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6 Table 4. Percentage of n¢tiue fish in total catch and percentage of native species in total species taken in collec- tions with trammel nets from di f ferent locations in the upper Colorado River basin, 1974-76. Stations Total no. of fish caught Native fish (%) Total no. of species caught Native species (%- Lily Park (1) 483 78 9 44 Castle Park (2) 300 68 9 44 Echo Park (3) 628 73 12 50 Island Park (4) 190 88 10 50 Horseshoe Bend (5) 42 67 8 50 Ouray (6) 22 95 2 50 Sand Wash (7) 103 55 5 60 Walker Wildlife Area (8) 1,915 43 15 40 eSee Fig. 1 for locations of stations tions in 1974 and 1975 (Table 2-. However, during spring 1975, 14 additional razorback suckers were col- lected with electrofishing gear at station 3, from spawning bars in the lower Yampa River. Because electrofishing gear was used most extensively during the spring of 1975, direct comparison of relative abun- dance cannot be made with other collections. Flannelmouth suckers (Catostomus latipinnis) com- posed most of the catch made with nets and by elec- trofishing, occurring about 7 times more frequently than razorback suckers in the trammel net collections and 5 times more often in collections taken by electro- fishing. Bluehead suckers (C. discobolus) and roundtail chubs (Gila robusta) were also commonly collected at Echo Park. Native fish made up a smaller proportion of the total population in the gravel pit at station 8 than at any other site in the study area (Table 4-; razorback suckers totaled 0.8 to 4.2% of the catch at station 8 (Table 5~, which was roughly equivalent to that in the spring and fall collections at station 3. An important distinction is that they were present at station 8 Table 5: Percentage of fish of different species in collection made with trammel nets in the Walker Wildlife Area (station 8J, Colorado, 1974-76, and (where indicated) catch per unit of effort.e (See Fig. 1 for location of stations. peciesb Year, dates, and (in parentheses) total number of fish caught on those dates 1975 1976 3-10 April 24-28 May 15-17 June 12-16 April (543) (514) (600) (258) Percent CPEs Percent CPEs Percent CPEs Percent Catostomus latipinnis (N) 13.4 1.66 32.3 1.17 23.0 0.77 8.5 C. discobolus IN) 1.1 0.14 1.6 0.06 2.0 0.07 - C. commersoni 3.5 0.43 0.4 0.01. 1.7 0.06 4.7 Xyrauchen texanus (N) 4.2 0.52 2.9 0.11 0.8 0.04 1.6 Ptychocheilus lucius (N) 4.6 0.57 2.3 0.08 1.5 0.05 1.2 Gila robusta (N) 17.3 2.13 18.1 0.66 13.5 0.45 9.7 Cyprinus carpio 18.2 2.24 15.4 0.56 18.7 0.62 26.4 Prosopium williamsoni (N) - - 0.2 0.01 - - - Salmo gairdneri - - - - 0.2 0.01 - Lepomis cyanellus 16.0 1.97 5.4 0.20 21.5 0.72 7.8 L. m¢chrochirus 0.2 0.02 - - - - - Micropterus salmoides 7.7 0.95 1.6 0.57 2.7 0.09 13.6 Ictalurus punctatus 2.2 0.28 2.9 0.11 2.0 0.07 2.7 I. melas 11.2 1.38 16.9 0.61 12.5 0.42 23.6 Esox lucius 0.2 0.02 - - - - - eCPE =catch per unit effort; 1 unit of effort = 10 m of net (2.1 m deep) set for 10 h. Twenty-two razorback suckers were taken on 24 October-1 November and nine on 4-9 October 1975, but other fish caught were not recorded. bN =native species.