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This study does not suggest one transmitter or battery type is better than another. Rather, I attributed most of the observed differences in tracking success to other, unknown factors that need to be evaluated. Although my use of a ratio of the field contact period to the theoretical radio life appears to be a crude way to evaluate radiotracking success, a comparison of the average performance obtained here (47.3X) with that of other investigators indicates it is accurate. I determined this by calculating performance ratios fcr all other radiotracking efforts on Colorado squawfish in the Green River Basin. Radant et al. (1983), using similar equipment in the White and Green Rivers (similar water conductivities), obtained an average performance ratio of 47.6X for t•e eight fish they studied. Wick et al. (1983), using different type radios ano receivers in the Yampa River (a smaller tributary with lower water conductivity), had a 49.6ro ratio for 12 fish. [Holden and Selby (1978) implanted five Colorado squawfish, but terminated their study due to equipment failure. I did not calculate a ratio for their work.] These results indicated that investigators using commercially available radios and tunable receivers can anticipate long-term success even in large, high conductivity rivers, if their radiotracking limitations are understood and enough radio tagged fish are used. I found that Colorado squawfish were easier than razorback suckers to radiotrack because they used shallow habitats most of the time. Razorback suckers were more difficult to track in spring and fall because they used deeper habitats. Radios with larger, more powerful batteries could not be used because the sucker is a smaller species (<_500 mm in length). Effects of implanted radios on fish growth were evaluated from a comparison of growth rates between recaptured implanted and recaptured non- implanted fish (Tyus 1988). Although lengths of all recaptured fish were not available, a comparison (Student's t) of the growth of 14 implanted Colorado squawfish (mean = 11.2 mm/year, SO = 10.2) indicated no difference in growth between these fish and 59 nonimplanted fish in the same size ranye (mean = 10.2 mm/year, SD = 11.3). Average growth rates of two razorback suckers (2.5 mm/year) from which implants were removed compared favorably with 39 nonimplanted fish (2.2 mm/year). This suggests that the implanted transmitters did not interfere significantly with feeding behavior and growth. The ratio of radio module weight to the body weight of Colorado squawfish averaged less than 1% (Table 2). This was also true for implanted razorback suckers. Long-term tracking by Mesing and Wicker (1986) and Miller and Menzel (1986) was also associated with a radio-to-fish weight ratio of less than 1.5%. This small ratio, and the use of beeswax as a coating for the radios, may have aided in the retention of radios implanted in this study; transmitter expulsion such as that reported by Marty and Summerfelt (1986) was not observed. EVALUATION OF BIAS IN COLLECTION DATA Habitat data recorded at the point of capture by electrofishing for 101 Colorado squawfish in 1980 and 1981 in the Green River (Tyus et al. 1984) were compared with habitat data (1281 observations) of radio telenetered fish. 148