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fish habitat based on general river geomorphology (Tyus et al. 1984). Habitats within these stations were sampled using electrofishing, trammel nets, seines, and wire traps, depending on the suitability of each gear type, but only electrofishing data were used for comparisons. The habitat and substrate types at the point of capture for each Colorado squawfish were recorded, and water depth and velocity were measured as previously described. Growth rates of implanted Colorado squawfish and razorback suckers from which radios were removed were compared to nonimplanted fish of the same size, by obtaining fish lengths from capture-recapture records. Only fish recaptured from the Green River Basin whose lengths fell within the size range of the implanted fish were used for this comparison. RESULTS AND DISCUSSION Radiotracking Evaluation A total of 92 Colorado squawfish were captured and implanted with one of the four radio modules evaluated during the study period. There was no significant difference (Student's t, P < 0.01) in the average battery life obtained by tracking mercury and lithium modules under fielc conditions (47% and 47.5% of theoretical) but there was a wide range between the four radio types: from 34% to 60%. Radios were small with respect to the sizes of the fish used; they were less than 1% of the average fish body weight and about 10% of the average fish length (Table 2). Table 2. Type, longevity (duration of field contact), and size of radios implanted in Colorado squawfish and tracked in the Green River 1980-1985. n = sample size. Type A and B = Smith-Root modules, Type C and D = AVM modules. Average Rated Longevity observed/ Transmitter size Average life Average Range rated % fish % fish fish Type n (d) (d) (d) life (%) weight length TL (mm) A 25 150 90 57-167 60 0.5 7.3 687 B 9 300 102 71-167 34 0.9 12.1 6E~ C 43 180 86 0-157 48 0.8 9.0 557 D 1S 550a 260 93-543 47 1.1 14.0 642 AVERAGE 41.3 0.8 9.7 625 aListed as 1~ year by manufacturer. 146