Exploring the Potential of Microalgae as Feed Ingredients for Sustainable Aquaculture: A Review of Nutritional and Environmental Benefits

The increase and rapid population growth and higher demand for fish are driving the aquaculture industry to rapid expansion. One of the main challenges in aquaculture is to ensure sustainable feeds for fish in different aquaculture systems. Historically, aquafeed ingredients were fishmeal and fish oil, but the increase in price and the decrease in availability have resulted in the utilization of some plant-based aquafeed. One of the most utilized plant-based aquafeed and alternative protein sources is soybean meal (SBM). However, the use of aquafeed high in plant protein affects the growth performance, and the production of SBMs requires arable land and freshwater that could be used for crops for human consumption. The substitute aquafeed must possess valuable content, including protein with essential amino acids and lipids with omega 3 fatty acids, and must be palatable and digestible, and it should have low levels of insoluble carbohydrates, fiber, and heavy metals, as these factors can impact fish growth and health. Focusing on microalgae as sustainable alternative has gained interest because microalgae naturally exist in aquatic food chains, with appropriate biochemical composition that could be suitable for lipid substitute in feed as well as fish oil, rich in proteins, carbohydrates, pigments, and other antioxidants. Microalgae, with this balanced composition and high biomass productivity, are considered as a potential aquafeed that can replace conventional ingredients. In this review, we describe how microalgae inclusion in aquafeed or as alternative to conventional sources is conduct to improve sustainability and quality of aquafeeds.