[bjelkeman-again]

Thanks for the links. EPA and DHA being the key components, the following is often missed when discussing omega-3 fats. So fish fed on vegetable based feed don’t get the EPA and DHA.

“DHA and EPA are present in fish, fish oils, and krill oils, but they are originally synthesized by microalgae, not by the fish. When fish consume phytoplankton that consumed microalgae, they accumulate the omega-3s in their tissues [3].“

[adrian_b]

Earlier, most fish from cultures contained negligible DHA and EPA, because they were not fed with their natural food.

Now, there are fish farms that have cultures of algae that produce DHA and EPA, then they feed crustaceans or rotifers with the algae. The crustaceans or rotifers are added to the fish food, so in such farms the fish contain omega-3, like those grown in natural conditions.

This is not done necessarily to improve the nutritional value of the fish, but to ensure that they reproduce for the next farming cycle, because fish deficient in omega-3 acids may fail to reproduce.