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ripe Colorado squawf ish at RK 250 (RM 156) in Three Fords Rapid. A total of 20 ripe or spent Colorado squawfish were captured in the FWS s tudy in the Xampa River at RK 29 (I3) and RK 27 (7). Included in the Yampa collections were 4 recaptu res, one originally tagged with a dangler tag in the Green River, and three tagged in the upper Yampa River. One of the Yampa recaptu res was a fish radiotagged in 1982 that did not migrate in 1982. Since that fish migrated and spawned in 1983, it is possible that the fish: (a) was not mature in 1982, (b) spawned in - alternate years, or (c) was physiologically stressed by surgery or handling and its spawning therefore inhibited. The recapture of a Colorado squawf ish tagged on the same spawning grounds in 1981 and one . tagged there in 1982 demonstrated a fidelity to the same grounds. Collections at both spawning sites produced 70 ripe Colorado squawfish from 1981-1983 (Table 2) . These fish were classified "ripe" if mi1_t or eggs could be expressed from the vent with light hand pressure on the abdomen. The average size of these fish was about the same in the Yampa and in Green rivers, with 44 Yampa males averaging 557 mm in length. Only 9 ripe or spent female Colorado squawfish have been positively identified by the expression of eggs. The average length of these females was 696 mm, which is significantly larger than the males taken with them. Since only 2 ripe females were taken in the Green River, no comparison was made between the Yampa and Green rivers with respect to the sizes of females. Table 2. Spawning Collections, Colorado squawf ish, Green and Yampa rivers. Number Male Female No. Year River Total Ripe n TL n TL Subadults 1983 Yampa 20 19 16 594 3 687 0 1983 Green 13 12 1.1. 568 1 625 1 1982 Green 13 7 6 509 1. 640 4 1981 Yampa ~ 34 31 27 535 4 734 1982 Yampa 1 1. 1 547 0 - 0 Physical measurements were made of various parameters at the spawning sites in 1983, but measurements of the Green River site were difficult to take because of the flood conditions. Cobble size located at the point of spawning for the Yampa River site was determined by measuring ,, volumetrically 10 cobbles taken at two sites in a M area selected from 58-cm depth water at locations where radiotelemetered fish appeared to be spaw~ing. The average size of the cobbles at these locations were 1560 cm and 1070 cm respectively. Other habitat data for spawning will be refined and presented in the 1984 project report. 13