Date of Award

Spring 5-10-2025

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Marine Biology

First Committee Advisor

Matt Hawkyard

Second Committee Member

Robert Harrington

Third Committee Member

Gail Schwieterman

Additional Committee Members

Erin Legaki

Abstract

Fish filets produced using land-based Recirculating Aquaculture Systems (RAS) may be prone to containing flavors that are not desired by end-consumers, hereafter “off-flavor”, which is largely attributed to the accumulation of geosmin (GSM) in fish tissues. 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 GSM and 2) complications associated with GSM dosing and its interactions with life support systems. The objectives of this research were to 1) develop an open method for producing GSM-spiked feeds and validate the use of spiked feeds as a means of dosing GSM into Atlantic salmon (Salmo salar) tissues and 2) evaluate the relationship between GSM concentrations measured in blood and various tissues. We produced experimental GSM dosed feeds with five concentrations (10 µg kg-1, 50 µg kg-1, 100 µg kg-1, 250 µg kg-1, and 500 µg kg-1). Benchtop trials were conducted to quantify the losses of GSM between oil and non-oil coated feeds when exposed to water (leaching) and as a result of different methods of storage. In addition, a 3-week feeding trial with salmon, evaluated the relationship between feed and tissue GSM concentrations. The results of the leaching trial showed that non-oil coated feeds had a 3.2% +/- 0.5% loss of GSM compared to the oil coated feed which had 10.4% +/- 0.1% GSM loss. The quantities of GSM measured in feeds following storage was not significant (P = 0.5691) with grand means of treatments feeds 0 µg kg-1, 16 µg kg-1, 52 µg kg-1, 79 µg kg-1, 480 µg kg-1, and 687 µg kg-1, respectively. The results of the 3-week feeding trial showed that increasing concentrations of GSM provided by spiked-feeds linearly correlated with GSM concentrations measured in the muscle tissue (R2 = 0.536), blood (R2 = 0.549), and liver (R2 = 0.441) of Atlantic salmon. In addition, there was a strong linear correlation between blood and muscle tissue GSM concentrations (R2 = 0.892). This research resulted in the establishment of an alternative dosing method for future off-flavor studies focused on Atlantic salmon. It also provides evidence that blood samples may be used as an alternative to tissues, providing a potential non-lethal means of assessing off-flavor in Atlantic salmon.

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