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342 WADA AND KAEDING TABLE 1.-Total number of seine hauls, number of hauls with larval Colorado squawfish (in parentheses), and total number of larval Colorado squawfish collected in the upper Colorado River. Reaches are defined in Figure 1. No Colorado squawfish larvae were collected from reach 8. S = small larvae (6-10 mm total length); L = large larvae (11-21 mm). Year and month Reach 1 Seine Larvae hauls S L Reach 2 Seine Larvae hauls S L Reach 3 Seine Larvae hauls S L Reach 4 Seine Larvae hauls S L Reach 5 Seine Larvae hauls S L 1982 Jul 6(2) 0 3 0 0 0 0 Aug 2 (0) 1 (1) 0 1 11 (6) 13 40 14(6) 9 6 10(2) 12 6 1983 Jul 1(0) 0 0 9 (0) 0 0 5 (0) 0 0 2(0) 0 0 2(0) 0 0 Aug 4(0) 0 0 7(l) 1 0 17(l) 0 1 8(2) 1 2 8(0) 0 0 Sep 0 3(0) 0 0 5(2) 0 3 5(2) 0 3 3(0) 0 0 1984 Jul 6(2) 4 1 8 (0) 0 0 5 (0) 0 0 8(0) 0 0 5(0) 0 0 Aug 5(l) 0 1 14 (3) 16 8 7(3) 1 3 11 (1) 0 1 10(l) 1 1 Sep 1(0) 0 0 13(0) 0 0 5(0) 0 0 4(0) 0 0 2(0) 0 0 1985 Jul 0 10 (4) 3 16 12 (3) 3 1 12(2) 0 3 9(0) 0 0 Aug 0 9 (2) 1 9 13 (5) 1 14 12(5) 3 21 8(l) 0 8 Sep 0 12(l) 0 1 6(0) 0 0 4(0) 0 0 4(0) 0 0 cupied a small pool on 13 July. Sampling of the pool with trammel nets resulted in the capture of one radio-tagged fish and eight untagged adults, including five ripe males. Nine of the fish tagged in upper reach 6 and reach 7 moved downstream to a 16-km stretch of lower reach 6 during or shortly after the spawning period; four fish tagged in this vicinity moved up to reach 7. The movement between lower reach 6 and river reaches upstream appeared to follow a regular, seasonal pattern for some fish in the upper river. Unlike fish in reaches 6 and 7, those tagged in the other reaches showed no discernible move- ment pattern. Discussion Although radiotelemetry allowed us to locate the adult Colorado squawfish, it told us little about the behavior of the fish and nothing about their physiology. As a result, biological interpretation of our radiotelemetry data alone can be ambigu- ous. For example, the apparently seasonal nature of the movements of some radio-tagged Colorado squawfish between lower reach 6 and upper reach 6 and reach 7 seemed related to spawning. Our capture of one radio-tagged fish along with eight other adult Colorado squawfish (including ripe males) in reach 7 during July 1982 supported this interpretation. However, the rapid downstream displacement of some of these radio-tagged fish, which we observed soon after our sampling, might also have represented movement toward spawn- ing areas. Because our observations of recaptured Colorado squawfish during the spawning season indicate that milt can be expressed from individ- ual males over periods of at least 2 months, cap- ture of such fish cannot be taken as definitive ev- idence of nearby spawning grounds. Ova can be expressed from female fish only after ovulation, so the capture of fish with ova would be a better indication of nearby spawning activity; but we col- lected no individuals with expressible ova. Several attempts to recapture radio-tagged fish to check for both the occurrence of expressible gametes and the presence of untagged individuals failed be- cause the habitats could not be sampled effective- ly. The presence of larval Colorado squawfish may indicate that a spawning area is nearby, thus their capture could help to substantiate proposed spawning locations based on radiotelemetry data. Newly hatched Colorado squawfish are 5.5-7.0 mm long (Hamman 1981; Marsh 1985). Haynes et al. (1984) collected many Colorado squawfish larvae 8.8-17.8 mm long (11-25 d posthatching) in shoreline seine hauls like ours within 16 km of the important spawning site near RK 26.5 on the lower Yampa River described by Tyus (1985). We found Colorado squawfish larvae less than 11 mm long in every Colorado River reach except reach 7; larvae less than 22 mm were found in every reach. On the basis of the distribution of larvae and the locations of radio-tagged fish during the spawning season, we believe that Colorado i