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I~ L1 1 Average length of the 1988 year class in fall 1988 was 38 mm TL and average length in spring 1989 was 42 mm TL. Average overwinter growth was 4 mm TL. Sixty juveniles were captured in fall 1988, 10 were captured the following spring. These fish ranged from 61 to 99 mm TL in fall and from 72 to 101 mm TL in spring. These juveniles were considered to be from the 1987 year class. Distributions of age-0 Colorado squawfish captured in fall 1988 and spring 1989 are presented in Figure A-9. As in 1987, the majority (83%) of age-0 captured in Fall 1988 were above RM 25. However, during spring 1989 the distribution shifted and a larger proportion of age-0 (54%) were captured in backwaters below RM 25, indicating downstream movement by age-0 Colorado squawfish during winter months. 3.1.3 1989 Year Class Sampling in fall 1989 and spring 1990 on the Green River was extended upriver from Mineral Bottom (RM 52) to Green River, UT (RM 119.8). A total of 1527 age-0 Colorado squawfish were captured in Reach 3 in fall 1989 for a CPE of 19.9/100 m2. By the following spring 1990, total numbers decreased by 46% to 821, and CPE decreased significantly (Student's 't', P>0.05) by 56% to 8.82/100 m2. Average length of the 1989 year class in fall 1989 was 37 mm TL and average length in spring 1990 was 41 mm TL. Average overwinter growth was 4 nun TL. The number of juveniles captured in fall 1989 and spring 1990 was S8 and 68, respectively. These fish ranged from 70 to 131 mm TL in fall and from 75 to 162 mm TL in spring. This unusually high number of juvenile squawfish were thought to be from the strong 1988 year class. Expansion of the study reach allowed for a more comprehensive view of possible shifts in distribution between fall 1989 and spring 1990. Although results were inconclusive, the data suggested a possibility of downstream shift in distribution of fish from fall to spring. Of twelve S-mile sections in the upper 60 miles of the study area, all showed higher CPE's in fall. Conversely, of twelve sections in the lower half, four (RM 15-20, 25-30, 30-35 and 45-50) had higher CPE's in spring (Figure A-10). 3.1.4 1990 Year Class A total of 418 age-0 Colorado squawfish were captured in this reach in fall 1990, resulting in a CPE of 2.46/100 m=. By spring 1991, total numbers decreased to 212 and CPE was 2.29/100 mZ. CPE decreased by 7%, (not significant, Student's 't', P>0.05) total numbers decreased by 49% from fall 1990 to spring 1991. Fish captured in spring 1991 averaged 49 mm TL, compared to those captured the previous fall 1990 which averaged 40 mm TL. This resulted in an average growth of 9 mm from October to March. ' A total of 21 juvenile Colorado squawfish, ranging from 61 to 88 mm TL were captured in fall 1989. This compared to 42 juveniles, ranging from 70 to 103 mm TL captured in spring 1991. ' Distribution of age-0 Colorado squawfish captured in fall 1990 and spring 1991 are presented in Figure A-11. CPE was highest between Bull Hollow (RM 84.5) and Horseshoe Canyon (RM 60) during fall 1990, but by spring 1991 higher densities of age-0 squawfish were- found between Horseshoe Canyon (RM 61) and Bonita Bend (RM 31), 20-30 miles downstream.