Title : Can we farm eelgrass as a high protein sustainable marine grain for aquaculture?
Abstract:
In 2001, the Food and Agriculture Organization (FAO) predicted that aquaculture-raised seafood would surpass fish-natural stock catches in 2030 (Aquaculture News, Vol. 9, No. 3, January, 2001). The aquaculture industry did not need to wait until then. Aquaculture seafood surpassed capture fisheries in 2022. With a growing world population, the need for sustainable food places increased production from diverse culture feeds that are responsive to best practices and lessen anthropogenic impacts. A limiting factor continues to be sustainable high protein feed ingredients. A recent FAO report (2024) “The State of World Fisheries and Aquaculture” mentions the need of lower trophic food webs and alternate protein sources as key to maintaining and expanding worldwide aquaculture production.
Novel protein sources, once overlooked, are being re-examined as future potential feed ingredients. For three decades, concerns have been mentioned about high trophic impacts to forage species as primary feed ingredients (Fishing Down Marine Food Webs, Natural Science, Vol. 1997). One possible source of high protein grain could be from the eelgrass plant, Zostera marina. Eelgrass has a history of human food use (Felger et al., 1973, Science, Vol. 181, July 27, pp. 355-356) as mentioned in a New York TimesTM article on July 28, 1973 “Remote Indian Tribe in Mexico Eats a Grain in the Sea” by Walter Sullivan, pg. 24. Studies conducted on protein content found that Zostera grain was in the range of wild rice, wheat and rye grain, about 13% protein (Perez-liorens et al., “Sea Rice,” December, 2023).
Unfortunately, only a few papers describe the soil conditions for eelgrass growth or its ability to produce a high protein grain. Soil science studies are noticeably absent in the marine soil literature as compared to terrestrial grain soil research. Controlled eelgrass farming may remove nitrogen compounds (identified as damaging in many coastal areas) and provide habitat nursery services to natural fisheries as well as a potential future source of plant-based protein. To my knowledge, no current feed trials utilizing eelgrass grain for prepared feed ingredients are underway while some research is concentrating on alternate sources of unsaturated fats and essential amino acids for formulated fish feed.
Eelgrass (Zostera marina) is a highly efficient C-3 plant that requires no fertilizer and parent root stock may live a decade or longer. Some reports from northern Europe in areas where eelgrass wrack is considered a nuisance indicate that eelgrass monocultures can exist in the same general habitat for three centuries or longer.
A barrier to aquaculture trials is the result of most of the harvested seeds being used in restoration projects. It is a time-consuming process for hand harvests, and seed planting is often made in poor or unsuitable marine soils. Terrestrial culture technology and related soil science may help evaluate if eelgrass grain is a sustainable protein ingredient for aquaculture feeds.
