16 FISH HATCHERY MANAGEMENT 



Water Supply and Treatment 



An adequate supply of high quality water is critical for hatchery opera- 

 tions. Whether fish are to be cultured intensively, requiring constant water 

 flow, or extensively, requiring large volumes of pond water, the water supply 

 must be abundant during all seasons and from year to year. Even 

 hatcheries designed to reuse water need substantial amounts of "make-up" 

 flow. Among other criteria, hatchery site selection should be based on a 

 thorough knowledge of local and regional hydrology, geology, weather, and 

 climate. 



Groundwater generally is the best water source for hatcheries, particu- 

 larly for intensive culture. Its flow is reliable, its temperature is stable, and 

 it is relatively free of pollutants and diseases. Springs and artesian wells are 

 the cheapest means of obtaining groundwater; pumped wells are much less 

 economical. 



Spring-fed streams with a small watershed can give good water supplies. 

 They carry little silt and are not likely to flood. The springs will ensure a 

 fairly steady flow, but there still will be some seasonal changes in water 

 temperature and discharge; storage and control structures may have to be 

 built. It is important that such streams not have resident fish populations, 

 so that disease problems can be avoided in the hatchery. 



Larger streams, lakes, and reservoirs can be used for fish culture, but 

 these vary considerably in water quality and temperature through the year, 

 and may be polluted. They all have resident fish, which could transmit 

 disease to hatchery stocks. 



Even though the water supply may be abundant and of high quality, 

 most hatcheries require some type of water treatment. This may be as sim- 

 ple as adjusting temperatures or as involved as treating sewage. Excluding 

 management of pondwater quality, discussed in Chapter 2, and medication 

 of diseased fish (Chapter 5), water may have to be treated at three points 

 as it passes through a hatchery system: as it enters; when it is reused; and 

 as it leaves. 



Treatment of Incoming Water 



Water reaching a hatchery may be of the wrong temperature for the fish 

 being cultured, it may have too little oxygen or too many suspended solids, 

 and it may carry disease pathogens. These problems often are seasonal in 

 nature, but sometimes are chronic. 



TEMPERATURE CONTROL 



The control of water temperature is practical when the amount of water to 

 be heated or cooled is minimal and the cost can be justified. Temperature 



