8257 - Laserfiche WebLink

Home Browse Search

Table 3. Altemating cUITent electrofishing catch of sauger from the Missouri River, Nebraska, 1964, 1975, and 1990. Channelized, Channelized, Unchannelized, Year % of all fish sauger/h sauger/h 10.0 10.0 3.0 3.3 0.3 0.5 1964 1975 1990 11.0 1.6 has been good this year but last winter was much better with a larger take of sauger." Channelization of the river south of Omaha be- gan in the late 1930's, but not until the late 1950's, north of Omaha. Scientific surveys were first im- plemented as channelization commenced in the 1950's, and Robinson (1958a) note.d a "marked dif- ference in the composition of eleclrofishingcatches" north of Omaha, although he did not elaborate on the southern catch. However, main channel catches during 27.5 h of electrofishing (north of Omaha), included 138 (7%) sauger, 119 (6%) largemouth bass, and 148 (7.5%) crappie. Morris (1965) cap- tured 10 sauger/h of electrofishing (10% composi- tion) near Blair (north of Omaha; Table 3). During 1971-75, 16,418 fish were electrofished near Blair; 450 (2.7%) saugerwere collected, and the catch rate had dropped in 3.3/h of electrofishing (Hesse and Wallace 1976). During 1986-90 we electrofished8.5 h at Blair, and collected 500 fish; none was sauger. We electrofished 40 additional hours during this same period at six other sites in the channelized section and collected 2,214 fish; 13 (0.6%) were sauger (0.3/h). In 1964, Morris (1965) averaged 11 sauger/h with a boatshocker in the unchannelized Missouri River near yankton, South Dakota (downstream from Gavins Point Dam; Table 3). Between 1983 LARRY W. HEsSE ET AI. 333 and 1990 we electrofished 48.7 h at St. Helena (Cedar County), which is about 8 k:m. from Monis's collection site. We collected 1,681 fish; 80 (4.8>Al) were sauger, and the catch rate was 1.6/h. How- ever, only five sauger were collected at St. Helena after 1984 (53 in 1983, 22 in 1984). Four other sites on the unchannelized reaches upstream and down- stream from Gavins Point Dam and Lewis and Clark Lake were electrofished between 1983 and 1990; 221 sauger (6.4%) were among 3,455 cap- tured fish, and the catch rate was 1.9/h. Experimental gill nets have been used in collect fish in }'P.mnaI'lt backwaters of the Missouri River since 1983. These areas are rare and exist mostly in the unchannelized reach upstream from Lewis and Clark Lake. 'Th.e sauger catch rate has declined steadily from 4.5/gillnet-night in 1983 in 0.3/gill- net-night in 1991 (Table 4).Sauger, as a percent of intal fish composition, also steadily declined from 19.4% in 1983 to 4.4% in 1991. The mean CPUE for a year was compared with the following year in a t-test, and the annual decrease in CPUE was shown to be significantly different (P = 0.05). Collection of larval fish also provided some in- sight inin the decline of sauger in the Missouri River. We have collected more than 112,000 larval fish since 1983 (not including a large number from the Gavins Point Dam tailwater), and larval sauger density varied from 0.1 to 2.2/1,000 mB (mean = 0.9) in the reach upstream from Lewis and Clark Lake. Nelson (1968) reported that larval sauger density in 1965 was 10.6/1,000 mB in this same reach. Mean larval sauger density in the chan- nelized section for 1986-91 was 1.1/1,000 mB. Some or most of these may have drifted from the unchannelized section downstream from Gavins Point Dam, where mean larval sauger density was 2.3 for 1983-91. Sauger larvae composed 1.8% of all Table 4. Experimental gillnet catch of sauger from the unchannelized Missouri River, Nebraska, during 1983-91. Total fish Total Total Sauger Year captured CPUE sauger Sauger % CPUE 1983 396 6.8 77 19.4 4.5 1984 393 6.7 59 15.0 3.3 1985 558 7.3 81 14.5 2.8 1986 280 7.4 20 7.1 2.0 1987 27 3.5 3 11.1 0.8 1988 501 3.8 5 1.0 0.2 1989 38 8.5 0 0.0 0.0 1990 164 5.8 0 0.0 0.0 1991 138 3.2 6 4.4 0.3