WATER SUPPLY 



4. Ponds should be constructed in such 

 a way that they can be drained com- 

 pletely, emptied of fish, and refilled 

 when necessary. 



Water supply 



A suitable and an adequate water 

 supply is of primary importance, 

 and should be considered first in 

 selecting a site for rearing ponds. 

 To be suitable, the water should be 

 only moderately hard and should 

 contain no other species of fish ; the 

 temperature of the water should be 

 high enough to promote rapid 

 growth (see p. 69) ; the pH, or hy- 

 drogen-ion content, should be 

 slightly on the alkaline side. 



Springs and artesian wells are 

 the most desirable source of supply 

 because such water is dependable, 

 easily controlled, permanently clear, 

 and generally free from pollution. 

 A water supply should be protected 

 from contamination by surface 

 water, which may cause the supply 

 to become turbid or polluted by 

 drainage from stables, yard ponds, 

 and like sources, as well as from con- 

 tamination iby insecticides, fungi- 

 cides, and herbicides. 



Hard water may be undesirable 

 because it generally contains nox- 

 ious gases, such as carbon dioxide, 

 nitrogen, hydrogen sulfide, and 

 marsh gas. All of these gases are 

 injurious to fish by actually poison- 

 ing or asphyxiating them. Other 

 waters may contain excessive quan- 

 tities of iron. In nearly all of 

 these instances, the water can be 

 purified and made suitable for fish 

 by running it over a series of falls. 



or baffles, and by storing it in a 

 reservoir with a large surface area 

 to permit thorough aeration. 



Spring and artesian water should 

 be tested beforehand by placing 

 fish in it. A temporary pond or 

 trough may be employed for the 

 purpose. If possible, the fish 

 should be held in the pond or 

 trough for a whole season to ob- 

 tain a good test ; however, a shorter 

 period, perhaps a month, may be 

 sufficient. If the fish remain 

 alive, the water can be considered 

 suitable. 



Permanent construction should 

 include a reservoir at or below the 

 spring itself. This reservoir may 

 be of concrete, or riprapped with 

 stone or brick for protection. A 

 way must be provided so that ex- 

 cess w^ater from the supply can 

 be diverted around the pond or 

 ponds. A sufficient flow should be 

 provided to compensate for seep- 

 age and evaporation from the 

 ponds during the propagation 

 season. 



Natural w^ater supplies, such as 

 creeks, lakes, rivers, or ponds, may 

 be utilized as a source of water, 

 but should be considered only 

 when springs or artesian supplies 

 are not available, or where the nat- 

 ural sources have all the necessary 

 attributes of a good w^ater supply. 

 These sources are subject to change 

 in volume, temperature, and tur- 

 bidity, and may be polluted. In 

 addition, they generally contain 

 undesirable species of fish which 

 prey on minnows and reduce pro- 

 duction in the ponds. No hatch- 



