SELECTION OF FISHES 33 



is small enough, about 1.5 inches, that only the most 

 limited facihties are required. Its shortcomings in- 

 clude being too small to be injected or to be weighed 

 conveniently. Like most "tropicals" the zebra should 

 be maintained at a temperature of 75° to 80° F. 



To spawn this species, one should place several 

 males and females in a cage of nylon marquisette 

 suspended in an aquarium. Water depth in the tank 

 should be only three or four inches. The cage should 

 be suspended approximately one inch above the bot- 

 tom of the tank. When the fish spavvoi, the eggs fall 

 through the netting and escape being eaten. Zebras 

 may also be spawned over gravel, but a large tank is 

 required. 



Bullheads (Ictalurus spp.) are available in most 

 areas of the United States. They can be held in 

 aquaria but are especially recommended for short 

 term studies involving bringing experimental fishes in 

 from the field. Bullheads will feed on meats or meals. 

 They respond negatively to hght and are probably 

 more suitable as experimental fish when kept in sub- 

 dued fight. In smaU ponds bullheads tend to become 

 very numerous, and by seining one may frequently 

 obtain large numbers of uniform size. 



There exists considerable interest in the culture of 

 channel catfish (Ictalurtts punctatus). This has re- 

 sulted in the accumulation of knowledge concerning 

 this species and has made channel catfish of all sizes 

 available commercially. Notable among the areas 

 where this culture is being practiced are Arkansas and 

 Mississippi. Eggs of the channel catfish can be ob- 

 tained by use of fish pituitary extract or even chorionic 

 gonadotrophin. Catfish can be crowded and fed 



