Food chain plate - Huge schools of small forage fish (herring, sardine, anchovy, menhaden) are in the ocean for a reason: they eat plankton and then other things eat them. Yet we remove millions of TONS of small forage fish for - in my opinion- ridiculous, stupid reasons: animal feed, fertilizer, pet food, industrial oils, and also feed for certain farmed fish- which makes the whole practice of aquaculture of predatory fish pretty darn unsustainable.