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29 <br />The daily plots of these fish show them remaining in the vicinity of <br />their original capture (Fig. 3). Close contact throughout the spawning <br />period in the Upper Yampa River was not made with all these fish because <br />of intense tracking efforts inside Yampa Canyon. We assumed that these <br />fish, which had operational tags through mid-August did not migrate into <br />Yampa Canyon, since no contact was made within Yampa Canyon during the <br />spawning period. The sizes of the nonmigratory fish were 554 mm (#8), <br />565 mm (#6), and 566 mm (#2) TL. Miller et al. (1983b) reported that <br />the average size of four nonmigrants tagged on the Green and White <br />rivers was 476.5 mm TL and that average size of 11 migrants from the <br />Yampa, White, and Green rivers was 565 mm. Seethaler (1978) reported <br />100° sexual maturity in 11 female and 48 male Colorado squawfish over <br />503 mm TL. Hamman (1981) reported that hatchery reared Colorado squawfish <br />became mature at age V for males 317-376 mm TL and age VI for females <br />425-441 mm TL. The mean total length of nonmigrants in 1982 was 562 mm'. <br />According to reports cited above, these fish were probably sexually <br />mature. However, because of either small numbers of fish examined, <br />different conditions under which fish were reared, and different rivers <br />in which squawfish were tagged in the above studies, no firm conclusions <br />can be drawn regarding sexual maturity of Yampa River nonmigrants in <br />1982. <br />Another explanation of why these fish did not migrate is that they <br />spawned "in place." However, larval and young-of-the-year (YOY) Colorado <br />squawfish have not been collected above Harding Hole, river km 34, <br />indicating that successful reproduction does not take place above Yampa <br />Canyon. Another possibility is that all Colorado squawfish do not spawn <br />every year. This could be because they spawned the previous year and