Assessing the effectiveness of peracetic acid to remediate post-vaccination Saprolegnia spp.-associated mortality in Atlantic salmon Salmo salar parr in recirculation aquaculture systems

Authors: GOOD, CHRIS - Freshwater Institute; DAVIDSON, JOHN - Freshwater Institute; Straus, David - Dave; Wolters, William; Peterson, Brian; PEDERSEN, LARS-FLEMMING - Technical University Of Denmark; PHUNTUMART, VIPAPORN - Bowling Green State University; LEPINE, CHRISTINE - Freshwater Institute; SUMMERFELT, STEVE - Freshwater Institute

Submitted to: International Conference on Recirculating Aquaculture
Publication Type: Abstract Only
Publication Acceptance Date: 4/29/2016
Publication Date: 8/19/2016
Citation: Good, C., Davidson, J., Straus, D.L., Wolters, W.R., Peterson, B.C., Pedersen, L., Phuntumart, V., Lepine, C., Summerfelt, S. 2016. Assessing the effectiveness of peracetic acid to remediate post-vaccination Saprolegnia spp.-associated mortality in Atlantic salmon Salmo salar parr in recirculation aquaculture systems [abstract]. 11th International Conference on Recirculating Aquaculture, August 19-21, 2016, Roanoke, Virginia. 3 p.

Interpretive Summary:

Technical Abstract: Disease is a major barrier to aquaculture production worldwide, and within the salmon industry it is responsible for the majority of market supply fluctuation. Ubiquitous oomycetes of the Saprolegnia genus are particularly problematic disease agents, associated with an estimated 10% mortality among all hatched farmed Atlantic salmon. A major risk period for saprolegniasis is during the weeks following vaccination, the associated stress and tissue damage of which favors the opportunistic Saprolegnia spp. to establish infection and cause clinical disease. Atlantic salmon smolt production is increasingly being carried out in recirculation aquaculture systems (RAS), and therefore effective therapeutic strategies must be developed, not only to reduce losses to saprolegniasis, but also to maintain adequate water quality for fish health and performance, i.e. to not impact RAS biofiltration capacity. There is a clear need to develop novel strategies for saprolegniasis control that are both efficacious and not detrimental to RAS biofilter performance. As such, we are aiming to assess daily low-dose peracetic acid (PAA) treatment regimens to determine their effectiveness in reducing post-vaccination losses to Saprolegnia spp. infections while assessing biofilter performance. Twelve replicated RAS (12 x 0.5m3 circular tanks), each with an associated small fluidized sand biofilter, will each contain 200 Atlantic salmon parr (approximately 40g). A portion (600) of these fish will be PIT-tagged to identify family group; these fish will be in the control tanks, in an effort to estimate heritability of saprolegniasis resistance. The fish will be acclimated for one week following arrival, at which point they will be anesthetized (75 mg/l MS-222) and vaccinated with a commercially available salmon vaccine (furunculosis and vibriosis) via intracoelomic injection following standard industry protocols. Following vaccination, the twelve RAS will be randomly assigned to four treatment groups (n=3), receiving either daily single-dose treatments with i) 0.3 mg/L PAA; ii) 0.9 mg/L PAA; iii) 1.5 mg/L PAA; or iv) no treatment. During the three-week post-vaccination period, daily mortalities will be quantified (with mortalities from control tanks recorded for PIT tag information) and assessed for saprolegniasis via wet-mount microscopy. Survival curves for each treatment will be developed and compared statistically. Thrice weekly water quality samples will be collected and assessed for TAN and NO2-N to monitor biofilter performance. Twice weekly water samples will be collected and assessed for Saprolegnia spp. counts and oomycete genetic sequencing. Pre-study and weekly samples of three fish per RAS will be euthanized (200mg/L MS-222) and gill tissue will be collected for histopathology in order to assess fish welfare under the treatment conditions. Data collection will be completed by mid-May, 2016, and results will be presented at ICRA in August, 2016.