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<br />. <br /> <br />. <br /> <br />. <br /> <br />.MAY-15-1998 15:49 <br /> <br />BOR LULND <br /> <br />9706633212 P.10/24 <br /> <br />9 <br /> <br />occupied by two fish equipped with transmitters yielded an additional male <br />Colorado squawfish in spawning condition. During this same time period, an <br />adult female was captured near river mile 175 that weighed nearly 1 pound more <br />than when previously captured a month earlier, suggesting the development of <br />spawning (gravid) condition. <br /> <br />larval Occurrence <br /> <br />Fishery Project studies included the routine sampling of the larval-fish <br />community, both within and downstream of the IS-mile reach. During 5 years <br />of investigation, 70 larval squawfish were collected with fine-mesh hand <br />nets from the two Colorado River reaches in the Grand Valley immediately <br />upstream and downstream of its confluence with the Gunnison River. Although <br />the sampling effort was similar in the two river reaches, 96 percent of the <br />larval captures occurred downstream of the Gunnison River confluence (river <br />miles 162-164). Only two (3 percent) of the larvae were collected from the <br />upstream reach. These observations may indicate that most fish were spawned <br />in the downstream reach or that the larvae were deposited in the upstream <br />reach and drifted downstream to the area where most of the captures were <br />recorded. <br /> <br />Postlarval Youna-of-Year Occurrence <br /> <br />No postlarval young-of-year Colorado squawfish greater than 25 mm total length <br />were collected from above the Gunnison River confluence in a total of <br />57 samples collected in the fall of 1982-1986. However, a total of <br />62 Colorado squawfish were collected in an 18-mile reach below the confluence <br />of the Gunnison River (54 samples). The 1982-1984 catch rate of young-of-year <br />Colorado squawfish in the 10-mile reach immediately downstream of the <br />confluence of the Gunnison River (riyer miles 160-170) warranted <br />classification of this reach as a 'Voung-of-Vear Nursery Area" by the Basin <br />Biology Subcommittee (U.S. Fish and Wildlife Service 1984). <br /> <br />NonsDawnino Adult Occurrence <br /> <br />Osmundson and Kaeding (1989) reported that adult Colorado squawfish catch <br />rates in the upstream IS-mile reach were twice as high as those in the <br />adjacent downstream river reach. During 1986-1989 adults were most abundant <br />in a 1.3-mile segment (river miles 174.4-175.7) of the IS-mile reach during <br />high water, particularly in two gravel-pit ponds that were accessible during <br />high flows. These fish may have moved into these ponds to feed and rest, or <br />they may have been attracted to the warm, productive environments that the <br />ponds provided (pond temperatures were as much as 10.5 .C warmer than the <br />adjacent river). Some of the squawfish captured from one pond were well <br />tuberculated by June 3, when nearby river temperatures were only 10 .C-13 'C <br />(Kaeding, pers. comm.). It has been hypothesized by some' investigators that <br />thermal energy units aboye those provided in the mainstream are important to <br />gonadal maturation. If this ,is true, then access to these sheltered off- <br />channel pools may be very important to successful spawning in the upper <br />reaches of the Colorado River. Historically, bottomlands that routinely <br />flooded during the spring runoff period would haye provided these warm <br />