Chia seeds

Chia seed oil contains about 64% omega -3 fatty acids.

An excerpt from the article 16 facts about chia seeds

It also contains omega-6 fatty acids, which occur in a beneficial ratio to omega-3 for health and disease prevention. It has more omega-3 fatty acids than Norwegian salmon, considered the richest source.

Chia seeds are the best-known plant source of omega-3 fatty acids, better than flax seeds.