144 Theories and Techniques of Management 



a; 



Q 



53 50 







Temperature F 



Figure 6.4. Selective poisoning of warm-water fish in trout ponds in Mas- 

 sachusetts by the use of rotenone. Tests indicated that the rotenone did not 

 penetrate below the zone of rapid-temperature transition at 30 to 35 feet. 

 Trout that remained at depths below about 35 feet were unaffected, while 

 most of the warm-water fish above 30 feet were killed. [From Thompkins, 

 W. A., and Mullan, J. W., Prog. Fish-Cult., 20 ( 3 ) ( 1958 ) ] 



