Massive stocks of smaller fish are depleted to feed farmed salmon, and parasites flourish in salmon pens where farmers use pesticides, contributing to pollution and ecosystem destruction. Sea lice have infested farms in Norway and Scotland in recent years, and a deadly algal bloom killed salmon in Chile, a top farmed-salmon producer. Farmed fish sometimes escape, too, contaminating nearby wild salmon.

With rising incomes in developing nations driving demand, fish and seafood now account for almost a fifth of the animal protein people consume. Unsurprisingly, the need for a solution to this less-than-virtuous circle has become evident to a growing number of entrepreneurs and startups.

The move toward environmentally conscious salmon farming is already underway.