action over littoral areas influences year-class 

 survival of nest-building species by m ichanical 

 destruction of nests (Kramer and Smitn, 1962). 

 Increased turbidity decreases production of 

 plankton necessary for fish food and fish growth 

 (Buck, 1956). The poor growth found for many 

 fishes in Lewis and Clark Lake compared to 

 growth attained by these same species in Fort 

 Randall and Oahe Reservoirs may be related to 

 differences in water depth and turbidity. The 

 waters of both Oahe and Fort Randall Reservoirs 

 are relatively deep and clear and therefore less 

 influenced by surface winds , while Lewis and 

 Clark Lake is shallow and turbid. 



The fish population of Lewis and Clark 

 Lake did not appear to attain stability during the 

 period of study. Most species produced a large 

 year -class in 1956 and this group more or less 

 dominated the adult population complex through 

 1962 . The population produced with the present 

 schedule of reservoir water management will 

 probably be dominated by river carpsucker, carp, 

 and freshwater drum . The predominant sport 

 fishes will probably be white crappie, sauger, 

 channel catfish, and perhaps white bass. Future 

 abundance of individual species will be dependent 

 on spawning success and survival which may be 

 influenced by alterations in the pattern of water 

 level fluctuation, 



SUMMARY 



The fish population of Lewis and Clark 

 Lake has been studied since 1956, following 

 closure of Gavins Point Dam on July 31, 1955. 

 Investigations were conducted by the South 

 Dakota Department of Game, Fish, and Parks 

 from 1956 to 1961 and continued by the Bureau 

 of Sport Fisheries and Wildlife in 1962. The 

 purpose of these studies was to monitor the 

 development of the fish population so that prac- 

 tical management measures could be formulated. 

 This report summarizes the results of these in- 

 vestigations . 



The reservoir has a maximum surface area 

 of 33,000 acres, is 37 miles long and averages 

 2 miles wide. Its depth ranges from 45 feet near 

 the dam to less than 6 feet in its upper extremity. 

 Total shoreline is 100 miles, and storage capacity 



is 540,000 acre -feet. Lake level is maintained 

 between 1,204 and 1,208 feet m.s.l. under 

 normal operational conditions . The reservoir 

 is characterized by rapid exchange of water, 

 and during spring and summer the entire storage 

 is passed through the dam every 8 to 10 days. 

 During the winter, complete exchange is possible 

 every 30 days. Dissolved oxygen, water temper- 

 ature, alkalinity, and pH were satisfactory for 

 warm-water fishes. Secchi-disk visibility ranged 

 from 3 inches in the extreme upper reservoir 

 to 3 feet near the dam . 



Fish were collected by gill nets, frame 

 nets, and shore seines. Scale samples, total 

 length, weight, sex, and maturity were obtained 

 for fish collected at each station by each sampling 

 method. Collections by shore seine were pre- 

 served and returned to the laboratory for further 

 study. Methods of investigation used by personnel 

 of the South Dakota Department of Game, Fish, 

 and Parks and the Bureau of Sport Fisheries and 

 Wildlife were similar. 



Numbers of fish collected by gill and frame 

 nets in June, July, and August, 1956 through 1962, 

 were used to determine trends in relative abun - 

 dance of those fish vulnerable to capture by these 

 gear. Thirty-three species, exclusive of minnows, 

 were collected during these years . Most abundant 

 fishes were carp, river carpsucker, and white 

 crappie. Other major species, not in order of 

 abundance, were shovelnose sturgeon, shortnose 

 gar, s ma 11m outh buffalo , channel catfish, black 

 crappie, sauger, and freshwater drum. The 

 following species disappeared or were rare 

 following impoundment: pallid sturgeon, paddle - 

 fish, longnose gar, rainbow trout, blue sucker, 

 blue catfish, stonecat, black bullhead, northern 

 pike, burbot, green sunfish, and orangespotted 

 sunfish . 



Relative annual abundance of major species 

 was determined by comparison of the average 

 catch per unit of effort of each type fishing gear . 

 Apparent abundance of most fishes declined between 

 1956 and 1962. Marked decreases were suggested 

 for shovelnose sturgeon, carp, and black crappie. 

 White and black crappie experienced wide fluctu- 

 ations in abundance , and in 1962 both were at a 

 low level with white crappie predominating. 



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