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15 Colorado Squawfish A total of 105 Colorado squawfish YOY were collected by seine and dip net in the Colorado River during 1979-1983 (Table 4). Numbers per year ranged from 77 in 1980 to 1 in 1981. All specimens were collected in low velocity habitats (e.g., shallow shorelines, backwaters, concavities, and isolated pools) between river km 212.2 and 245.7. Specimens were collected as early as 27 July in 1981 and 1982 and as late as 2 November in 1980. C/f ranged from 0.05 in 1981 (one individual) to 0.31 in 1982 (16 individuals). Size (mm TL) at time of capture ranged from 7.8 (27 July 1982) to 38.0 (2 November 1980). Colorado squawfish spawning was estimated to have occurred as early as 3 July in 1981 and as late as 6 September in 1980. Two age I Colorado squawfish were collected by seine in 1983. One (TL=65.0 mm) was sampled at r~ver km 218.1 on 2 August in a tributary stream embayment, and the second (TL=76.2 mm) was collected at river km 224.6 on 19 September in a mainchannel backwater. Predictive age equations did not permit estimates for individuals of this size. Two larval Colorado squawfish (TL=9.0 and 9.5 mm) were collected by drift-net on 27 July 1982 (Table 3). These specimens were estimated to be 11.4 and 13.2 days old, respectively, meaning they were spawned on 15 and 17 July. The relationship between flow/water temperature and estimated Colorado squawfish spawning dates for the months April-September 1979-1983 is presented in Figure 3 and Table 5. In general, estimated spawning dates coincided with decreasing flow and rising water temperature. In 1979, spawning was estimated to have occurred from 16 July to 4 August when maximum fJow at the Colorado-Utah state line decreased from approximately 297 to 125 m per second (m3/sec). Maximum mainchannel water temperature during that period was always greater than 20 C; however, minimum water temperature was occasionally lower. Mainchannel water temperature 22 C occurred by 22 July and lasted well into August. Spawning in 1980 was estimated to have occurred from 16 July to 6 September. Maximum flow during that period ranged from approximately 178 to 115 m31sec and maximum mainchannel water temperature was always greater than 22 C. During the very low flow year of 1981, when peak flow reached only 184.5 m3/sec, only one YOY Colorado squawfish was collected, suggesting a brief spawning period. In 1983, the estimated spawning period was 15 July-ll August. Maximum flow during that period ranged from 218 to 135 m3 and maximum mainchannel water temperature ranged from 21.0 to 23.5 C. Flow in 1983 was high, with a peak discharge of 1,705 m3/sec on 27 June. Estimated spawning period for 1983 was 27 July-10 August. Maximum flow during that period ranged from 515 to 334 m3/sec and maximum mainchannel water temperature ranged from 19.0 to 23.0 C.