Fish Hatchery Management - fisheries & aquaculture

l6FTSH HATCnltRy NIANAcENlltNtWater Supply and TreatmentAn adequate supply of high quality water is critical for hatchery operations.Whether fish are to be cultured intensiaej, requiring constant waterflow, or extensiuely, requiring large volumes of pond water, the water supplymust be abundant during all seasons and from year to year. Evenhatcheries designed to reuse water need substantial amounts of "make-up"flow. Among other criteria, hatchery site selection should be based on athorough knowledge of local and regional hydrology, geology, weather, andclimate.Groundwater generally is the best water source for hatcheries, particularlyfor intensive culture. Its flow is reliable, its temperature is stable, andit is relatively free of pollutants and diseases. Springs and artesian wells arethe cheapest means of obtaining groundwater; pumped wells are much lesseconomical.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 afairly steady flow, but there still will be some seasonal changes in watertemperature and discharge; storage and control structures may have to bebuilt. 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, butthese vary considerably in water quality and temperature through the year,and may be polluted. They all have resident fish, which could transmitdisease 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 simpleas adjusting temperatures or as involved as treating sewage. Excludingmanagement of pondwater quality, discussed in Chapter 2, and medicationof diseased fish (Chapter 5), water may have to be treated at three porntsas it passes through a hatchery system: as it enters; when it is reused; andas it leaves.Treatment of Incoming WaterWater reaching a hatchery may be of the wrong temperature for the fishbeing cultured, it may have too little oxygen or too many suspended solids,and it may carry disease pathogens. These problems often are seasonal innature. but sometimes are chronic.TEMPERATURE CONTROLThe control of water temperature is practical when the amount of water tobe heated or cooled is minimal and the cost can be justified. Temperature