Location: Warmwater Aquaculture Research UnitTitle: Dissolved oxygen and aeration in ictalurid catfish aquaculture Author
Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2017
Publication Date: 2/2/2018
Citation: Boyd, C.E., Torrans, E.L., Tucker, C.S. 2018. Dissolved oxygen and aeration in ictalurid catfish aquaculture. Journal of the World Aquaculture Society. 49(1):7-70.
Interpretive Summary: Feed-based catfish farming in ponds is the largest aquaculture sector in the United States. Although using manufactured feed can support high levels of fish production, feed use has the unintended consequence of imposing a large oxygen demand that often exceeds the capacity of natural processes to maintain adequate dissolved oxygen for best fish growth, health, and survival. Mechanical aeration is therefore a critical practice in catfish farming. This paper summarizes the behavior of oxygen in water, catfish pond dissolved oxygen budgets, the physiology of hypoxia in catfish, the history of aeration research and development in catfish farming, aerator use in ponds, aeration in catfish hatcheries, and dissolved oxygen measurement. Although this paper focuses on the US catfish industry, the findings are applicable to feed-based aquaculture in all types of aerated ponds.
Technical Abstract: Feed-based production of ictalurid catfish in ponds is the largest aquaculture sector in the United States. The feed biochemical oxygen demand (FBOD) typically is 1.1-1.2 kg O2/kg feed. Feed also results in a substantial increase of carbon dioxide, ammonia nitrogen, and phosphate to ponds, and this stimulates phytoplankton productivity. Major sources of oxygen in ponds are phytoplankton photosynthesis and mechanical aeration, while major sinks for oxygen are fish respiration, water column respiration (mostly by phytoplankton), and sediment respiration. The dominant processes affecting dissolved oxygen concentration in catfish ponds are phytoplankton photosynthesis and respiration by the entire pond biota. Dissolved oxygen concentrations typically decline when respiration by the biota exceeds phytoplankton photosynthesis. Of course, the most crucial period for low dissolved oxygen concentration is during the night. Mechanical aeration must be applied to ponds to avoid nighttime dissolved oxygen concentrations from falling below the critical level for catfish of 3 mg/L. Floating, electrically-powered, paddlewheel aerators designed specifically for catfish farming are used by nearly all catfish producers. The oxygen-transfer efficiency of these aerators is known, but there is no reliable method for calculating aeration requirement based on stocking and feeding rates in ponds. This results from great variation in phytoplankton abundance among ponds with similar feeding rates and unpredictable weather conditions and phytoplankton die-offs. Dissolved oxygen concentrations in ponds must be monitored, and when the results of measurements suggest that nighttime dissolved oxygen concentration will be unexceptionally low, tractor-powered emergency aerators must be operated immediately to supplement dedicated aeration.