|Dees, P - DILLARD & CO., INC.|
Submitted to: Aquaculture
Publication Type: Abstract Only
Publication Acceptance Date: August 29, 2006
Publication Date: February 26, 2007
Citation: Torrans, E.L., Dees, P.D. 2007. Aerator Placement Strategies [Abstract]. In: Book of Abstracts. Aquaculture America, February 26 – March 3, 2007, San Antonio, Texas. p. 923. Technical Abstract: The purpose of this study was to determine the effects on fish production, water quality and economics of concentrating paddlewheel aeration in large commercial ponds, compared to the current method of aerator placement. Ten 17-acre ponds (approximately 600 X 1300 ft) were brought into the study in pairs as they were stocked for the 2004 growing season. Each pair was stocked near the same date with a similar number of graded stocker catfish. One pond of each pair was a test pond, aerated with the new aerator placement, and the other was a control, aerated using the current (old) system. Three 10-hp electric paddlewheel aerators in the test ponds (new aerator placement) were positioned on three levees near one end of the pond to create a circulation pattern in approximately 25% of the pond area; the three aerators in the control ponds were spaced out on the narrow end of the pond. Dissolved oxygen (DO) concentration was measured at approximately two hour intervals nightly during the growing season. The aerators were operated sequentially according to the farm’s normal practices; turned on when the DO concentration fell to approximately 4.5 ppm, 3.5 ppm and 2.5 ppm, and turned off in reverse order. Aerators were connected to individual hour meters and operation times were recorded at approximate weekly intervals. Additional PTO-powered aerators were used as necessary and run times recorded. Fish in all ponds were fed according to normal farm practices. Individual ponds were “clean harvested” by multiple seining as soon as the fish reached market size (normally longer than one calendar year) and were on-flavor. Water samples were collected at bi-weekly intervals and determinations made for pH, temperature, total ammonia nitrogen, unionized ammonia nitrogen, nitrite nitrogen, chlorophyll, suspended solids (total, fixed and volatile), and secchi disc visibility. While no production parameters were statistically different, mean values for all parameters were better for the new aerator placement: the difference in net annual production was +185 lbs/acre/year; total feed fed was +993 lbs/acre for the production cycle; FCR was –0.08; mean low D.O. (during months with a mean water temperature > 25 C) averaged +0.19 mg/L; days per pond that a tractor was used was 19 vs. 24.2. Due to faulty hour meters on the electric aerators, total (electric) aerator usage was recorded for only four ponds (two of each treatment). Ponds using the new aerator placement ran the aerators 1965 hours per pond vs. 2390 hours for the control ponds (14,459 vs. 17,839 kW-hrs).