Management Techniques 141 



ficient size and depth to hold fish. Such an arrangement was used at 

 Ridge Lake where, in cool weather, all of the larger fish from 18 acres 

 of water could be held for several days in a concrete stilling basin 70 

 feet wide, and 30 feet long, with a maximum depth of 4 feet when the 

 basin was pumped fulL^^ Where no holding basin is available near the 

 outlet, arrangements should be made to hold the fish in portable tanks of 

 metal or canvas or in nearby ponds, a count being kept of the fish moved 



Figure 6.3. Small Wolf-type weir built across the concrete flume below 

 drain valve for 2.5-acre pond. This weir will handle a comparatively large flow 

 of water and allow capture of the fish alive because water drops through the 

 bottom screen as well as flowing through the sides. 



to these ponds. Later, when a small amount of water has become im- 

 pounded in the drained lake basin, fish in the tanks may be returned or, 

 those released in the ponds may be recollected by seining. The cool days 

 of early spring and late fall are best for lake draining operations, because 

 fish can be handled at these times with a minimum of loss. 



Most lakes and ponds will not drain completely, and it is usually neces- 

 sary to treat the water remaining in pockets or channels in the basin with 

 some chemical to kill the small fish that may remain in this water and 

 escape to the lake as the basin refills. For this purpose one can use H.T.H. 



