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Executive Summary <br />The razorback sucker, Xyrauchen texanus, was listed as an endangered species in 1991 under the <br />Endangered Species Act of 1973, as amended. During the early 20th century the species was <br />abundant and distributed throughout the upper and lower Colorado River basin and its tributaries. <br />The decline of the species to the verge of extinction is attributed to the construction of massive <br />dams and water diversion projects that drastically changed the natural hydrology and aquatic <br />environments of the Colorado River. Competition with, and predation by, introduced nonnative <br />fish also add to the lack of recruitment by wild populations. <br />The Razorback Sucker Recovery Goals (U. S. Fish and Wildlife Service 2002) geographically <br />delineate the management efforts in the Colorado River basin as two recovery units: the upper <br />basin, including the Green River, upper Colorado River, and San Juan River subbasins; and the <br />lower basin, including the mainstem and its tributaries from Glen Canyon Dam downstream to the <br />international boundary with Mexico. The largest and most genetically diverse aggregation of <br />razorbacks resides in the lower Colorado River basin in Lake Mohave, Arizona. This aggregation is <br />considered to be the primary source for genetic material needed to recover the species in the lower <br />basin and perhaps throughout the entire Colorado River basin. The immediate conservation goals <br />for razorback sucker in the lower basin are to avert extirpation of the Lake Mohave population and <br />to conserve it as a genetic resource. Controlled propagation of the species at designated facilities <br />and reintroduction of fish into historic habitats are viable strategies and approaches to prevent <br />imminent loss and reestablish populations. Dexter National Fish Hatchery & Technology Center <br />(Dexter NFHTC) has contributed to the overall conservation effort since 1981. <br />This Genetic Management and Captive Propagation Plan (Plan) describes the guidelines used at the <br />Dexter NFHTC for developing and maintaining razorback broodstocks, experimental populations <br />and refugia maintenance. The Plan focuses primarily on genetic broodstock reserves and captive <br />iv