Seafood: Environmental Impacts

salmon

Salmon as an Example

Salmon are carnivorous.  Farmed salmon are often fed fish meal, or ground up parts of other fish.  In certain countries (France for one), it is considered more desirable to eat salmon that are fed a diet closely mimicking what they would eat in the wild. In places like Scotland that supply farmed fish to those countries, the salmon are fed 100 percent fish meal. Though feeding the salmon a diet that closely mimics their natural diet may seem in greater harmony with nature, trying to do this for a large number of fish raised in a captivity requires catching large quantities of other fish species—resulting in large CO2 emissions from the fishing boats and transportation of fish meal to the farms.  Raising salmon in Scottish fish farms, in fact, produces 3,300 kilograms of CO2 per ton of fish.

By contrast, farm-raised salmon in Norway produce a little more than half of that total-- 1,750 kilograms of CO2 per ton of fish.  That is because Norway mixes in large amounts of grains to the feed, which provides the necessary nutrition but produces much less carbon.1  Not only does it reduce emissions, it has the added benefit of reducing the burden on the smaller bait fish, which gives the wild populations of salmon more food to thrive on.

Carbon dioxide emissions are not the only problem with aquaculture.  Waste is another. Scotland's salmon aquaculture industry, for example, is estimated to produce the same amount of nitrogen waste as the untreated sewage of 3.2 million people--just over half the country's population.3 

Salmon farming is by no means the only potentially destructive form of aquaculture. Learn more about shrimp farming’s negative impact on the environment.