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.

DHA

Docosahexaenoic acid (DHA) is an omega-3 fatty acid that is a primary structural component of the human brain, cerebral cortex, skin, and retina.

Docosahexaenoic acid(DHA) is a poly unsaturated fatty acid that belongs to the Omega-3 fatty acids. DHA's structure is a carboxylic acid (-oic acid) with a 22-carbon chain (docosa- is Greek for 22) and six (hexa-) cis double bonds (-en-);[2] with the first double bond located at the third carbon from the omega end.

EPA

Eicosapentaenoic acid (EPA; also icosapentaenoic acid) is an omega-3 fatty acid. In physiological literature, it is given the name 20:5(n-3). It also has the trivial name timnodonic acid. In chemical structure, EPA is a carboxylic acid with a 20-carbon chain and five cis double bonds; the first double bond is located at the third carbon from the omega end. Eicosapentaenoic acid can also be formed from alpha linolenic acid, but this conversion does not seem optimal. It is the precursor of important physiological substances in the body, the series 3 eicosanoids: prostaglandins, leukotrienes and thromboxanes

The European and American Food Safety Authorities have approved Health claims for EPA with DHA for Heart Health and DHA for Brain and Eye Health.