An animal feed with a high level of arachidonic acid is produced from microalgae, and fed to aquatic animals grown in aquaculture. The arachidonic acid-rich microalgae are fed directly to the aquatic animals, or processed to produce an oil that can be used as a human nutritive supplement. The arachidonic acid-rich microalgae can be combined with long chain omega-3 fatty acids to provide a source of nutrition for humans and animals. The animal feed and nutritional supplements are free of animal byproducts.