Depleting fish stocks

Most farmed marine fish and shrimp species are carnivorous. They are either fed whole fish (mainly in the case of tuna) or pellets made of, amongst other things, fishmeal and fish oil. In both cases, the fish used as feed are caught from the wild. The amount of feed needed for farmed fish and shrimp is staggering. For example: up to 22kg of wild-caught fish is needed to produce just 1kg of farmed tuna 4kg of wild-caught fish is needed to produce 1kg of farmed salmon up to 2kg of wild-caught