Substitution of fish oil with cheaper vegetable oil in aquaculture feeds may also affect consumer demand, as evidence suggests that the ratio of n-6:n-3 fatty acids in human diets is already too high. There are, however, alternative sources of n-3 fatty acids for humans, including molluscs and other types of seafood, and research is underway to increase the n-3 fatty-acid content in poultry products and in oilseeds used for feed78,79 (W. F. Kirk,
personal communication). A move towards partial substitution of plant and terrestrial animal proteins for fish proteins in feed is widely accepted within the aquaculture industry, but the urgency of such efforts remains controversial. Because over-exploitation of pelagic fisheries has negative ecological and social consequences, developing a strategy to replace fish meal and fish oil in feeds should become both a private and public-sector priority