32 FISH HATCHERY MANAGEMENT 



Figure 15. (l) A vacuum liquid manure spreader with a modified hose connec- 

 tion can be used to remove settleable waste solids from fish rearing units. 

 (2) Water flow is controlled with a j-turn ball valve (arrow). The valve is shut 

 off whenever the cleaning wand is not actually drawing up waste. Note the set- 

 tling area provided at the lower end of the raceway. (3) The collected waste 

 solids are then spread on agriculture lands or lawn areas away from residences. 

 (FWS photos.) 



Hatchery Design 



In judging the suitability of a site for a fish hatchery, the primary purpose 

 of the hatchery should be considered. If egg production is an important 

 function, somewhat lower temperatures may be desirable than if the 

 hatchery is to be used primarily for rearing fish to catchable size. Where 

 no eggs are handled even higher water temperatures may be desirable to 

 afford maximum fish growth. 



For efficient operation of a hatchery, the site should be below the water 

 source. This will afford sufficient water head to provide aeration and ade- 

 quate water pressure without pumping. Site considerations should also in- 

 clude soil characteristics and land gradient. An impervious soil will hold 

 water with little seepage. Land that is sloped provides drainage and allows 

 the construction of raceways in a series for reuse of water by gravity flow. 

 Possible pesticide contamination of the soil and the presence of adjacent 

 land use that may cause agricultural or industrial contamination should be 

 investigated. Flood protection is also essential. 



