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Last modified
7/14/2009 5:02:35 PM
Creation date
5/17/2009 10:51:31 PM
Metadata
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UCREFRP
UCREFRP Catalog Number
9410
Author
Wydoski, R. S. and E. J. Wick.
Title
Ecological Value of Floodplain Habitats to Razorback Suckers in the Upper Colorado River Basin.
USFW Year
1998.
USFW - Doc Type
Denver.
Copyright Material
NO
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<br />I <br /> <br />I <br /> <br />I. INTRODUCTION <br /> <br />I <br /> <br />Human alteration of the main rivers and tributaries in the Upper Colorado <br />River Basin (Upper Basin) had a major negative impact on some native fishes <br />to the point where the razorback sucker (Xvrauchen texanus), bony tail (Gila <br />eleqans), Colorado squawfish (Ptvchocheilus lucius), and humpback chub (Gila <br />cvoha) are now listed as endangered under the Endangered Species Act. Other <br />native fish species (e.g., flannelmouth sucker, Catostomus latipinnis and <br />bluehead sucker, Catostomus discobolus) are still able to maintain self- <br />sustaining populations, despite the drastic altered condition of the historic <br />river environment. In less altered river reaches, native fish species still <br />dominate the fish fauna (Anderson 1997; Burdick 1995) while, in more altered <br />reaches, nonnative fish species are more abundant demonstrating that they are <br />highly adaptive and can quickly dominate a fish community (Miller et al. 1982; <br />Tyus et al. 1982). <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />Many riverine fish species exhibit seasonal movements into inundated <br />floodplain habitats for spawning, rearing, and foraging (Copp 1989; Finger and <br />Stewart 1987; Lambou 1963; Ross and Baker 1983). Seasonal flooding is <br />important in sustaining various fish species that are characteristic of river <br />channels (Baker and Killgore 1994). Baker and Killgore emphasize that the <br />pattern of flooding appears to be of paramount importance in structuring <br />wetland fish communities and that fish may spread over large areas of the <br />floodplain during high streamflows. The lateral movement of fish on the <br />floodplain decreases exponentially with reductions in streamflow (Kwak 1988) <br />and recruitment may not occur if water levels remain low (Starrett 1951). <br />Dramatic declines of Age 0+ fish, that were correlated to the loss of <br />floodplain habitat, were reported by Coop (1990). A higher riverine fish <br />standing stock was associated with high spring floods in the Atchafalaya <br />floodplain in the lower Mississippi River whereas the standing stock was lower <br />following low spring floods (Bryan and Sabins 1979). Because of floodplain <br />importance to fisheries, the American Fisheries Society adopted a position to <br />"encourage restoration of historic floodplain and upland wetlands to regain <br />stormwater retention, conveyance, and low-flow augmentation capabilities of <br />the watershed, focusing on efforts to restore large 'functioning' floodplain <br />wetlands" (Rasmussen 1996) . <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />Habitat alteration and nonnative fish introductions were considered to be the <br />two most important factors in the extinction of 40 native North American <br />fishes (27 species and 13 subspecies) during the past century (Miller et al. <br />1989). These two factors also appear to be extremely important in the decline <br />of razorback sucker stocks in the Upper Basin and are undoubtedly related to <br />the decline of the other three endangered Colorado River fishes. <br /> <br />I <br /> <br />One of five major elements that are being addressed through the "Recovery <br />Implementation Program for Endangered Fish Species in the Upper Colorado River <br />Basin" (Recovery Program) is habitat development and maintenance (U.S. Fish <br />and Wildlife Service 1987). The declining numbers of some endemic Colorado <br />River fishes is attributed to the lack of recruitment. Although the long- <br />lived endangered fishes spawn successfully and produce larvae, high mortality <br />during the early life stages limits recruitment. Most Recovery Program <br />participants believe that the lack of recruitment in the razorback sucker is <br />related to the lack of adequate nursery habitat and predation/competition by <br />nonnative fishes. <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />This report summarizes the published literature on the ecological value of <br />floodplains to riverine fish communities and relates this literature to <br />reports on the ecological requirements of razorback suckers that have been <br />developed through the Recovery Program and management endeavors of biologists <br />in the Lower Colorado River Basin. It emphasizes the need for concurrent <br />integration of Recovery Program elements, particularly streamflow management, <br />habitat development and maintenance, management of nonnative fishes, and <br /> <br />I <br /> <br />I <br /> <br />7 <br /> <br />I <br />
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