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.-. <br />w <br />a. <br />U~ <br />C ~ <br />d L <br />~3 <br />U ~ <br />7 <br />+`- tT <br />m ~ <br />O <br />O~ <br />N t3 <br />~ O <br />O <br />U <br />1b <br />1.2 <br />.8 <br />.4 <br />0 <br />1.6 <br />1.2 <br />.8 <br />.4 <br />0 <br />1.6 <br />1.2 <br />.8 <br />.4 <br />0 <br />1.6 <br />1.2 <br />.8 <br />.4 <br />0 <br />10-Mile Subreach 10-Mile Subreach <br />Figure 3.-Distribution, by 10-mile Subreach, of YOY Colorado squawfish in the Colorado and <br />Green Rivers, fall 1994. <br />Size Distribution <br />Mean size of YOY Colorado squawfish was higher in 1994 than recorded previously in ISMP <br />(Figures 4, 5; Tables A-3, A-4). Mean length was 64 mm in Reach 1, 52 mm in Reach 3, and 67 <br />mm in Reach 4. Fish as long as 90 to 110 mm were considered YOY in reaches 1 and 3 because <br />there was no clear break in the length-frequency distribution. Also, investigators who had been <br />sampling through the previous summer had observed earlier spawning and faster growth than had <br />been seen in previous years (UDWR, unpublished data). However, Valdez et al. (1995) aged several <br />fish in this size class as Age II in spring of 1995, suggesting some of the fish reported here as YOY <br />could have already been 1 year old when captured in fall of 1994. Regardless of the age of the <br />largest fish, mean size of YOY Colorado squawfish was considerably larger than in previous years. <br />The larger size of the fish could be at least partially responsible for the decreased catch rates. One <br />explanation could be that the large size of many YOY Colorado squawfish allowed them to move out <br />of the backwaters earlier than in previous years and they were unavailable to fall backwater seining. <br />Sympatric Species <br />The percentage of native fishes in the first seine haul in primary backwaters declined in 1994 <br />(Figure 6; Table A-5). The decrease was greater in reaches 2 and 3, where the percentage of native <br />fishes went from 13 9b to 0.190 and from 25 % to 1.4% (respectively). <br />5 <br />a1 10.1 2a1 30.1 40.1 60.1 60.1 70.1 60.1 90.1 100., <br />-a -2o ao -~o so -6o ao ~o -90 -100 -1w <br />0.1 10.1 20.1 30,140.1 bo.160.170.1 60.190.1 100.1110.1 <br />-w -2o ao .40 -so ~o ao -eo -90 -100 -110 -t20 <br />uo- 1so- 160- <br />149.9 159.9 169.9 <br />210.1220.1 230.1 240.1250.1260.1270.1 280.1 290.1 300.1 310.1 <br />-220 -230 -240 -250 -260 -270 -280 -290 .700 310 J20 <br />