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<br />enclosures will be established in Millard Canyon and six in selected habitats of the Bonita
<br />Bend-Anderson Bottom reach. The experiment will be conducted over a temporal scale with
<br />sucker larvae collected in light traps from the nursery habitats at three different phases of
<br />development (Le., pre-flexion mesolarva, post-flexion mesolarva, and metalarva); each
<br />developmental phase will be considered a separate test. For each test, 50 sucker larvae of
<br />known size (TL) will be placed in each enclosure. Three enclosures at each site per test will
<br />also be stocked with 10 adult red shiner. Duration of each test will be 7 d. Food resources and
<br />various physical parameters inside and outside each enclosure will be monitored daily during
<br />each test. Survival and growth of sucker larvae in each enclosure will be recorded at the end of
<br />each test.
<br />
<br />RESULTS AND DISCUSSION
<br />
<br />Fish Collections: 1993, 1994 (Objectives 1-4), and 1995 (Objective 1)
<br />
<br />1993, lower Green River, Millard Canyon and Anderson Bottom-Bonita Bend,
<br />17-19 June.-A total of 523 fish was collected in 30 light trap (509) and two seine samples
<br />(14). Nonnative minnows dominated the catch (76% of total number collected), with red shiner
<br />(43%, GMcpe for light trap samples = 4.8), fathead minnow (6%,0.6), and unidentified nonnative
<br />minnows (24%, 1.5) predominating (Table 1). Common carp Cyprinus carpio was the other
<br />nonnative collected. Native fishes collected included Colorado squawfish, speckled dace
<br />Rhinichthys oscu/us, f1annelmouth sucker, and razorback sucker. A total of 122 (23%,2.4)
<br />razorback sucker larvae was collected (120 with light traps and two with seines), ranging in size
<br />from 11.0 to 16.0 mm TL (Table 3); 117 were collected inside Millard Canyon and five were
<br />collected in a flooded wash at Anderson Bottom. One juvenile Colorado squawfish (> 41 mm
<br />TL) was collected by seining inside Millard Canyon.
<br />
<br />1993, Colorado River inflow to Lake Powell, 20-23 June and 3-6 August.-A total
<br />of 17,265 fish was collected in 20 light trap (16,448) and eight seine samples (817) during
<br />20-22 June, and 29,071 in 33 light trap samples during 3-6 August (Table 2). Nonnative
<br />minnows dominated the catch in each sampling period (> 99% of total number collected during
<br />each sampling period), with red shiner (15%, GMcpe for light trap samples = 43.0 during June;
<br />11%,29.0 during August), common carp (21%,105.2), sand shiner (12%,6.7; 1%, 1.7),
<br />fathead minnow (12%, 45.8; < 1%, 0.7), and unidentified nonnative minnows (41%, 167.2; 87%,
<br />47.1) predominating. White sucker Catostomus commersoni, black bullhead Ameiurus me/as,
<br />channel catfish, green sunfish Lepomis cyane/lus, and black crappie Pomoxis nigromacu/atus
<br />were the other nonnatives collected. Native fishes collected included Gila sp., Colorado
<br />squawfish, speckled dace, bluehead sucker Catostomus discobo/us, flannelmouth sucker, and
<br />razorback sucker. A total of 15 razorback sucker larvae was collected with light traps from
<br />Sheep Canyon during June sampling (GMcpe = 0.4), ranging in size from 13.0 to 16.0 mm TL
<br />(Table 3). Six juvenile Colorado squawfish (55-83 mm TL) were collected with seines from
<br />sidechannel habitats during June sampling, and 12 larval Colorado squawfish (10.0-12.0 mm
<br />TL; GMcpe = 0.3) were collected with light traps during August sampling (eight inside Sheep
<br />Canyon, two inside Dark Canyon, and two inside Gypsum Canyon). No Colorado squawfish o.r
<br />razorback sucker larvae were captured in the Colorado River inflow to Lake Powell during
<br />sampling in 1994 and 1995. Perhaps the flowing, lotic conditions that were present in 1993 but
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