What's in fish feed?

One of today's most popular sources of protein is seafood. The demand is constantly increasing and as a consequence almost half of the seafood we eat comes from aquaculture. In fact seafood farming is the fastest growing food production system in the world. It is expected to exceed the production of beef, pork or poultry within the next decades. Aquaculture is also portrait as a method to harvest seafood without further impact on biodiversity probably even reducing the pressure on natural populations. However, the industry heavily depends on marine captured fishes as main nutrient source, e.g. fishmeal.

Fishmeal is a commercial product made from both the whole fishes and their bones and offal from processed fish in order to provide the farmed fish species with natural high quality proteins. The fishmeal industry relies greatly on a “hunting-and-gathering” technique. Cooking, pressing, drying and grinding the fish make fishmeal. As a result, about one-fourth of the seafood harvested from the wild is consumed in fishmeal or other products, not for human consumption. It seems to be a global trend to produce fishmeal using fish processing waste; for example, in Spain and in United Kingdom accounted for 100 and 84% of total fishmeal production respectively. Currently about 25% of the world's fishmeal is generated from fish processing wastes. The proportion is expected to increase, given the growth of aquaculture.

The future expansion of aquaculture may be constrained by the dependence on such low value/trash fish and the impact on natural populations of fish. Therefore, it is very important to have tools in place to monitor fishmeal composition. Obviously, DNA Barcoding lends itself to such investigations but the product in question has been heavily processed which would exclude a conventional Sanger-based sequencing approach.

This is why a group of Egyptian researchers used the metabarcoding approach, applying the Roche/454 platform, to determine fish species composition of fish feeds used in local aquaculture. Their results are concerning as about 46% of all fish species detected are either overexploited or populations are in strong decline. In addition all products contained iridescent shark (Pangasianodon hypophthalmus), an endangered species. 

Interestingly, there are fishmeal products that are incorporated into the diet of herbivorous fishes such as tilapia and carp. The study shows that these products differ in species composition from the those used in fish feed for carnivorous species. However, my first question would be why we are feeding fishmeal to herbivorous species in the first place?

In this scenario, an aquaculture regulatory framework in the countries concerned with fish feed production and trading, including Egypt, should be established in order to regulate fisheries and aquaculture sustainability and to protect biodiversity. Finally, we strongly recommend the introduction of NGS technologies as a tool for fish feed inspections in order to balance/regulate the fish feed productions for sustaining both animal and human life.