6 8 10 



TOTAL LENGTH 



state. Near Horseshoe Lake this water left the 

 channel of the Cache to enter the Mississippi at Dog 

 Tooth Bend. At the time of the flood it seemed likely 

 that Horseshoe Lake might have lost a large part of 

 its fish or that objectionable species might have 

 moved in. The 1937 survey was made to determine 



Left. — The black crappie made up 37 percent of all fish 

 taken in hoopnets by the four surveys. 1934-1938. A huge 

 brood of black crappies was spawned in the spring of 1932 

 from breeding stock placed in the lake a few months earlier. 

 This brood grew at a normal rate during its first two years, 

 reaching an average total length of 6 inches by the spring 

 of 1934. After that, growth was retarded by dwindling 

 food supplies. These fish reached an average length of 

 8 inches by 1936 and since then have not grown at all. 

 Moderate reductions in the numbers of this 1932 brood from 

 year to year have not resulted in increased growth among 

 the survivors because of increasing competition by the 

 white crappies. The black crappie, more than any other 

 fish, has been responsible for destroying the young, not 

 only of its own kind, but also those of most other species 

 in the lake. 



what changes the flood had made. We found no evi- 

 dence that Horseshoe Lake had lost any of its fish. 

 The only intruders were two spotted gars. Up to this 

 time this species had not been taken in the lake, 

 although it is present below the spillway. No sf)otted 

 gars or other newcomers were caught in this spring's 

 survey. If this flood had taken place in warm 

 weather when fish are active, it seems certain that 

 the fish population of Horseshoe would have been 

 greatly disturbed and mixed up. Throughout the 

 early part of the flood, the quieter waters were cov- 

 ered with ice and at no time did the temperature rise 

 more than a few degrees above freezing. It appears 

 that the fish of Horseshoe and vicinity lay quietly 

 while the fiood waters rose and went down again. 



Largemouth Black Bass 



Two of the diagrams show the essential facts about 

 the largemouth bass in Horseshoe Lake. 



When the lake was visited in May of 1932, as 

 many as a quart of Gambusia could be taken in a 

 short haul with a minnow seine, together with bass 

 fry about an inch long and large numbers of fry 

 of the flier sunfish. The top minnows and the fry 

 of the flier sunfish probablj- made up the bulk of 

 the food of the bass that first year and were responsi- 

 ble for their rapid growth. When the lake was 

 visited in the summer of 1933 it was noted that the 

 bass were growing very rapidly. The decline in the 



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Largemouth Black Bass 

 D Av OF All data (ill,Wis.nebr,La_) 



AV OF 328 FROM HORSESMOe LAKE 



ui 



1st 2nd 



Jl Di D. D D D D 



3rd 4TH 5th 6TH Tm 8tm 9th IOtm 

 YEAR OF LIFE 



After Horseshoe Lake was rebuilt, food was at first abun- 

 dant. The bass responded to this favorable condition more 

 readily than other species and grew very rapidly. At an 

 age of one year they were almost twice as long and weighed 

 six times as much as the average yearling bass in the 

 Mississippi Valley. Increasing competition by crappies re- 

 duced growth in the bass to normal in their second year, 

 then below normal, finally almost to zero. At the present 

 time these bass are living on a subsistence basis. 



