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7/14/2009 5:01:47 PM
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UCREFRP
UCREFRP Catalog Number
8131
Author
Mueller, G., T. Burke and H. Horn.
Title
A Program to Maintain the Endangered Razorback Sucker in a Highly Modified Riverine Habitat.
USFW Year
1993.
USFW - Doc Type
W. O. Deason and S. S. Anderson, eds.
Copyright Material
YES
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IV*, <br />80 Environmental Enhancement of Water Projects <br />sole purpose of producing subadult suckers (Mueller and <br />Hertzog, 1992). <br />The on-site rearing program is a multifaced approach <br />integrating research and management objectives. The <br />goal is to assess the survival of 10,000 (minimum) <br />subadult razorback suckers released into the reservoir <br />from on-site rearing ponds. Supplemental feeding, <br />fertilization, pen culturing, hatchery production, or <br />combination of these alternatives would be adopted if <br />the concept fails to provide adequate numbers of <br />suckers for stocking. <br />Results are being analyzed annually. At the end of a <br />year program, a determination will be made regarding <br />population augmentation, survival rates of stocked <br />fish, status of the existing population, and cost <br />analyses comparison of other alternatives. If the <br />effort proves successful, the report will also make <br />recommendations on future stocking rates, needs for <br />additional backwater facilities, research, and <br />management objectives. <br />This approach is unique in that most endangered species <br />programs aim for total recovery. For example, The <br />Recovery Program for the Endangered Fishes of the Upper <br />Colorado is attempting to repair man's impact to more <br />pristine areas of the upper basin. The program is <br />intended to enhance razorback sucker and other native <br />fish populations through habitat restoration. <br />Unfortunately, habitat restoration is not feasible in <br />the lower basin due to the magnitude of habitat <br />alteration. Even if dams were removed, reservoirs <br />drained we would still be unable to remove the exotic <br />game fish which prey upon their young. However, we can <br />maintain and possibly enhance the existing population <br />through an active management program. <br />The NFWG recognizes that agencies must pool their <br />resources to salvage this population. Unless steps are <br />taken to assist these fish, this population will <br />disappear as have other older reservoir populations. <br />RESULTS TO DATE <br />Two backwaters were isolated from the reservoir for <br />spawning and rearing purposes. Permanent and temporary <br />barriers are being tested as a means of creating <br />refugia. Permanent or earthen barriers provide <br />additional benefits; however, they are more expensive <br />Razorback Sucker Program 81 <br />and sometimes are impractical because of poor equipment <br />access or highly fluctuating reservoir elevations. <br />Temporary barriers constructed of netting are usually <br />more economical and easier to install. They also can <br />be installed and later removed without scarring the <br />landscape. <br />Yuma Cove. The existing natural berm at Yuma Cove <br />isolated a 2 acre (0.8 hectare) portion of the <br />backwater during low reservoir elevations. This berm <br />was enlarged and elevated above maximum reservoir <br />elevations using large earth moving equipment. After <br />years, the barrier's integrity has not been <br />compromised, although storm induced wave action has <br />eroded portions of the levee. <br />Yuma Cove was poisoned in the fall of 1990 to remove <br />all exotic fish. One-hundred (67 male, 33 female) <br />adult razorback suckers were stocked into the cove just <br />prior to spawning season in 1991 and 1992. In both <br />years, new spawners were collected from the reservoir, <br />allowed to spawn, then recollected and returned to the <br />reservoir. Spawning was successful in both years and <br />larval suckers were collected. <br />Larval light traps were developed to help detect the <br />presence of sucker larvae and help monitor spawning <br />success. Light traps not only attracted large numbers <br />of sucker larvae, but also aquatic insects. We <br />discovered that by only having suckers in the <br />backwater, the numbers of odonate nymphs (damsel and <br />dragon fly) exploded. Light traps set overnight <br />commonly captured up to 5,000 large odonates per set <br />(Mueller et al., IN PRESS 1993). Aquarium tests <br />placing odonates and larval suckers together showed <br />that, under those conditions, the odonates were <br />effective in capturing and eating larval suckers (Horn <br />et al., in press). <br />No juvenile suckers were produced in 1991. Losses <br />could not be attributed to odonate predation or any <br />other known reason. However, 296 juveniles, averaging <br />lengths of 14 inches (35 cm), were collected in <br />November, 1992. Roughly half of the suckers were <br />tagged and released into the main reservoir. The <br />remaining half were transported and released in Davis <br />Cove. <br />Aquatic weeds were a major problem during the summer of <br />1992. Sago pondweed infested the shallow backwater and <br />complicated efforts to recapture spawners or their <br />young. Pondweed had to be manually removed to allow
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