Aquaculture is the animal production sector that has experimented the greatest growth rate in the last few years, with an annual increase of 8% between 1970 and2006. Aquaculture contributes with more than 45% to all the fish and seafood consumed worldwide.

Fishmeal as feed

The increase of the aquaculture production has provoked a simultaneously increased of the amount of feed required for aquaculture production, where fishmeal plays and important role.

Fishmeal is a highly nutritional food, due to the protein bioavailability and its high content of minerals and vitamins.

• Manufacturing process and nutritional value

Fishmeal is considered a product obtained from grinding and desiccation of whole fishes, parts of them or from canning industry by-products. Pelagic species are most used.

The normal manufacturing process starts with the chop or grounding of fish, followed by cooking at 100ᵒC for 20 minutes. After that, the product is pressed and centrifuged to extract part of the oil. During the process, a soluble fraction is obtained that can be marketed independently (fish soluble) or reincorporated to the meal. The last step is the desiccation of the fishmeal to a maximum of 10% of humidity. In the first states of the process, an antioxidant is added to avoid fat thickening and combustion.

The nutritional value of the meal depends on the type of fish. The herring fishmeal has a greater protein content (72 vs. 65% -average-) and a lower ash content (10 vs. 16-20%) than the South American fishmeal or the whitefish fishmeal. This latter has a lower fat content (5 vs. 9%) than the other two types.

On the other hand, the freshness, temperature, and stocking conditions affect the deterioration caused by bacterial, enzymatic or rancidity factors and, as a consequence, they affect the peroxide the content of peroxides, volatile nitrogen (TVN) and toxic biogenic amines. Also, high temperatures and extended drying periods decrease the availability of aminoacids by the formation of Maillard products. The manufacturing process has an important effect on its nutritional value.

The most valuable nutritional compound of fishmeal is protein. It has an ideal proportion of highly digestive essential aminoacids, which hardly varies depending on the fishmeal origin. It is considered a good source of protein, lysine and methionine. Also, it has a high quantity of available phosphorous, microminerals (Se, Zn, Cu, Fe and Zn) and group B vitamins (choline, biotin, riboflavin and B12), as well as omega3, eicopentanoic (EPA) and docosahexanoic (DHA) acids.

• Problematic

The use of fishmeal for aquaculture has significantly increased in the last decades. The use of fishmeal as the main feed source in aquaculture entails two problems.

On one hand, the increasing demand of fishmeal can lead to an overexploitation of the natural resources. Half of the fishing resources are fully exploited and the 37% are overexploited already.

On the other hand, from an ethical point of view, the exploitation of the aquatic resources their use as raw materials to produce fishmeal to feed fishes raised in captivity may generate controversy, since those aquatic resources could be used directly for human food.

• Conclusion

Fishmeal constitutes an essential element in feeding of the different cultured fish species due to its high nutritional value and its low cost.

The huge growth of aquaculture has increased the demand of fishmeal can become a long-term environmental problem.

It would be convenient to study different options to replace fishmeal, so that the dependence of the aquaculture industry on this product can be reduced.

* Article updated in 2019 by Dr. Ekaitz Maguregui