World Aquaculture March 2019

WWW.WA S.ORG • WORLD AQUACULTURE • MARCH 2019 55 ( C O N T I N U E D O N P A G E 5 6 ) Straus et al. (2018) determined the toxicity of PAA to 12 species of fish important in aquaculture in 24-h bioassays. The concentration of PAA that is safe for fish ranges from 1.9 mg/L for fathead minnow to 5.9 mg/L for blue tilapia. John Davidson at the Freshwater Institute also joined our group as a collaborator and gave a presentation that asked “Is Continuous Peracetic Acid Dosing in RAS Really as Good as Ozone?” (Davidson et al. 2017). In this research, water quality data from ozone-treated RAS tanks of a previous study were compared to the effects observed when applying semi-continuous treatments of PAA. Results indicated that PAA treatments did no harm to rainbow trout or biofilter performance, but ultimately PAAwas not a viable replacement for ozone. We surmise that the low semi-continuous treatments and resultant constant input of acetic acid, which breaks down to a carbon-source for microorganisms, was not enough of an abrupt change as pointed out by Liu et al. (2017a). Liu et al. (2018) continued his work with RAS to look at parameters affected by treatment with 1 mg/L PAA two times per week for three months. They measured total aerobic bacterial density in the water, plasma cortisol, respiratory burst of kidney leukocytes and observed histology between treated and control fish. Overall, PAA had a beneficial effect on the RAS and the fish. The study of Gesto et al. (2018) followed up on the fish used in the Liu et al. (2017a) study but added a secondary chasing stressor and evaluated the stress-response by measuring plasma cortisol, plasma glucose, plasma lactate and brain serotonergic activity. Results suggest that fish truly habituated to PAA, supporting the recommendation that PAA is a welfare-friendly disinfectant. The most recent publication from our collaboration (Davidson et al. 2019) was a thorough analysis of water quality and fish performance data presented previously (Davidson et al. 2017). Rainbow trout performance metrics were not affected by PAA dosing and water quality was generally unaffected for most tested parameters. An interesting finding was that oxidation reduction potential can be used to potentially monitor for PAA residuals. In summary, our collaborations have contributed greatly to the potential expansion of the use of PAA in international aquaculture. A comprehensive review of the use of PAA is being compiled and we plan to make this available soon. Notes Dave Straus – U.S. Department of Agriculture - Agricultural Research Service, Harry K. Dupree - Stuttgart National Aquaculture Research Center, Stuttgart, Arkansas 72160 * Corresponding Author: Dave.Straus@ars.usda.gov Thomas Meinelt and Dibo Liu - Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany. Lars-Flemming Pedersen - Section for Aquaculture, North Sea Science Park, DTUAqua, Technical University of Denmark, Hirtshals, Denmark. Chris Good and John Davidson - The Conservation Fund’s Freshwater Institute, Shepherdstown, West Virginia 25443 Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the Leibniz-Institute of Freshwater Ecology and Inland Fisheries or the U.S. Department of Agriculture. Postscript: The authors have enjoyed the experience of recalling activities of their collaboration and encourage others to share their experiences with long-term research collaborations in World Aquaculture . References Davidson, J., C. Good, D. Straus, K. Schrader and S. Summerfelt. 2017. Is continuous peracetic acid dosing in RAS really as good as ozone? Aquaculture InnovationWorkshop, Vancouver, British Columbia. Davidson, J., S. Summerfelt, D.L. Straus, K.K. Schrader and C. Good. 2019. Evaluating the effects of prolonged peracetic acid dosing on water quality and rainbow trout Oncorhynchus mykiss performance in recirculation aquaculture systems. Aquacultural Engineering 84:117-127. Farmer, B.D., D.L. Straus, B.H. Beck, A.J. Mitchell, D.W. Freeman and T. Meinelt. 2013. Effectiveness of copper sulphate, potassium permanganate, and peracetic acid to reduce mortality and infestation of Ichthyobodo necator in channel catfish Ictalurus punctatus (Rafinesque 1818). Aquaculture Research 44(7):1103- 1109. Troughs used in experiment on controlling catfish egg fungus with peracetic acid (Photo: Cindy Ledbetter). Pellet tank (1000 L tote) of peracetic acid used at a Danish Trout farm (Photo: Lars-Fleming Pedersen).