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<br />Total length data were examined to determine the relative abundance of
<br />young-of-the-year (YOY), juvenile, and adult fish per species for 1991-1993.
<br />Age class breakdowns were taken from data sheets used by the Service's CRFP
<br />office in research done on the Colorado and Gunnison Rivers. Mean total
<br />length was used to determine population size-structure trends for the four
<br />most common species (flannelmouth sucker, bluehead sucker, channel catfish,
<br />and common carp) by reach, by trip, and by year, and for all species captured
<br />in a year (e.g. - Table 14, p. 44), for the first three years of sampling.
<br />Tracking data were examined to determine: 1) total number of river miles
<br />fish moved, from the most upstream contact to the most downstream contact
<br />(total longitudinal movement); 2) maximum distance and direction moved from
<br />point of release (maximum displacement); 3) distance and direction from point
<br />of release to point of last contact (final displacement); and 4) habitat types
<br />utilized (this data was combined with 1991 and 1992 data to obtain cumulative
<br />totals).
<br />
<br />RESULTS AND DISCUSSION
<br />
<br />A total of 175.8 miles were electrofished in July and October 1993 with a
<br />total effort of 453.4 hours. Six trammel net sets were recorded in 1993.
<br />Sampling occurred in May and October as in 1991 and 1992, however the
<br />variation in stream flow was fairly large between years (Table 1, Tables 12
<br />and 13 in Appendix II). Unless otherwise stated, the following data represent
<br />only standardized sampling trips (July and October).
<br />
<br />Distribution and Abundance
<br />
<br />A total of 21,961 fish representing five orders, six families, sixteen
<br />species, and one hybrid was collected in 1993 (Table 2). Table 2 also
<br />denotes the six-letter codes used to represent these species in all graphs,
<br />tables, and charts in this report. Eight species accounted for 99.6% of the
<br />total catch (Table 3, Figure 4). Three of these species were native
<br />(flannelmouth sucker, bluehead sucker, and speckled dace), one was a hybrid
<br />(flannelmouth sucker X bluehead sucker), and four were nonnative (channel
<br />catfish, common carp, red shiner, and fathead minnow; Table 3).
<br />Six native species and eleven nonnative species were collected in 1993
<br />(Table 2). The six native forms composed 82% of the total catch (17,994
<br />individuals). The most abundant native species was flannelmouth sucker (n =
<br />14,215, 64.7% of the total catch), followed by bluehead sucker (n = 2,814,
<br />12.8%), speckled dace (n = 931, 4.2%), flannelmouth X bluehead hybrids (n =
<br />30, 0.1%), mottled sculpin (n = 3, <0.1%), and Colorado squawfish (n = 1,
<br /><0.1%). No roundtail chub were collected during July or October 1993
<br />sampling. No razorback sucker were collected in 1993 (Table 3).
<br />Introduced species accounted for 18% of the total catch: channel catfish
<br />(n = 1760, 8.0%), common carp (n = 1538, 7.0%), red shiner (n = 509, 2.3%),
<br />and fathead minnow (n = 120, 0.5%). Seven other introduced species combined
<br />contributed 40 individuals to the total catch (Table 2). Of note among these
<br />was the capture of a grass carp (TL = 512 mm) at RM 104.3, just above Aneth,
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