Date of Award



© 2022 Gina Scott

Document Type


Degree Name

Professional Science Master's (PSM) In Ocean Food Systems


Marine Science

First Advisor

Zachary Miller-Hope

Second Advisor

Ricardo Ekmay

Third Advisor

Patrick Sirois


With fed aquaculture expanding, challenges are being faced with increasing demands for protein for feed. Fishmeal as a protein is at high cost and low supply, and meals from terrestrial agriculture can impact fish health; both also generate environmental challenges. One potential alternative protein is yeast, which can be grown using waste softwood. Simultaneously, Maine forestry has lost buyers of waste wood with several paper mill closures. If yeast is produced as an alternative protein for fish feed using this wood, both Maine Atlantic salmon farming, Maine’s most valuable form of aquaculture, and Maine forestry could benefit. Environmental impact and stress from the cost and shortage of fishmeal could be reduced or prevented for Maine aquaculture and a new market for waste wood provided for Maine forestry. This thesis was therefore designed to assess if such a concept is reasonable and beneficial considering information from industry stakeholders.

Using feed and protein demand for salmon given by Maine salmon producers and waste softwood availability data from Maine sawmill representatives, as well as literature, it was found that substitution of wood-grown yeast for fishmeal from wild low-trophic level fish and SPC in feed provides benefits to both aquaculture and forestry. A feed formula composed of 5% yeast replacing 29% of fishmeal from wild low-trophic level fish and 15% of soy protein concentrate (SPC) is recommended. When compared to standard feeds, such a feed formula reduces forage fish consumption for fishmeal by 29%, land use for protein production by 10%, and greenhouse gas emissions and acidifying emissions from protein production by 9% each, assuming forage fishmeal and SPC as the major protein components. It also reduces the cost of proteins per metric ton of feed by 8% in such a scenario. Furthermore, there is sufficient waste wood in Maine to feed salmon production using this formula up to the global scale, and even when producing feed containing 5% yeast for only Maine Atlantic salmon aquaculture, wood consumption for yeast production can provide a significant market for waste wood to some sawmills. Although a feed formula incorporating 8% yeast was also tested and found to provide greater environmental and cost reduction benefits for aquaculture, this may exceed feed producers’ expected maximum inclusion levels for ingredients. From perspectives on woodgrown yeast protein among salmon and salmon feed producers and sawmill representatives, several concerns were listed and strategies recommended. Yet there was a generally positive outlook on the proposed protein; thus, quantitative and qualitative data from stakeholders suggests this is a reasonable concept, though much must be considered for it to succeed.


Professional Science Masters Thesis

Advisor Miller-Hope is a UNE faculty member; advisor Ekmay works for Arbiom; advisor Sirois works for Maine Forest Products Council/Maine Sustainable Forestry Initiative.