Fish farms like to claim they are sustainable, and that claim usually surrounds the feed they feed their fish. But feed companies and commercial fishers, sometimes fish farm operations themselves, can no longer catch enough forage fish to form fish feed.
Fish farms have fished down these stocks, for example, anchovy and Jack Mackerel off Chile, and currently, anchovy off Peru, that the cost of the fish meal has become too high. So fish farms have made wild fish unsustainable, and increased the price so much that the feed is too expensive to be put in feed. In other words, both ends of fish farming feed are unsustainable.
I should add that substituting soy, has lead to complaints over moving aboriginals off their lands, clear cutting the forest and planting soy. Soy also has GMO issues. And fish feed companies are now using chicken feathers instead of fish where they can. Would you eat chicken feathers? Fish feed sometimes uses land animal feces in their feed. I asked EWOS six times whether they use feces in their feed. No response.
Here is a good article on the sustainability of fish meal in fish feed by Rabobank: http://www.undercurrentnews.com/2015/06/09/fishmeal-will-move-from-being-commodity-to-high-price-strategic-marine-protein/?utm_source=Undercurrent+News+Alerts&utm_campaign=ea63c2bf44-Americas_briefing_Jun_09_2015&utm_medium=email&utm_term=0_feb55e2e23-ea63c2bf44-92426209.
Rabobank says that Peruvian harvest is down, just as I have mentioned: In 2014/15, fishmeal was in short supply due to thecancelation of last year's second Peruvian fishing season, linked to an El Nino weather phenomenon."
The same can be said for jack mackerel and sardines in Chile, and capelin and other small species off Europe itself.
Rabobank ponts out that fish farms are in direct competition with third world countries that want their humans to eat anchovy and other small pelagics:
"The decline in supply has been driven by both lower wild catch of small pelagics and, more importantly, increasing direct human consumption of these species, which is likely to put ongoing pressure on animal and aqua feed producers -- the key competitors for fishmeal."
So, how much do fish feed producers buy? A very large amount of feed that can be sold to humans:
"The aquaculture industry is the main buyer for fish oil globally, consuming some 74% of available supply, primarily for use in salmon feed."
And those Omega 3 fatty acids?
"The salmon industry currently uses approximately 7-9% fish oil in the feed formula. This amount could probably be reduced to 5-6%, but any lower than this could negatively impact the performance of the feed," Rabobank said.
Rabobank further says that the health image of farmed salmon, at least to companies like Marine Harvest, Cermaq (Mitsubishi) and Grieg Seafood, is largely tied to that Omega-3s:
"... omega-3 polyunsaturated fatty acids. Without fish oil, the most known health befits of eating salmon would not be present,"
Fish farms sustainable? I don't think so.