7956 - Laserfiche WebLink

Home Browse Search

.. ,~. ~ - . Fourteen other species were caught during YOY squawfish monitoring (Table 6). Two other species of native fish (Catostomus sp. and Gila sp.) were encountered (Table 7). Suckers were the most numerous native species caught in 1992 and 1994 and second most numerous in 1993. Their numbers and CPUE varied in opposition to those of squawfish (Figure 12). Gila sp. were second most numerous in 1990, 1991 and 1994, but never numbered more than S I individuals caught. Variations in numbers and CPUE for chubs mimicked that of squawfish (Figure 12). Non-native fish were much more common than native fish in all years except 1991, when they were least prevalent of any reporting year (Table 7). Red Shiners were the most numerous species, followed by fathead minnows. Sand shiner numbers were highly variable, but greater than native fish in 1992 and 1994. Mean CPUE for non- native fish varied even more than that for native fishes. Red shiner CPUE ranged from 2.69 fish/ 100 m2 in 1991 to 902 fish/ 100 m2 in 1994. Fathead CPUE ranged from 0.28 fish/ 100 m2 in 1991 to 66 fish/ 100 m2 in 1994. Sand shiner captures surpassed fathead only in 1994 (96 fish/100 m2). There was no relationship between variations in CPUE for these fish and the native fishes (Figure 12}. Although flows are thought to have the greatest impact on fish production in the Green River, it is~clear from these five years data that other factors influence production. For example, flow and run-off events were very similar in 1991 and 1994, but squawfish numbers and growth were drastically different. Likewise, there was no definitive relationship between mean CPUE for the five other fish species recorded and flow conditions. Considerable concern exists about the effect of non-natives (predation and competition) on native fish production. If competition were a direct contributing factor in determining growth and survival of native fishes, native fish and non-native fish numbers should vary in opposition. The data presented do not indicate this. squawfish and chub production appeared to vary in inverse to sand shiners, but this did not follow for the 2 other non-native species sampled. In fact, the data seem to indicate a negative relationship between sucker and squawfish numbers. RECOMMENDATIONS Continued monitoring is necessary to ascertain population status of Colorado squawfish in the Green River. Increased catches of adult fish in 1994 could be an indication of strong recruitment from the 1986 year class and the beginning of recruitment from the high productivity year of 1988. Strong recruitment from these year classes is important for future population growth. In addition, continued adult monitoring will allow researchers to ascertain strength and survivorship of the 1991 year class, the third most productive year since 1986. Lastly, it will be important to determine 28