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<br />frequency of backwaters was still less than two per five-mile segment in 1987, 1988, and 1991. <br />Only in 1990 were two backwaters available for sampling per five-mile segment. A summary of <br />the sampling effort and resulting gamefish numbers collected shows inclusion of the 15-mile reach <br />in the sampling effort in 1987, 1988, and 1991 almost doubled the number of backwaters available <br />for sampling (Table 1). Area of backwaters sampled in the study reach was regarded to be an <br />close approximation of backwater habitat available overall due to the scarcity of backwaters <br />available for sampling. Area seined ranged from 5.3 % of available habitat in 1990 to 11.9% in <br />1991. Clearly the 25 % sample area per backwater criterion was not met using two seine samples <br />per backwater under ISMP protocol. Despite differences in effort between years, river miles <br />sampled, number of backwaters sampled, and number of seine hauls made per year, these indices <br />of effort did not correlate significantly with yearly estimates of backwater habitat available or area <br />seined. Pearson correlation coefficients (r) for seine number and seine area (r=0.76), backwater <br />number and backwater area (r=0.22), seine area and backwater area (r=0.61), and river miles <br />sampled and backwater area (r=0.22) were not significant at P=0.05 (n=6, r>0.811 at po.os and <br />df=4). <br /> <br />Numbers of fish collected and relative composition for both gamefish species as a group <br />and for all other fish species differed greatly in ISMP fall seine samples. The relative abundance <br />of nonnative gamefish species appeared to be minor in comparison to all the fish species collected <br />during seine sampling (Figure 1.A). After sampling 95 backwaters with 198 seine hauls over six <br />years only 684 gamefish were collected, or 1 % of the 63,709 fish collected (Table 1). Five native <br />fish species and 13 nonnative fish species were collected in the seine samples and ranged from <br />2,208 fish collected in 1986 to a peak of 23,684 fish collected in 1988. During 1986-1991, two <br />nonnative cyprinid fish species, red shiner and fathead minnow, clearly were numerically <br />dominant every year. These two species made up 69-97% of the fish sampled. If sand shiner is <br />included, these percentages increased to 71-99 %. When red shiner numbers were relatively low <br />in 1986-1988, fathead minnow numbers were high (Figure 1.A). In 1989 when fathead minnow <br />numbers decreased, red shiner numbers increased. The percentages of red shiner and sand shiner <br />appeared to increase over this six-year period, which compensated for decreases in fathead <br />minnow percentage. Mosquitofish demonstrated a small relative increase in relative abundance <br />in 1990 (Table 1). <br /> <br />Six nonnative gamefish species collected ranged from 0.6-3.2 % of the total number of fish <br />sampled in 1986-1991, and appeared to be decreasing from 1987 to 1991 (Figure 1.A and 1.C). <br />Green sunfish was the most prevalent centrarchid species over the six-year period. A peak in <br />relative abundance for nonnative gamefish occurred in 1987, when green sunfish and largemouth <br />bass comprised the bulk: of the gamefish collected. Green sunfish and ictalurids comprised the <br />bulk: of nonnative game fish collected during 1988-1991. Black crappie and bluegill catches in <br />1987 and 1988, respectively, were incidental. By comparison, relative abundance of native fish <br />species peaked at 26.3 % in 1986 (Figure 1.A and 1.B). This peak was followed by declines in <br />1987 to 1990. The relative abundance of native fish was only 1 % in 1991. Bluehead sucker, <br />roundtail chub, and speckled dace numbers were responsible. for the peak in native fish relative <br />abundance in 1986. Roundtail chub alone was responsible for the bulk: of the native fish collected <br /> <br />8 <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />