Management Techniques 145 



as possible througliout the lake from surface to bottom. This can be done 

 by following a grid pattern which divides the lake surface into parallel 

 and crossing lines of treated strips (Figure 6.6). A fish has little chance 

 to escape the treated strips in the grid. 



Treatments for complete kills of fish should be made during seasons 

 when the surface water of the pond or lake is 70°F or higher, because, as 

 cited above, the efficiency of rotenone is much reduced in cold water. 



*lte * . <?^C^ -<i,g^. 





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:.-,mmHf&lt0^ ' 





Figure 6.5. Carp, bullheads, and green sunfish killed by rotenone treat- 

 ment of a small pond. 



Sometimes it is impossible to do a rotenone treatment during warm 

 weather; if such is the case, an extra amount of rotenone should be used 

 and special care should be taken in spreading it evenly. 



Where lakes and ponds to be poisoned contain significant numbers of 

 desirable fish, it is often practical to attempt their removal by seining or 

 the use of a boat shocker. These fish are stored in other waters during 

 the treatment and post-treatment period, and are restocked after the 

 rotenone has disintegrated. Sometimes water levels of lakes may be lowered 

 prior to treatment. Such a procedure is beneficial if it does not endanger 

 the survival of desirable fishes returned to the lake after treatment is 

 completed. Lowering the water level often increases the efficiency of 



