Fish from fish farming feed on fish caught in the sea, so as the number of nurseries increases, catches of sardines and herring have also grown.
According to a study published in the U.S., in 2001, to obtain a kilo of farm fish it was necessary to fish 1.36 kilos of fish. In total, 12 million tons of fish were used to feed the nurseries, an amount that is growing. The problem is due, logically, to the growth of carnivorous fish. Therefore, one of the solutions consists of the cultivation of herbivorous fish.