The main ingredients of feeds for farmed carnivorous fish species are fish meal and fish oil, at levels of about 25 percent and 30 percent, respectively, according to Towards Sustainabe Aquaculture in Europe, published by Consensus.

These two ingredients supply essential amino acids and fatty acids required by the fish for normal growth. More recently, small quantities of fish meal and fish oil (3-5 percent and 1-3 percent, respectively) have been included in feeds for omnivorous and herbivorous fish.

Manufactured fish feeds account for 35 percent of the fish meal and 55 percent of the fish oil produced annually. Most of the rest is used in manufactured feeds for terrestrial farm animals and poultry.

Carnivorous fish convert these manufactured feeds to edible flesh with maximum efficiency. Farmed salmon convert approximately 1.2 kg of feed into 1 kg of fish. Poultry convert between 3 and 5 kg of feed into 1 kg of flesh. Pigs convert approximately 8 kg of feed into 1 kg of flesh. Although the introduction of plant protein into the feed can be seen as a way of reducing the sector’s dependence on fish meal and fish oil, some have questioned the trend because:

• Carnivorous fish do not naturally feed on plants;
• Plant proteins may have anti-nutritional effects on fish;
• There is a maximum level of replacement, after which the texture and eating quality of the fish is compromised;
• Some plant proteins could be derived from GMOs

Do farmed fish contain artificial colouring?

The natural red/orange colour of salmon results from carotenoid pigments, largely astaxanthin in the flesh. Astaxanthin is a potent antioxidant that stimulates the development of healthy fish nervous systems and that enhances the fish’s fertility and growth rate. Wild salmon get these carotenoids from feeding on small crustaceans, such as prawns and shrimp. Astaxanthin does not naturally occur in fish feeds and thus must be added. The astaxanthin which is added to feed is identical to the natural pigment.