Fish Hatchery Management - fisheries & aquaculture

FISH HA'I'CHERY MANAGEMENTponds' especially on how well the water is naturally buffered with bicarbonates.Agricultural extension agents and the Soil conservation servicecan provide detailed advice about water chemistry and lime applications.Normally, a limed pond will be safe for stocking within l0 days aftertreatment, or when the pH has declined to 9.5. However, a normal foodsupply will not be present until three to four weeks later.Chlorine has been used by fish culturists as a disinfecting agent. Tenparts per million chlorine applied for 24 hours is sufficient to kill all harmfulbacteria and other organisms. Several forms of chlorine can be obtained.Calcium hypochlorite is the most convenient to apply. It contains 700iichlorine and is readily available. It can be applied to either flooded ordewatered ponds.A 600 parts per million solution of Hyamine 1622, Roccal, or Hyamine3500 may be used for disinfecting ponds. Twice this strength may be usedto disinfect equipment and tools. The strength of the disinfecting solutionis based on the active ingredient as purchased.Water Supply StructuresThe water supply for a fish hatchery should be relatively silt-free and devoidof vegetation that may clog intake structures. For this reason, anearthen ditch is not recommended for conveying water because of algalgrowth and the possibility of aquatic vegetation becoming established. Athatcheries with a silt problem, a filter or settling basin may be necessary.The water intake structure on a stream should include a barred grill to excludelogs and large debris and a revolving screen to remove smaller debrisand stop fish from entering the hatchery.There are a vast number of methods used to adjust and regulate waterflows through fish rearing units. some of these include damboards, headboxeswith adjustable overflows, headgates, headboards with holes boredthrough them, molasses valves, faucet- type valves, and flow regulators.Each type has advantages.Generally, damboards and headboxes will not clog, and they provide asafe means of regulating water flows. They are particularly useful withgravity water supplies, but they are not easily adjusted to specific waterflows. valves and flow regulators are readily adjustable to specific waterflows and are preferred with pressurized water supplies, but are prone [oclogging if any solid material such as algae or leaves is present in thewater.water flows can be measured with a pail or tub of known vorume and astop watch when valves or gates are used to regulate the water flow. Damboards can be modified to serve as a rectangular weir for measuring flows(Appendix D).