Omega-3 fatty acids are polyunsaturated fatty acids (PUFAs). The three types of omega-3 fatty acids involved in human physiology are α-linolenic acid (ALA) (found in plant oils), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) (both commonly found in marine oils). Marine algae and phytoplankton are primary sources of omega-3 fatty acids. Common sources of plant oils containing the omega-3 ALA fatty acid include walnut, edible seeds, clary sage seed oil, algal oil, flaxseed oil, Sacha Inchi oil, Echium oil, and hemp oil, while sources of animal omega-3 EPA and DHA fatty acids include fish, fish oils, eggs from chickens fed EPA and DHA, squid oils, and krill oil.
Sadly large numbers of fish is being caught to be processed to Omega-3 oil and fish meal. Completely unnecessary because we can get the Omega-3 directly from Algae.