USDA-ARS Catfish Genetics Research Unit,USA
Casey C. Grimm from the Southern Regional
Research Centre New Orleans, USA.
This research was executed by Ph.D. Paul V. Zimba from the USDA-ARS Catfish Genetics Research Unit, USA and Casey C. Grimm from the Southern Regional Research Centre New Orleans, USA, utilizing the LG Sonic® ultrasound technology in channel catfish production.
An initial laboratory study evaluated the effect of ultrasound produced by the LG Sonic® technology on catfish feeding and weight gain. Catfish fingerlings stocked at 13 fish tanks were acclimated to four control tanks and four tanks that received ultrasound treatment. Turbidity in tanks was decreased by 60% (Figure 1). Bacterial cell counts using acridine orange direct counts and bacterial plating were significantly lower in the tanks with the ultrasound treatment compared to the counts in control tanks. These results suggested that use of ultrasound could reduce pathogenic bacteria in ponds to levels below those causing fish mortalities.
A further laboratory experiment assessed if ultrasound caused greater off-flavor diffusion from water to air. Eight tanks were dosed with 1-ppm 2-methylisoborneol, and four were treated with continuous ultrasound. Samples were collected daily for off-flavor and analyzed using gas chromatography-mass spectrometry. Tanks with ultrasound treatment had significantly (P = 0.09) lowered off-flavor levels.
A field study was initiated in 0.47-ha production ponds to assess the impacts of ultrasound produced LG Sonic® by technology on off-flavor and algal biomass. Ponds were stocked with channel catfish fingerlings and operated as growout ponds according to industry standards.
Pond conditions were matched in terms of algal density and composition in two control ponds and two ponds treated with ultrasound. Two ultrasound devices were placed in ponds pointing along the long pond axes. The ultrasound equipment was run from 11 a.m. to 6 a.m. continuously, with feeding during the off period. A dense bloom of the cyanobacterium Microcystis c.f. ichthyoblabe Kützing was present in two of the ponds. While dominant in two other ponds, the bacterium was 70% lower in overall biomass. Total algal biomass decreased by about 48% during the four-week study. Off-flavor concentration was decreased to a lesser degree.