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<br />1 <br />A STUDY TO DETERMINE THE BIOLOGICAL FEASIBILITY OF PIT TAGS <br />FOR ENDANGERED FISHES IN THE UPPER COLORADO RIVER BASIN <br />INTRODUCTION <br />Tagging and marking are important techniques used to study individual aquatic <br />animals or populations, and are fundamental to effective fisheries management programs <br />I (Wydoski and Emery 1983). Various marking and tagging procedures have been used to <br />identify Colorado River endangered fishes as a part of numerous research and <br />management studies in the upper Colorado River basin (UCRB). These include <br />Carlin-dangler tags, anchor (Floy) tags, coded-nose-wire tags, and fin clipping with fin <br />mutilation using liquid nitrogen. None of these methods is without risk to the fish, and <br />therefore it is imperative to utilize tagging systems, methods of tagging, and associated <br />handling procedures which reduce adverse effects on these fish. <br />The Carlin-dangler tag has been used extensively on wild and hatchery-reared <br />Colorado River endangered fish over the past 10 years (Valdez et al. 1981; Miller et al. <br />1982; Archer et al. 1985). These species include the "endangered" Colorado squawfish <br />(Ptvchocheilus lucius), humpback chub Gila Mha), and bonytail Gila ele ans), as well <br />as the "candidate" razorback sucker (Xvruchen texanus). However, there are concerns <br />that this tag may be unsatisfactory because of its tag retention capabilities, and more <br />importantly, it may be injurious to the fish (e.g., punctures made by needles that are <br />used to attach the tag may cause secondary infections). In 1986, the former Upper <br />Colorado River Basin Biological Subcommittee recommended investigating a new tag, <br />