Several companies are selling krill oil supplements as a source of omega-3s. Krill are shrimp-like crustaceans that are a crucial link in the marine food chain, and concerns about the ecological impact of increased krill fishing has resulted in a ban on this practice on the U.S. West Coast, and strict limits in Norway and Antarctica. In contrast, fish oil supplements are predominantly produced from sardines and anchovies—species that are currently in abundant supply, fished well below mandated limits, and considered ideal for sustainability, given their short reproductive cycles. Fish oil is not only a more sustainable source for omega-3 supplements, it also provides a higher concentration of omega-3, is more molecularly stable, and is backed by more science than krill oil. Fish oil—when manufactured according to international quality standards—has a proven record of efficacy, purity, safety, and sustainability, and is backed by several thousand published studies.