7277 - Laserfiche WebLink

Home Browse Search

? GENERAL IlnRODUCTIm The razorback sucker, X auchen texarnas (Abbott), a native of the Colorado River system of western North America, once ranged from W arcing to the Gulf of California. Development of the Colorado River and its major tributaries for water and power have greatly impacted and reduced razorback sucker populations. Minckley (1983) t oroughly reviewed the historical distribution of this species and documented its demise in the lower Colorado River basin. He suggested that localized extirpations followed a pattern whereby only large individuals can be found in the reservoirs in the years following impatuxhnent. while larval razorbacks may be collected, juveniles are almost never found. After a time, these populations of large, old fish dwindle and disappear (as did those in the Salt River reservoirs, Roosevelt and Saguaro lakes), or became severely reduced (as in Lakes Mead and Havasu on the mainstem Colorado River) (Minddey 1973, 1983). In Lake Mohave, Arizona Nevada, the last reservoir constructed on the lower Colorado River mainstem, remains the only sizable population of adult razorback sucker (Minckley 1983). It is estimated from aging data that these fish hatched in the early 1950s, about the time the reservoir was filling (McCarthy and MinckleY 1987). Each January through March, razorback suckers may be observed moving' onto gravelly shoals to spawn (Minckley 1973). Larvae can be captured in February through Apri.l? but, curiously, none larger than about 12.0 mm TL has ever been taken _, (Marsh and Lwighorst 1988).