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20 sample size from influencing parameter estimates. Pooled weight-length regression equations by river are: White River Loglo W :: -6.384 + 3.463 * LoglO L, LoglO W = -5.692 + 3.206 * LoglO L, Loglo W :: -5.555 + 3.156 * LoglO L, Loglo W = -6.026 + 3.339 * LoglO L, Colorado River Green River Yampa River where W is weight in grams and L is TL in mm. Regressions for fish from the Colorado and Yampa rivers were very similar, as were the regressions for fish from the White and Green rivers. These relationships were best shown by estimating weight from a series of lengths using each regression equation (Figure 10). They demonstrate that Coloradosquawfish collected from the Colorado or Yampa rivers tend to become heavier with length than fish collected from the Green or White rivers. Vanicek and Kramer 1969) reported a weight-length relationship for fish from the Green River.: LoglO W :: -5.41S + 3.126 * LoglO L. Seethaler (1978) reported weight-length relationships for fish from the Colorado, Green, and Yampa rivers: Green and Yampa rivers LogJ(j'W:: -5.54 + 3.16 * LoglO L, LoglO W = -5.38 + 3.12 * LoglO L, Colorado River Green, Colorado, and Yampa combined LoglO W :: -5.38 + 3.11 * LoglO L. Seethaler (1978) suggested that length-weight relationships for fish from the Green and Colorado rivers were not significantly different, supporting his hypothesis of a single genetic population. Although Vanicek and Kramer (1969) reported collecting 1469 Colorado squawfish from May 1964 to October 1966, they do not report the number of fish used in their regression analysis or when they were collected. Seethaler (1978) suggested that Vanicek and Kramer (1969) based the relationship on 182 fish used in their scale analysis of age. Thus. their data were not directly comparable with data in my analysis. Pooled estimates are more accurate and unbiased by months with larger numbers of captured fish. In addition, segregation of immature and mature sexual stages should increase precision because immature fish would not gain weight at the same rate as mature fish during the spawning period. Pooled weight-length regressions reported here can be used to compare a fish to the average or expected weight of fish from the same river. To account for influence of season, coefficients for each month can be used in the comparison. These equations should be useful in assessing the "health" of captured fish and may influence decisions on whether or not to implant a fish with a radio-transmitter. Comparisons might also be made of relative condition of fish collected from different habitats. Mean Kn values were calculated monthly for mature fish from each river (Figure 11). Although Kn was not comparable between rivers, comparisons can be made between months. For fish from the Colorado, Green, and Yampa rivers. maximum condition occurred in June prior to spawning. Minimum condition occurred in July or August, probably as a result of migration or spawning. Fish from each river recovered in late summer or early fall, suggesting the importance of feeding and growth during this period.