Laserfiche WebLink
<br />. <br /> <br />INTRODUCTION <br /> <br />. <br /> <br />The n~tive fishes of the Colorado River basin comprise one of the <br />most unique fish faunas in North Anerica. Miller (1959) calculated 74 <br />percent endemism for species of native Colorado River basin fiShes" one <br />of the highest found in North _rica. Reasons for this are integrally <br />tied with the geologic history of the basin" primarily a long period of <br />isolation. The Colorado River is unique" beginning as a cold" clear <br />stream in the Rocky Mountains and then plunging into a dry desert where <br />it has cut spectacular canyons. Here it is a warm" turbid" often vio- <br />lent river, given to sudden and drastic changes in volume and turbidity. <br />Thei canyons and rapids of the Colorado River system are well known for <br />their scenic beauty and river rafting qualities. Not so well known is <br />the fish fauna that evolved with the river as it cut its present course. <br />The endemic Colorado River basin fishes can be divided into two <br />categories: small stream forms found primarily in the lower basin and <br />large river forms found in the main stream and larger tributaries. To- <br />day much of the Colorado system is composed of large reservoirs with <br />cold" clear tailwaters" very different than the natural. warm" turbid <br />river. '!his has had a pronounced effect on the native fish fauna <br />where drastic reductions in distribution are common. Miller (1961) and <br />Mincldey and Deacon (1968) documented the decrease in native fishes in <br />the lower basin. Many of the small stream endemics are either extinct <br />or present in limited areas" often one spring. Miller and Pister (1971) <br />discuss some of the W)rk presently being done to protect remaining <br />species. The large river fishes are" for the most part" extremely rare <br /> <br />'. <br />