <br />\ <br /> <br />Transactions of the American Fisheries Society 116: I II-I 16, 1987 <br /> <br />9730Lj- <br /> <br />Distribution, Reproduction, and Habitat Use of the <br />Razorback Sucker in the Green River, Utah, 1979-1986 <br /> <br />. <br /> <br />HAROLD M. TyUS <br /> <br />u.s. Fish and Wildlife Service, 1680 West Highway 40, Room 1210 <br />Vernal, Utah 84078. USA <br /> <br />Abstract. - Distribution, habitat use, and relative abundance of the rare razorback sucker Xy- <br />rauchen texanus were evaluated by the capture of 323 of the fish and by the use of radiotelemetric <br />data from six fish, Razorback suckers in the Green River were not uniformly distributed; they <br />were most abundant in flat-water sections, and none were collected in white-water canyons. Ra- <br />zorback suckers displayed spawning movements in spring, and three spawning reaches were iden- <br />tified by the collection of 101 fish in breeding condition. Larval razorback suckers were collected <br />downstream of the spawning reaches, but no juveniles were collected, indicating little or no suc- <br />cessful recruitment. Spawning preferences were deduced from the capture of S2ripe razorback <br />suckers, between May 3 and June 15, 1984, and between April 22 and June 5, 1986, over sand <br />and gravel substrates. Water temperatures at the points of capture ranged from 10 to 18OC, aver- <br />aging 15"C. Catch data suggested that the razorback sucker population is small, and that the species <br />is more rare than the endangered Colorado squawfish Ptychocheilus lucius. Low numbers, little <br />growth, and no apparent recruitment suggest that this species will disappear in nature as old fish <br />die and are not replaced. <br /> <br />The razorback sucker Xyrauchen texanus is en- <br />demic to the Colorado River basin and is one of <br />its rarest species (Tyus et al. 1982). Alth~is <br />species was once abundant and widely distributed <br />(Seethaler et al. 1979), its riverine existence is lim- <br />ited primarily to the upper Colorado River basin, <br />where it occupies the mainstem of the Green and <br />upper Colorado rivers (McAda and Wydoski 1980; <br />Tyus et al. 1982). Recruitment may be limited <br />because young razorback suckers have seldom been <br />found (McAda and Wydoski 1980; Wick et al. <br />1982). The razorback sucker remains in mainstem <br />reservoirs in the lower Colorado River, but those <br />stocks appear to be relict subpopulations of very <br />old individuals (Minckley 1983; McCarthy 1986). <br />Rigorous sampling of fish populations in the <br />Green and upper Colorado rivers was begun by <br />the U.S. Fish and Wildlife Service (FWS) in 1979 <br />to determine the distribution, abundance, and life <br />history requirements of endangered fishes. Data <br />collected during this work constitute the largest <br />current body of knowledge for the razorback suck- <br />er in its native riverine environment. I present <br />data collected by me and by FWS coworkers in <br />the Green River basin of Colorado and Utah from <br />1979 to 1986, in an effort to document the biol- <br />ogy, status, and habitat use of this unique species. <br /> <br />Methods <br /> <br />Collections. - Razorback suckers were collected <br />primarily by electrofishing, although a few were <br /> <br />also obtained in seine and trammel nets. Two main <br />sampling programs were employed: a "standard- <br />ized" program conducted from April to Novem- <br />ber 1979-1981 and a "spring" program conducted <br />only from April to June 1984-1986. Both pro- <br />grams covered the mainstem of the Green River <br />between river kilometers 512 and 35, or from Di- <br />nosaur National Monument (DNM) to a point 35 <br />km above the confluence of the Green and Col- <br />orado rivers (Figure 1). The standardized program <br />also included the lower 224 km of the Yampa <br />River and the lower 240 km of the White River. <br />The spring program extended another 40 km up <br />the Green River to the Yampa River (km 552) <br />each year and also included the mouths of major <br />tributaries. <br />The standardized sampling program incorpo- <br />rated a design that divided the mainstem of the <br />Green River into six relatively homogeneous sec- <br />tions on the basis of general river geomorphology <br />(A-F in Figure 1). Within each section, an 8.8-km <br />reach was selected from a table of random num- <br />bers. Habitats within two 0.8-km stations were <br />sampled for 1 d each, either by boat electrofishing <br />or with seines, trammel nets, and wire traps (de- <br />pending on gear suitability). Electrofishing was <br />conducted alongshore throughout the 8.8-km <br />reach. Sampling was done during prerunoff, run- <br />off, and postrunoff flows. <br />The spring sampling program incorporated only <br />alongshore electrofishing in the prerunoff period <br /> <br />111 <br />
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