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1 r 1 r t I 1 1 years in the Juniper reach, and two of four years in the Maybell and Lily Park reaches. No significant correlations were observed between northern pike size and condition factor. Correlation coefficients between these two parameters were 0.00 for 1986-1988 and 1991, 0.38 for 1989, and 0.33 for 1990. Relative weight (Wr) was calculated for all northern pike length-weight data, using the standardized length-weight regression provided in Willis (1989) to normalize the distribution of the sample data and re-examine the transformed data set for significant differences in northern pike condition between years and river reaches (Appendix A, Table A-5). Average Wr for northern pike from 1988 to 1991 ranged from 106-117, indicating the Yampa River population was above average in condition for the species. The yearly pattern demonstrated a U-shape over the four years similar to average condition factors with the highest Wr indices occurring in 1988 and 1991, the higher flow years (Figure 10). Also similar were the large 95 % confidence intervals, indicating the range of values observed were not significantly different among years. Estimates of Wr were also calculated separately for spring and fall seasons in each year (Appendix A, Table A-5). Based on similarity of the average Wr values between seasons and large standard errors, northern pike condition did not vary significantly between seasons. Estimates of Wr for river reaches were similar with a low of 101 estimated for the Juniper reach and a high of 113 estimated for the Craig reach (Figure 10). Wr values for the Maybell and Lily Park reaches were both approximately 111. These values again show northern pike condition was average to above average in all four reaches, but not significantly different from each other based on 95 % confidence intervals. In contrast to length-weight regression slopes, condition factors, and Wr values indicating a general above average robustness in the northern pike population, the outward appearance of individual northern pike deteriorated noticeably in 1988-1989 during the pre-runoff and runoff periods in the Yampa River, when turbidity and debris load increased. Northern pike were observed with numerous lacerations and abrasions, particularly a large, rounded abrasion occurring at the tip of the lower jaw. Partial blindness, jaw wounds or broken jaw bones were also apparent. These injuries were attributed, in part, to decreased visibility for northern pike due to water quality conditions, which reduced their ability to avoid impacts with the substrate, rocks, and woody debris. One northern pike was captured by hand whose body appeared locked in a J-shape, causing the fish to move in a circular motion. Despite this apparent spinal injury or malformation, the northem pike did not appear emaciated and moved vigorously in a circular motion when disturbed. These physical problems were not noted, or did not appear prevalent enough to be noted in the 1990 and 1991 northern pike samples. Food habits fish prey composition and fish prey size Analysis of northern pike food habits was initiated in 1989, though four northern pike mortalities in 1988 were examined for stomach contents. Stomach contents for a total of 199 northern pike were recorded; 4 in 1988, 42 in 1989, 87 in 1990, and 66 in 1991. By river reach, stomach contents were examined for 50 in the Craig reach, 54 in the Juniper reach, 45 DRAFT March 12, 1996 32