A Classification of the Biological States of 

 Waters and of Fish-holding 

 Procedures 



FISHES ALTER the watei in which they live. They 

 remove dissolved oxygen and contaminate the water 

 with fecal, respiratory, and urinary wastes. When 

 fishes are fed nonliving food, the water is further 

 contaminated by soluble components of the food as 

 well as any uneaten portion of nonsoluble constit- 

 uents. There is, of course, a direct relationship be- 

 tween the degree of crowding of the fishes and the 

 extent to which the water is contaminated or altered. 

 The different contaminants affect the water in dif- 

 ferent ways. Fecal and imutilized food materials 

 cause the water to become turbid, cause a build-up of 

 carbon dioxide and ammonia, and increase the num- 

 ber of decay organisms, especially bacteria. If un- 

 usually abundant, these organisms can seriously 

 reduce the dissolved oxygen content. Some of the 

 saprophytes such as the water molds Saprolegnia spp, 

 may become parasitic on the fishes or their eggs. 



