Fish Hatchery Management - fisheries & aquaculture

32 FISH HATCHERY MANAGEMENTFIGURE 15.(l) A vacuum liquid manure spreader with a modified hose connectioncan be used to remove settleable waste solids from fish rearing units.(Z) Water flow is controlled with a f -turn ball valve (arto*). The valve is shutoff whenever the cleaning wand is not actually drawing up waste. Note the settlingarea providedsolids are then spread on agriculture(Fws photos.)at the lower end of the raceway. (3) The collected wastelands or lawn areas away from residences.Hatchery DesignIn judging the suitability of a site for a fish hatchery, the primary purposeof the hatchery should be considered. If egg production is an importantfunction, somewhat lower temperatures may be desirable than if thehatchery is to be used primarily for rearing fish to catchable size. Whereno eggs are handled even higher water temperatures may be desirable toafford maximum fish growth.For efficient operation of a hatchery, the site should be below the watersource. This will afford sufficient water head to provide aeration and adequatewater pressure without pumping. Site considerations should also includesoil characteristics and land gradient. An impervious soil will holdwater with little seepage. Land that is sloped provides drainage and allowsthe construction of raceways in a series for reuse of water by gravity flow.Possible pesticide contamination of the soil and the presence of adjacentland use that may cause agricultural or industrial contamination should beinvestigated. Flood protection is also essential.