Author
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Torrans, Eugene |
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Submitted to: Aquaculture America Conference
Publication Type: Abstract Only Publication Acceptance Date: 10/6/2004 Publication Date: 1/17/2005 Citation: Torrans, E.L. 2005. Aeration in Channel Catfish Ponds [Abstract]. In: Book of Abstracts. Aquaculture America, January 17-20, 2005, New Orleans, Louisiana. p. 455. Interpretive Summary: Technical Abstract: Aeration is arguably the single greatest factor resulting in the steady increase in catfish production rates seen in the past 40 years. Prior to emergency aeration, feed input was limited to 30-40 lbs/acre/day and production rarely exceeded 1500 lbs/acre/year. Emergency aeration (tractor-powered paddlewheels and pumps) allowed farmers to increase stocking and feeding rates, and production roughly doubled. As production intensity increased to the point that emergency aeration was used in most ponds on a nightly basis, electric aerators permanently installed in the ponds became more economical. A variety of aerators have been developed and used over the years, but the industry has come to rely largely on 10-hp electric paddlewheels for routine aeration, and externally-powered "sidewinders" for emergency aeration. These have proven to be the most economical and reliable for use in large-scale commercial operations. The industry average is near 2-hp/acre, but some commercial farmers are now using up to 6-hp/acre in some ponds. Gross yields exceed 12,000 lbs/acre on some farms. Pond oxygen monitoring systems become more useful at higher aeration rates. Even greater increases in production may be achieved with further increases in aeration; the practicality of this will be determined by economics on a case by case basis. Little research has been done with respect to aerator placement. Catfish fry and fingerlings, much like shrimp, will not move great distances to an aerator during low oxygen events. Farmers typically disperse aeration in those ponds. Since stockers and food fish will move to an aerator, most farmers group multiple aerators together in production ponds. This also allows for a sidewinder to be used in conjunction with the electric aerators to maintain a single 'zone' of aerated water, to which the fish move. Aerators positioned in the middle of the long levee have been shown to be the most efficient at mixing the pond. However, location of power lines, the cost of running extra line and installing additional transformers, the cost of extra gravel for side levees, and convenience of operation usually are determining factors in aerator placement. In commercial ponds with multiple aerators, farmers often turn on the first aerator when the D.O. concentration drops to 5.0 or 4.0 mg/L. While aeration per se is not necessary at that D.O. concentration, the first aerator mixes the pond (in which the D.O. may vary by over 10 mg/L from one end to the other), and establishes a current to which the fish orient. Other aerators are then turned on in sequence as the D.O. falls further. Catfish food consumption, growth and production are largely unaffected until the D.O. concentration falls to below 2.5 mg/L. Liquid oxygen (LOX) has been successfully used in commercial operations to increase oxygen while catfish are being held in a sock. At higher fish production rates, LOX could have potential for routine aeration. Several new aerators are currently being evaluated and will be discussed. |
