Consumption Dysfunction
More and more health studies are claiming that the protein and omega-3‚ found in seafood are beneficial to people‚ health, while other studies indicate that health problems are a result of high red meat consumption. At the same time, seafood marketing has escalated and consumers are inundated with seafood advertisements. As a result, there is increased demand for high-value seafood, and the aquaculture industry envisions this as an opportunity for rapid growth.
Aquaculture proponents claim that wild fish populations are overfished and the only way to meet consumer demands is through aquaculture. The situation is not this cut and dry. Farm-raised fish require at least 3 pounds of wild fish for each pound of farm raised fish. More fish are removed from the oceans to feed farm raised fish, thus not alleviating stressed wild fish populations. According to the United Nations Food and Agriculture Organization, 75% of the world‚ wild fish populations are approaching an overfished condition, overfished or depleted.
The small fish used for fish feed are food for bigger fish, such as cod. Removing small fish from the oceans for aquaculture will only exacerbate the problems. Policies must be developed to rebuild the stressed populations and enhance those that are flourishing.
As aquaculture is increasing worldwide, the production of fish feed is one of the fastest growing industries in the world, expanding by more than 30% per year.1 Within the next 10 years, it is estimated that demand for fish feed will increase by 300%.2 However, the supply of fishmeal and fish oil remains stagnant and unreliable. Therefore, in order to meet the increasing demand, aquaculture proponents are investigating the use of alternative sources of protein, especially soybean meal.
It is important to consider the nutritional value of these protein replacements. Fish feed must contain not only nutrients sufficient to produce growth, but also to meet the needs of immune systems to fight off disease.3 Finfish aquaculture is unsustainable, and partial adjustments to fish diets will not change this fact.
Fishmeal: A Limited Resource
Wild fishmeal is the main protein source for farmed fish because of its balanced amino acids and high digestibility. In 2004, 24% of the wild fish catch (32.2 million tons) was used for non-food products, primarily for fishmeal and oil.4 Typical ingredients include small fish, such as anchovies, jack mackerel, pilchard, menhaden, herring and sardines. Chile and Peru are the major producers of fishmeal, exporting two-thirds of the fishmeal on the world market. This geographic concentration of production makes the supply unreliable, vulnerable to natural changes, and subject to price instability. In 1998, for example, El Niño caused a significant decrease in production and a dramatic increase in price.
As an alternative, some aquaculture proponents endorse using seafood processing waste. Along with this waste, large quantities of bycatch are seen as possible alternatives. Using waste and bycatch, however, would further deplete wild fish populations. The better alternative is developing gears that will decrease the amount of bycatch in the first place. Additionally, the global supply of fishmeal is limited and will likely be unable to meet the needs of the growing aquaculture industry.5
Soy: A Viable Alternative?
The partial replacement of fishmeal with soybean meal (SBM) is currently the most appealing.
Adding it to fish feed could lower costs by one-third to one-half.6 Also, soy is more plentiful and grows four times faster than fishmeal. However, soybean meal is not as rich in amino acids as fishmeal.7 Soybean meal also has several anti-nutritional factors. Fish can only tolerate a certain percentage of soy before health problems ensue, including decreased growth rate and depressed immuno-capacity.8 Different species of fish react differently to soy. While some carnivorous fish can tolerate 20% SBM replacement, most fish can handle only 10-15%.9
Alternative Alternatives?
Other protein sources are being investigated as possible replacements for fishmeal in fish feed , including animal proteins, peas and grain proteins.
Poultry by-products, meat, bone and blood meal are low-cost and are in rich amino acids. Up to 25% of fishmeal can be replaced with meat and bone meal, but higher levels will significantly stunt growth. Also, the digestibility and nutritional value of these products are highly variable. It is unlikely that animal proteins will be widely used in fish feed, because they are being fully utilized by the agricultural industry for animal feed and pet food.10
Peas contain anti-nutritional factors such as fiber, posing a similar problem as soy. Peas can be processed to produce protein concentrate, which is more digestible, but this is likely to increase cost. Wheat gluten can replace up to 25% fishmeal. Wheat gluten, however, is rather expensive. Corn gluten, which can replace 25-40% of fishmeal, costs less. It can turn some fish fillets yellow, however, making it less desirable.11
Conclusion
Despite extensive scientific experimentation, no suitable alternative to wild fish has been found for fishmeal in the diets of carnivorous finfish. There simply are too many components of soybeans that interfere with nutrient digestion in fish. These anti-nutritional factors not only reduce fish growth, they also decrease the nutritional value of seafood for the consumer. Other possible protein substitutes have turned out to be in short supply, impractical, or to cause nutritional problems similar to the soybean meal. And, because scientists have been unable to replace more than 40% of fishmeal, wild fish will continue to be relied upon to feed farmed fish.
Footnotes
1 A.G. J. Tacon, ‚Aquafeeds and Feeding Strategies.” In: ‚Review of the state of world aquaculture.” FAO Fisheries Circular. No. 886, Rev. 1. FAO Inland Water Resources and Aquaculture Service, Fisheries Resources Division. (Rome: Food and Agriculture Organization of the United Nations, 1997)
2 Saskatchewan Agriculture. ‚Farmers could profit from fish food demand,” The Western Producer. (1 Feb 2004)
3 Tacon. ‚Feeding.” p. 26
4 UN FAO. ‚The State of the World fisheries and Aquculture 2004″ FAO Fisheries Department, Rome 2004. p. 6.
5 Tacon. ‚Feeding.” p. 16
6 Daniel J. Grant. ‚Aquaculture industry expected to increase use of soybeans for feed,” Agrinews. (27 February 2004)
7 Lourens de Wet. ‚Use of soya in aquafeeds.” Presented at Annual Symposium of Animal Feed Manufacturer‚ Association. (13 August 2004) p. 10
8 de Wet. p. 11
9 Soybean Meal Info center. ‚Soybean Meal in Aquaculture.”
10 Ronald W. Hardy. ‚New developments in aquatic feed ingredients, and potential of enzyme supplements,” Avances en Nutrición Acuícola V. Memorias del V Simposium Internacional de Nutrición Acuícola. 19-22 Noviembre, 2000. L.E. Cruz-Suárez, D. Ricque-Marie, M. Tapia-Salazar, M..A. Olvera-Novoa, y R. Civera-Cerecedo, eds. (Mérida, Yucatán, México, 2000.) p. 220
11 Hardy. p. 222