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Last modified
7/14/2009 5:02:28 PM
Creation date
5/22/2009 4:43:05 PM
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UCREFRP
UCREFRP Catalog Number
6042
Author
Haynes, C. M., R. T. Muth and T. P. Nesler.
Title
Identification of Habitat Requirements and Limiting Factors For Colorado Squawfish and Humpback Chub.
USFW Year
1985.
USFW - Doc Type
Fort Collins, Colorado.
Copyright Material
NO
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<br />43 <br /> <br />DISCUSSION AND CONCLUSIONS <br /> <br />Based on these results and complementary studies (e.g., Tyus et ale 1981; <br />Wick et ale 983; Tyus 1984a, 1984b; Tyus and McAda 1984), Colorado squawfish <br />reproduction in Colorado appears restricted to reaches of the mainstem <br />Colorado Riv r (Mesa Co.) and lower Yampa River (Moffat Co.). In the <br />Colorado Riv r, spawning occurs above the Colorado-Utah state line to Clifton <br />(L. Kaeding, CRFP, pers. comm.); however, captures of ripe adults and YOY <br />collections ave failed to definitively identify spawning sites and more work <br />is needed. olorado squawfish spawning in the Yampa River is apparently <br />largely rest icted to the lowermost 32 km of Yampa Canyon in DNM (i.e., <br />Harding Hole to Yampa-Green River confluence); the majority of ripe adult <br />fish general y congregate at river km 26-32 (Haynes and Bennett, in press). <br />However, the drift-net collection of one larval Colorado squawfish at Harding <br />Hole in 1983 established that at least limited spawning occurred above this <br />site. <br /> <br />During t is study, Colorado squawfish spawning in both rivers was <br />estimated to have begun in early-late July and typically extended to late <br />July through early August. For all years studied in both rivers, spawning <br />coincided wi h decreasing flow and rapidly rising water temperature; maximum <br />mainchannel ater temperature always approximated or exceeded 20 C during <br />spawning. Dring 1980-1982 (Yampa River), the numbers of Colorado squawfish <br />YOY collecte were too low to make realistic evaluations relative to spawning <br />"intensity"; however, estimated spawning dates for 1983 and 1984 revealed <br />that while 1 mited spawning occurred as early as 11 July and 4 July, <br />respectively (mean water temperature=18-20 C, both dates), a peak in spawning <br />activity occ rred between 25 July-10 August (1983) and 13-23 July (1984) with <br />mean water t mperatures of 22-25 C and 22-23 C, respectively. Hamman (1981) <br />reported an ptimum spawning temperature range of 20-22 C under hatchery <br />conditions. The 1983 estimated peak in spawning activity coincided closely <br />with dates w en radio-tagged adult fish were active over the spawning areas <br />(H. Tyus, CR P, pers. comm). <br /> <br />~ <br /> <br />The role played by water temperature and flow in streams in influencing <br />fish reprodu tion and larval production/survival are inseparable, with flow <br />exerting a d terministic effect on water temperature. Water temperature has <br />been documen ed as an important, influencing factor for several aspects of <br />fish ecology including movement and spawning (Nikolsky 1963; De Vlaming <br />1972). Spa ing commences at a particular water temperature and may continue <br />as long as t at temperature is maintained. For example, Beamesderfer and <br />Bjornn (1980 observed that peak spawning of northern squawfish <br />(Ptychocheil s oregonensis) in Idaho coincided with water temperature of <br />10-15 C and pawning ceased at 16-18 C. They also observed a reduction in <br />spawning act vity following a storm-induced water temperature decline of <br />approximatel 5 C. This latter observation suggests that water temperature <br />is an import nt, regulating factor in Ptychocheilus reproduction. Flow <br />exerts a pro ound influence on fish life cycles and habitats (Nikolsky <br />1963). For xample, flow is important in regulation of the areal extent and <br />preparation/ intenance of spawning and nursery areas, and influences the <br />extent and p ttern (spatial and temporal) of larval fish dispersion from <br />spawning are s. Depending on the mode of reproduction (e.g., lithophilic or <br />pelagophilic , several studies have reported variable responses of year-class <br />strength of iverine fishes to variations in discharge (Turner and Chadwick <br />
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