68 FISH CULTURE 



to be avoided, because of the difficulty in han- 

 dling the nets when fish are to be removed, un- 

 less it is possible to draw off all the water for 

 that purpose. 



The character of the sides and bottoms of the 

 ponds for cat-fish culture is important. When 

 ponds are built for most types of fishes the bot- 

 toms are gravelled, and in some instances 

 trout-culture for example the sides are walled 

 with boards, stone or concrete; but ponds for 

 cat-fish must have the banks and bottoms of 

 clay, at least those portions where the fish 

 spawn. The kettle, or deep portion, if not of 

 clay, may be of heavy mud, but not too deep. 



There are two reasons for this : first, the clay 

 banks and bottoms are essential as nest-building 

 and spawning places ; second, during the winter 

 months cat-fishes burrow to a greater or less 

 extent. They cannot do this where the bottom 

 is gravelly. 



Two feet is a sufficient depth for the shelf, 

 although two and one-half or even three feet 

 is more desirable. The kettle should be from 

 five to six feet deep. Cat-fish do better where 

 the water is not too shallow, and for this reason 



