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Last modified
7/14/2009 5:02:32 PM
Creation date
6/1/2009 11:28:31 AM
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UCREFRP
UCREFRP Catalog Number
8002
Author
Bozek, M. A., L. J. Paulson and J. E. Deacon.
Title
Factors Affecting Reproductive Success of Bontytail Chubs and Razorback Suckers in Lake Mohave.
USFW Year
1984.
USFW - Doc Type
Technical Report No. 12,
Copyright Material
NO
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<br />observed or collected in recent years. <br />The apparent lack of young individuals in the bonytail chub and <br />razorback sucker populations suggests that recruitment is limited <br />(Gustafson 1975a,b; Minckley 1973; Minckley 1983). Jonez and Sumner <br />(1954) noted that predators were numerous in the vicinity of razorback <br />sucker and bonytail chub spawning areas. Predation on early life stages <br />of both species is believed to be the principal factor limiting <br />recruitment in these reservoir populations (Minckley 1973; Minckley <br />1983). <br />The U. S. Fish and Wildlife Service initiated this investigation in <br />order to further evaluate the population status and reproductive success <br />of razorback suckers and bonytail chubs in Lake Mohave. The principal <br />objectives were to determine (i) the distributions and abundances of <br />both species, (ii) whether successful spawning occurs for either <br />species, and (iii) the primary factors affecting spawning success. <br />1.2 History of the Lake Mohave Area <br />The construction of Hoover Dam in 1935 stabilized flows and <br />drastically reduced, suspended sediment loads in the Colorado River below <br />tfie dam (Dill 1944). The river was transformed from a seasonally warm, <br />silt laden, turbulent stream to a cold, crystal-clear regulated river <br />(Jonez and Sumner 1954). The swift currents degraded the river bottom <br />and exposed large, stable substrates to 70 km below the dam by 1947 <br />(Jonez and Sumner 1954). This allowed for the extensive colonization of <br />Cladophora sp. in shoal and riffle areas (Moffett 1942). Mayflies <br />(Callibaetis sp.) were abundant in the river while midge larvae, <br />caddisflies, dragonflies,,damselflies, and microcrustaceans (Daphnia sp.
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