80 MAINTAINING FISHES 



the development of satisfactory materials for the ad- 

 sorption of ammonia but starvation of fishes prior to 

 transporting, and mechanical filtration are probably of 

 value in reducing the production of ammonia. 



Particulate Wastes 



When transported, fishes frequently regurgitate 

 and may also produce excess quantities of mucus. 

 These materials plus fecal matter result in the water 

 of transport tanks becoming badly fouled. As a result 

 of bacterial decay the fouled water will exhibit a de- 

 crease in oxygen and an increase in carbon dioxide 

 and ammonia. When fishes are to be crowded for a 

 long period of time, some means of removing particu- 

 late wastes is desirable. Various mechanical strainers 

 have been incorporated into water circulating sys- 

 tems. The system which shows the greatest promise is 

 the diatomaceous earth filter used for filtering the 

 water of swimming pools. Such a filter is capable of 

 removing fine particles and is relatively easy to re- 

 charge (Norris, Brocado, Calandrino, and McFarland, 

 1960). 



Use of Anesthetics in Transporting of Fishes 



The metabolic rate of stimulated fishes is thought 

 to be four to five times greater than that of the basal 

 rate (Fry, 1957). By use of anesthetics it is possible 

 to reduce the "activity" metabohc rate to the basal 

 rate. Thus by use of anesthetics it is theoretically 

 possible to increase the weight of fish hauled four to 

 five times that which would be possible under normal 

 conditions. McFarland (1960) is of the opinion, how- 

 ever, that due to the effects of an excess of pounds of 



