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Last modified
7/14/2009 5:01:45 PM
Creation date
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UCREFRP
UCREFRP Catalog Number
7335
Author
Valdez, R. A. and E. J. Wick
Title
Natural Vs Manmade Backwaters as Native Fish Habitat
USFW Year
1983
USFW - Doc Type
\
Copyright Material
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fields, and inadvertently created desirable native fish <br />habitat. These backwaters are usually short-lived; they fill <br />at spring runoff in May and drain with descending flows in <br />late June or early July. <br />One such backwater is located at river mile (RM) 59, <br />just above Cross Mountain Canyon. The dike prevents a side <br />channel from flowing and a backwater is formed by waters <br />rising from the downstream end (Figure 3). The feature is <br />about 1.5 ha in surface area and is 0.3-1.5 m deep, with a <br />silt substrate. Two radiotagged Colorado squawfish, tagged <br />46 and 62 km upstream in early May, entered this backwater at <br />peak runoff in early June 1981. Both fish freely swam the <br />length of the backwater and periodically stayed at the <br />outlet near the flooding river. The backwater, at this time, <br />had relatively silt-free water and was warmer than the <br />torrential river. One fish spent nearly 2 weeks in the <br />backwater before moving downstream. One week after the fish <br />left, the water level receded sufficiently to isolate the <br />backwater from the river. <br />.e _ .~.-_ <br />f ; R. rw~1 a'~ ~ ~ .~ ~...- .. <br />,,,r- __ ,~, -~ .. <br />- ~. <br />~s ~ ..- <br />-,;. ..,. <br />uw. ` ~ <br />_ . ~a ± <br />y <br />- .;.-.DJ y ~Si " _ <br />`VIM--.r _ ~X ~~y ! _ <br />.tea .c ~ ~,, T ~ ° .~ <br />Y_ f~` <br />rcL... .Y:: SI ... .. _ . Y'.. .. ... .. . <br />Figure 3. Aerial view of side channel on the Yampa River <br />diked for flood and erosion control at river mile <br />59. The backwater formed by the large earthen <br />dike is sealed from the main channel at low flow. <br />A second diked side channel at RM 99, above Juniper <br />Canyon, was also used by two radiotagged squawfish during <br />runoff in early June 1981. This feature was about 1.5 m deep <br />with a silt bottom and a 1-m deep narrow channel leading to' <br />the river. The feature was drained by descending flows in <br />late June, about 1 week after the squawfish left. <br />A side channel at RM 64, diked to protect a low-laying <br />alfalfa field, also developed into a backwater during runoff. <br />Maximum depth was 1.5-2.0 m and the backwater was drained by <br />descending flows in late June. One radiotagged squawfish <br />entered this backwater briefly in mid -June for the high-flow <br />period then proceeded downstream and entered the large <br />backwater previously mentioned at RM 59. <br />A natural backwater in this same area of the Yampa <br />River was also used by these fish, suggesting that adult <br />radio-tagged Colorado squawfish showed a strong tendency to <br />find and occupy natural and manmade backwaters during runoff <br />1981 in [he Yampa River. The capture of numerous squawfish <br />in large backwaters of the Colorado River during runoff also <br />supports this contention. The flood control structures of <br />the Yampa River demonstrate that usable backwaters can be <br />intentionally created to enhance adult and possibly juvenile <br />squawfish habitat during high flows. <br />Design Backwaters <br />Fish habitat enhancement efforts were attempted in the <br />Upper Yampa River by private industry in the late 70's. Side <br />channels were diked to create backwaters like those described <br />in the previous section. But, the dikes were constructed of <br />rock instead of earth and eventually breached to allow either <br />continuous flow or flow only during runoff (Figure 4). The <br />side channels with dikes that breached at high flow but <br />sealed at low flow eventually filled with silt and sand and <br />became unusable as native fish habitat. Those with some <br />continuous flow provided good nurseries for native and <br />non-native fishes (Table V). Non-native fishes made up 72.0% <br />of the species composition in one breached backwater while <br />native species made up 28.0%. Redside shiner (Richardsonius <br />balteatus) and fathead minnow accounted for 68.8% of the <br />composition. The most abundant native species was [he <br />roundtail chub with 18.1% of the composition. Most roundtail <br />chub were Large yoy while most other species were small yoy, <br />suggesting that the native roundtail reproduces earlier, <br />grows faster and has a size advantage on sympatric species. <br />Colorado squawfish are not known to spawn at this location, <br />but if they did they would likely spawn later and the young <br />526 527 <br />
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