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Research Project: Support the Viability and Expansion of Land-Based Closed-Containment Aquaculture

Location: Cool and Cold Water Aquaculture Research

Title: Evaluating the feasibility of feeding RAS-produced Atlantic salmon (Salmo salar) during the depuration process: Effects on fish weight loss and off-flavor remediation

Author
item DAVIDSON, III, JOHN - Freshwater Institute
item Schrader, Kevin
item MAY, TRAVIS - Freshwater Institute
item KNIGHT, ANNA - Freshwater Institute
item Harries, Marcuslene

Submitted to: Journal of Applied Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2023
Publication Date: 9/27/2023
Citation: Davidson, Iii, J., Schrader, K., May, T., Knight, A., Harries, M.D. 2023. Evaluating the feasibility of feeding RAS-produced Atlantic salmon (Salmo salar) during the depuration process: Effects on fish weight loss and off-flavor remediation. Journal of Applied Aquaculture. https://doi.org/10.1080/10454438.2023.2259892.
DOI: https://doi.org/10.1080/10454438.2023.2259892

Interpretive Summary: Feeding is typically discontinued during the pre-harvest depuration process that is used to eliminate earthy, muddy off-flavor from finfish species produced in recirculating aquaculture systems. Feed withholding eliminates waste from the digestive tract for sanitary processing, alleviates fish stress before slaughter, and reduces nutrient excretion; however, salmon lose weight during this process which impacts farmgate revenue. Therefore, a study was carried out to evaluate the feasibility of feeding a low ration during the depuration process. Feed was either offered or withheld from market-size Atlantic salmon stocked in replicated depuration systems over a 6-day period. This research found that more than 90% of the weight loss that occurred in fasted salmon was eliminated by feeding. Additionally, feeding did not inhibit the rate of off-flavor elimination from Atlantic salmon flesh. On the contrary, levels of common off-flavor compounds, geosmin and 2-methyliosoborneol, were significantly lower in fed Atlantic salmon compared to salmon that had been fasted at the end of the study. This research indicates that feeding Atlantic salmon during the depuration process is a feasible option that could improve farmgate revenue depending on the salable product form among other site specific variables.

Technical Abstract: Depuration is a proven pre-harvest procedure that eliminates common off-flavors from Atlantic salmon produced in recirculating aquaculture systems. However, applied research, including results described herein, indicate that depurating salmon lose weight while fasting, which reduces farmgate revenue. Low-ration feeding was therefore evaluated as a simple method to mitigate weight loss while depurating 3–4 kg Atlantic salmon. PIT-tagged salmon were weighed, exposed to concentrated geosmin (GSM) and 2-methylisoborneol (MIB), and stocked in eight pre-disinfected partial reuse systems. Feed was either offered or withheld (n = 4) during part of a 6-day depuration period. Salmon from both treatments rapidly eliminated GSM and MIB, but slightly lower levels remained in fish that were fed (P < .05). Fed and fasted salmon lost 0.3 and 1.1% of their initial body weight, respectively (P < .05). This research indicates that feeding Atlantic salmon during depuration minimizes weight loss without negatively impacting off-flavor elimination rate.