Fish Hatchery Management - fisheries & aquaculture

FISH HATCHERYMANAGEMENTFIcunn 110. Aerator-oxygen system designed and tested by FWS personnel atAlchesay National Fish Hatchery, New Mexico. (l) Aerators mounted on top ofan aluminum tank. Note the electrical line for the l2-volt system. (2) Aeratorwith a dual manifold extending through the false bottom of a tank. Water ispulled through manifold (M) ana discharged through aerator (e). (g) Aerator inoperation. Water is aerated and circulated and carbon dioxide is removed. (4)The false bottom of the tank has been removed to show micropore tubing(arrow) which disperses oxygen into the water. Note bubbling of oxygen throughthe water. (Photos courtesy Alchesay National Fish Hatchery, FWS.)levels must remain within a tolerable range, and toxic levels of dissolvedammonia and carbon dioxide must be suppressed. A partial solution to thiscomplex problem is aeration by sprays, baffles, screens, venturi units,compressed gas liberation, agitators, or air blowers. Bottled gaseous orliquid oxygen is liberated within tanks in a variety of ways, including perforatedrubber tubing, carborundum stones, carbon rods, and microporetubing, or is injected directly into the recirculation system.Recent aeration innovations include a miniature water wheel that aerateswater during transport and the Fresh-flo@ aerator. The latter is commerciallyavailable in ten sizes. The system depends upon centrifugal forcecreated by a high speed motor-driven impellor that pulls water into a systemof vanes, producing the turbulence needed to mix water with air,while concurrently rernoving carbon dioxide. This aerator has been highlysatisfactory for transportation of warmwater fish and salmonids.