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19 fluctuations in the backwaters resulted in a lower mean temperature than that of the main channel. If Colorado squawfish follow temperature gradients closely, this would result in much greater movement in and out of backwaters on a daily basis than previously surmised. Temperature related to growth Thompson (1991) reported that YOY squawfish cease growth at 13° C. Main channel and backwater temperatures were greater than 13 from mid-March to mid-October. Since YOY squawfish are first present in the river near the end of June, their fall growing season is about 3.5 to 4 months long. High peak flow was directly correlated to later hatch dates and lower degree day accumulation (Trammell and Chart 1998; larval drift), and thereby to smaller total length of CS in the fall (Figure 2). In low water years the fish spawned earlier, thereby lengthening the growing season, and resulting in larger fish in the fall. Low water also allowed the river to warm up faster and for backwaters to reach a higher maximum temperature. Degree day accumulation was calculated from first hatch date to fall sample date, and regressed against fall TL, resulting in an rz of .65. When 1992 was removed from the regression, rz became .91. The total length of squawfish in the fall was related to overwinter survival and continued overwinter growth. The smaller the fish in the fall, the greater the decline in catch rates from fall to spring (Figure 3), which suggests some size-related overwinter mortality. However, all years except `95 showed some growth occurring between the fall sampling and the spring sampling. Maximum, minimum and average TL, all increased over winter (Table 9). Fall and spring sampling dates bracketed the dates the river fell below and rose above 13° C, with a few days above 13° C on either end.