Fish are an important source of omega-3 fatty acids in human diets but the volume of fish caught in the wild is not keeping pace with the ever increasing demands for fish products.

As a result, aquaculture has become a very important source of fish for human consumption. However, highly valued species such as salmon require large amounts of protein and oil in their diet. Traditionally the primary source for this has been fishmeal and oil from rendered fish caught in the wild but the supply of fishmeal and oil is not adequate to meet demands for this growing industry.

Numerous studies have shown that vegetable oil, including flax oil, can replace fish oil in fish diets without affecting growth performance. The fat composition of fish is a direct reflection of the oil used. Unlike feeding a diet high in saturated fats or omega-6 fats, feeding a diet high in flax oil will result in a meat product that is desirable to consumers. Flax oil can be fed to fish and completely replace the fish oil in the diet. Since the oil is high in omega-3 fatty acids, the fish will retain a desirable fatty acid profile.  

The oil is prone to oxidation so an anti-oxidant should be added to the oil to prevent rancidity. The oil in flaxseed is naturally protected from oxidation so it would seem wise to feed the seed directly to fish. However, the mucilage and fibre negatively affect nutrient absorption in most fish species making it impractical to feed. Researchers at the University of Saskatchewan have studied the potential to use processed flaxseed in the diets of rainbow trout and reported significant improvements in performance when the mucilage was removed by hot water extraction. However, this technology is not yet being applied commercially.

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