DESCRIZIONE
The invention provides systems and methods for producing biofuel from algae that use cultured fish to harvest algae from an algal culture. The methods further comprise gathering the fish, extracting lipids from the fish, and processing the lipids to form biofuel. The multi-trophic systems of the invention comprises at least one enclosure that contains the algae and the fishes, and means for controllably feeding the algae to the fishes. The lipid compositions extracted from the fishes are also encompassed.