Submitted to: International Conference on Recirculating Aquaculture
Publication Type: Proceedings
Publication Acceptance Date: 4/7/2010
Publication Date: 8/22/2010
Citation: Wolters, W.R., Burr, G.S., Schrader, K., Summerfelt, S.T. 2010. Weight loss and fillet quality characteristics of Atlantic salmon (Salmo salar) after purging for 5, 10, 15 or 20 days. International Conference on Recirculating Aquaculture. p. 122. Interpretive Summary:
Technical Abstract: Atlantic salmon, Salmo salar, are typically cultured in marine net pens. However, technological advancements in recirculating aquaculture systems have increased the feasibility of culturing Atlantic salmon in land-based systems to alleviate environmental and disease issues limiting sustainability. One problem encountered when fish are harvested from recirculating systems is the presence of off-flavors from the microbial sources. Moving fish from recirculating systems to tanks supplied with clean water for purging has been proposed to reduce or eliminate off-flavors, but the time required for purging and the effect on weight loss and fillet characteristics has not been adequately evaluated. Atlantic salmon (n=108, mean+SE=2.38+0.35 kg) were cultured in tanks equipped with recirculating systems utilizing biological (fluidized sand) filtration, carbon dioxide stripping, supplemental oxygenation and ozonation, and ultraviolet sterilization and supplied with 2.5% makeup salty well water (14-15 ppt salinity) by flow. To begin the depuration study, half of the fish were moved into a clean fiberglass tank supplied with flow through brackish well water (2-3 ppt salinity) and half were kept in the recirculating system. Fish were sampled at 0, 5, 10, 15, and 20 days and feed was withheld from fish over the 20 day period. All fish were measured for body weight at the start of purging, weight at sampling day, fillet fat and color, and water and fillet samples were collected to measure levels of geosmin and 2-methylisoborneol (MIB). There was a significant effect of sampling day, but no effect of whether the fish were held in a purge tank or kept in the recirculating system on weight and fillet characteristics. There was a significant decrease in weight, fillet fat, and fillet yield over 20 days. Fish lost 3.9 to 5.7% of their weight during purging and fillet fat decreased from 6.5 to 5.2%. Fillet yield calculated from total weight at the start of purging decreased from 53.3 to 51.3%, but fillet yields calculated from the carcass weight at slaughter were not significantly affected by purging. Fillet color scores significantly increased over the 20 day period. Fillet and water samples are being evaluated to determine if geosmin and MIB are contributing to off-flavors in salmon from the recirculating system and if there is a change during purging.