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fish increased in length from 332 mm TL in 2004 to 352 mm TL in 2005 (20 mm change) and gained 68 grams (252 g in 2004 to 320 g in 2005) over the interval. One humpback chub we captured on 28 July 2004 at RK550.4 was a recapture (375 mm TL) that was first captured and tagged in Desolation Canyon at RK 338.9 on 14 April 2003. It moved upstream 212 RK and increased in length 114 mm over the recapture interval. That same recaptured 2004 individual was captured by electrofishing, the remainder of humpback chubs were captured in trammel nets. Humpback chubs ranged in length from 232 to 375-mm TL, the modal size class was 251 to 275 mm-TL (Fig. 17). The low number of humpback chubs collected over three years of study and the low proportion of humpback chub to roundtail chub (4/256) in samples collected in three consecutive sampling passes conducted in autumn 2003 in Whirlpool Canyon suggested that the humpback chub population in Whirlpool Canyon is relatively small at this time. This is supported by a companion study, where few humpback chubs were captured in the lower Yampa and in the Green River in Whirlpool and Split Mountain canyons (Finney 2006 draft). Extensive analysis of young chubs captured in Whirlpool Canyon and downstream did not reveal reproduction by humpback chub in the 2002 to 2004 period. The Black Rocks area of the Colorado River supports a substantial humpback chub population in a reach smaller than Whirlpool Canyon, so extent of habitat does not appear limiting. However, Black Rocks is much deeper and may contain more of the habitat preferred by humpback chub. Soundings conducted throughout Whirlpool Canyon near steep-walled areas revealed that few areas were deeper than 5 m, and most areas where humpback chubs were collected were 2 to 3 meters deep during summer low-flow periods. Deep pools with sufficiently low current velocity in which to set nets were also relatively uncommon in Whirlpool Canyon at flows > about 85 m'/s. Presence of all three chub species supports the idea that Whirlpool Canyon may be an important conservation area for chubs in the Green River Basin. Bonytail.-Our autumn 2004 Green River sampling occurred less than two weeks (22-23 Sept.) following two separate releases of hatchery-produced bonytail at the Echo Park boat ramp (RK 554.6, 12 Sept. 2004, n = 2,587, mean TL = 219 mm; 16 Sept. 2004, n = 2,988, mean TL = 55