Land-based aquaculture is a new and emergent way of producing seafood with minimal direct impacts on the marine environment and provides greater system control for farmers. However, fish filets derived from these systems often have flavors that are not desired by end-consumers, hereafter “off-flavor”, which is largely attributed to the accumulation of geosmin (GSM) in fish tissues (Lindholm-Lehto & Vielma 2019). Research is needed to develop solutions for the avoidance or reduction of off-flavors when fish are grown in recirculating aquaculture systems (RAS). However, conducting these research trials currently requires the use of water-borne GSM which is problematic due to 1) the high cost of scientific-grade geosmin and 2) complications associated with GSM dosing and its interactions with life support systems. A previous study with trout showed that feeding GSM-spiked feeds to trout resulted in consistent GSM uptake in fish tissues and presents a potential tool in off-flavor research studies (Dupre et al., 2023); however, this approach has not been validated in Atlantic salmon (Salmo salar). The objectives of this research were to develop an open method for producing GSM-spiked feeds and validate the use of spiked feeds as a means of obtaining GSM in Atlantic salmon (Salmo salar) tissues.
In this study, we produced experimental feeds with five concentrations (10 ug/kg, 50 ug/kg, 100 ug/kg, 250 ug/kg, and 500 ug/kg) of GSM. Feed concentrations were validated using HiSorb™ GC-MS methods and showed a high correlation between targeted and measured concentrations of GSM in the feed (Linear regression, R2 = 0.96). Benchtop trials were conducted to quantify the losses of GSM when feeds were exposed to water (leaching) and as a result of different methods of storage. In addition, a 4 week feeding trial with salmon, evaluating the relationship between feed and tissue GSM concentrations, was also conducted. The results of the benchtop and feeding trials will be reported and discussed. This research will provide a means to obtain consistent off-flavor compound concentrations in salmon tissues during research trials that aim to mitigate and eliminate these compounds in RAS.