The demand for fishmeal and fish oil in aquaculture feeds has increased dramatically in recent years . Alternative protein and oil sources are needed if further development of the aquaculture industry is to be sustained. Terrestrial plant ingredients can replace a portion of the fishmeal used in feeds for a number of species. Complete replacement, however, is seldom achieved . Macroalgae may prove a more appropriate feed ingredient than terrestrial plants products for marine fish feeds as m acroalgae contains many essential nutrients from the marine environment that are limiting in terrestrial plants. Additionally, there appears to be health benefits associated with the use of some macroalgae species for some marine fish species.
Our r ecent studies at NOAA have explored the potential of using domestically cultured macroalgae as ingredients in marine fish feeds. Macroalgae species tested to date include the red macroalgae Pacific d ulse Palmaria mollis and Turkish towel Chondracanthus exasperates , the green macroalgae Ulva spp., and sugar kelp Saccharina latissima. We additionally produced kelp protein concentrates from sugar kelp via chemical and thermal methods and evaluated these ingredients. Using sablefish Anoplopoma fimbria as a model cold water marine species, we evaluated the effects of these novel ingredient on fish growth, feed intake , feed efficiency, whole body nutrient composi tion, liver histomorphology, and gut microbiome . Results will be presented with some species showing positive trends and some species demonstrating negative effects. Of particular interest, t he addition of Turkish towel to sablef ish feeds improved fish liver health and increased fish survival when exposed to the pathogen atypical Aeromonas salmonicida.
Results from our research indicate some macroalgae species may be promising alternative feed ingredients for cold water marine fish . Further research is needed to explore reasons behind observed decreases in feed intake, feed efficiency, and protein retention with some species. Future research directed towards improving the performance of kelp protein concentrates in marine fish feeds and the development of screening methods to identify new promising macroalgae species will be discussed.