Feed accounts for farming of salmonids

Publish date: January 10, 2009

Aquaculture is growing faster than any other means of animal food production in the world. Globally, production has increased by an average of 9.2 per cent per year, against a 1.4 per cent increase in fishing. In 2000 the total production volume in aquaculture was 35.7 million tonnes, compared with 91.3 million from fisheries (FAO, 2002).The UN Food and Agriculture Organization, FAO, predicts that the production volume in aquaculture will increase by 54,000 tonnes each year until 2030.

Today we obtain more than 95 per cent of our food from the soil despite the fact that the primary production of plants in the ocean is almost equally large. The difference is because nearly all food production on land is cultivated, i.e. by means of agriculture or livestock production, at a low level on the food chain. We utilise primary producers, plants and herbivores. At sea, fishing accounts for the bulk of food production, and catches are taken to a large degree from the upper level of the food chain: large carnivores such as cod. At each level of the food chain 90 per cent of the energy is lost. If we can increase utilisation of the ocean’s biomass production by harvesting or cultivating at a lower trophic level of the ocean’s food pyramid, the ocean’s contribution to global food production could be substantially larger than it is today (Åsgård, 2000).

Can salmon be part of such a development? Indeed, salmon is a predator high up on the food chain. Is it right to use fish protein to make fish protein? The claim that "five kilograms of wild fish becomes one kilogram of farmed salmon" has been the main ingredient in the debate as to whether it is a good or poor use of resources to farm carnivorous species of fish like salmon. In this part of the report we will show that farmed salmon is in the process of moving down a step on the food chain. We will see how efficiently salmon farming utilises resources compared with other livestock production, and review some new potential sources of feed. Furthermore, we will describe the management and status of the most important stocks of fish used as feed.

Suitability of feed resources as food for humans
If we wish to maximise access to food in the world, we can move human beings down the food chain. This becomes a thought experiment about the earth’s theoretical potential to feed a growing human population, which quite unrealistically presupposes political supranational control of all market mechanisms. It is nevertheless a supposition attracting a certain amount of interest in the political debate. In raising livestock that are fed "human food", a large share is lost along the way because the farm animal uses energy to move, maintain life functions and body heat, reproduce, etc. The amount of food available to the world’s population would consequently be greater if we turned the feed resources directly into food for humans.

The land used to produce feed for farm animals could to a much greater degree than today be used to produce food for humans. At the same time, the need humans have for protein can largely be met by soya and other lentils instead of meat. The same principles apply to the sea. Forage fish, which to a large degree are used as feed in fish farming, are small and full of bones, but are still nutritionally suitable as food for humans. The species that taste good and are in demand in the various markets are discussed in detail by Strøm (2002).All things considered, the vast majority of fish are suitable food for humans. We can also go lower down the marine food chain and use zooplankton or small crustaceans such as copepods as a source of protein for humans. The demand will hardly make harvesting of such products for food production profitable, but from a nutritional standpoint this resource could conceivably have potential. It is probably more relevant to use these alternatives as a new source of feed for aquaculture – an opportunity discussed later in the section on alternative sources of feed.

Allocation of resources in the market
It is mainly the market – subject to different political operating conditions – that decides how the various food resources are utilised. To increase the share of soya meal used directly as food for humans, the willingness to pay for soya as food must rise so that farmers can achieve higher prices for their crops from food processors than they do from feed producers. The same applies to forage fish. If fishmeal manufacturers receive more money for the meal from, for example, fish cake producers than they do from manufacturers of fish feed, more fish cakes and less feed will be produced. The result of economic development is, however, usually the opposite. Greater prosperity creates higher demand for "exclusive" meat, both from land-based livestock production, fisheries and fish farming (FAO, 2002). On the world market, the richest countries account for the demand for such products. Poor people who would be happy to eat both soya and fishmeal have less purchasing power than the feed industry in the Western world. Should a global food shortage occur that hits more than just the poorest, higher demand for food will yield higher production of food based on what we currently use as feed.

Unless we want to introduce a new economic world order, there is little we can do with the fundamental mechanisms in the market. Through development aid, reduction of various trade barriers and forgiveness of debt, however, the imbalances can be evened out, but this is a completely different debate for which there is no space to discuss here. Theoretically speaking, we can entertain various means to achieve a more "efficient" utilisation of resources. For example, a global prohibition against using fish raw materials as feed for fish or farm animals, would mean a reduction of the demand for this raw material, thereby precipitating a drop in prices. The adjustment of producers (including commercial fishermen) to this new market would in the long term yield a lower production volume. The smaller the demand for the species of fish in question, the smaller the supply on the market will become. If we assume that a prohibition would reduce the production volume to under a third, this would cause a loss of food resources exceeding the loss seen by letting the raw material go through salmon farming, taking into consideration that only 30 per cent of the protein in the feed recurs in the salmon fillet. (See the section "Feed utilisation in salmon compared with other farm animals").

Forage fish are food for other species of fish
So-called forage fish, which are used in the production of fishmeal and fish oil, are also food for other species of fish in the sea – species that are higher up on the food chain. Harvesting of forage fish can thus reduce the availability of food to major species of edible fish, particularly cod. Cod and other species of edible fish are predatory fish in the same way as salmon, and they are found on the same trophic level on the food chain. In theory, we get more out of forage fish when they are taken out of the sea and fed to salmon than when we let them be food for wild cod because feed utilisation is optimised in aquaculture. But such reasoning is too simple. The sea’s ecosystem is complex. You cannot mathematically calculate which species and which level on the food chain will provide the biggest yield, and manage the stocks only by this. Marine biomass production is dependent on a well-functioning interaction between the species and to prevent an imbalance, the harvesting of individual stocks must be viewed from a comprehensive perspective. On land, however, we have accepted complete alternation of the ecosystems. Cultivation of land has displaced wilderness, livestock have displaced wild grazing animals and wild predators have been exterminated to protect livestock. Should we then exterminate the cod to protect more productive species lower down the food chain? Bellona does not think so, and through the Storting’s discussion of Report no. 12 (2001-2002) to the Storting, “Rent and rikt hav” (A Clean and Rich Ocean), the principle of ecosystem-based management of the ocean has been adopted as Norwegian policy (Ministry of the Environment, 2002). Management of fish stocks included in fish feed production is discussed in more detail later in this chapter.

Diet of farmed salmon


The figure to the right provides an overview of the utilisation of feed in salmon, chickens, pigs and sheep (Austreng, 1994). (Sheep sets itself apart in this company because it is a ruminant. Their utilisation of feed is low, but ruminants can live on roughage (fresh or preserved grass), and can consequently utilise resources that are neither suitable for human consumption nor as feed for poultry and pigs. In Norwegian agriculture, a lot of feed concentrate is also used in sheep farming, but we will not go into that here.)

We see from the figure that salmon utilises the energy in the feed twice as efficiently as chickens, and 70 per cent more efficiently than pigs. For protein the ratio is similar: Salmon utilise protein 70 per cent more efficiently than chickens, and twice as efficiently as pigs. Such a comparison between different types of livestock becomes most relevant if they compete for the same sources of feed. Traditionally, salmon have mainly been fed marine raw materials, which in the production of chickens and pigs has only been used in smaller amounts as an appetiser. The positive effect of having a small percentage of fishmeal in chickenfeed means that we can expect continued higher demand for this raw material in agriculture. When farmed fish and terrestrials are increasingly being fed the same raw materials, the comparison of feed utilisation is extremely relevant, and we see that it is more beneficial in salmon farming instead of other types of livestock production.

From raw material to meal and oil
Depending on the type of fish in the raw material, 1,000 kg of fish yields approximately 200 kg of fishmeal, nearly 120 kg of fish oil and 680 kg of water (FAOa).To make 1 kg of fishmeal and 0.5 kg of fish oil you consequently need 5 kg of fish. In theory, from unprocessed fish to processed meal and oil, only the water content disappears. In practice, however, waste can occur due to technical factors. Poor handling of raw material en route from the ocean to the fishmeal factory can reduce the quality to such a degree that it cannot be used as feed. A huge quantity of fish is also lost during the fishing of major species of edible fish. Just in Norway, 140,000 tonnes of fish in the form of fish entrails and the like are thrown overboard from fishing vessels (

Fish and plants – current diet of salmon
Based on the current salmon diet we can estimate how many kilograms of fish are used in producing one kilogram of salmon. The percentage of vegetable raw materials in the feed has as mentioned increased considerably in recent years, and it is not unusual that up to a third of the oil content in salmon feed is vegetable oil and two thirds is fish oil. Feed composition differs greatly over the course of a year, because the price of the raw materials fluctuates widely. Feed manufacturers constantly adjust their output to the market, so that the percentage of marine raw materials can be extremely high at times and low during other periods. We make the following assumptions for the estimate (it is important to bear in mind that these prerequisites are not met in all cases.)

• The feed factor is 1.2 (number of kg of feed/kg of growth)
• 18 per cent fish oil in the feed
• 30 per cent fishmeal in the feed
• 12,2 kg of fish yields 1 kg of fish oil (Skretting)
• 4.39 kg of fish yields 1 kg of fishmeal (IFFO)

(1) 1 kg of salmon x 1.2 kg of feed/kg of salmon = 1.2 kg of feed
(2) 1.2 kg of feed x 0.18 kg of fish oil/kg of feed = 0.216 kg of fish oil
(3) 0,216 kg of fish oil x 12,2 kg of fish/kg of fish oil = 2.64 kg of fish

Production of 1 kg of salmon with 18% fish oil in the feed thus requires oil from 2.64 kg of fish.

It is normal that fish feed contains approximately 35 per cent fishmeal (Waagbø et al., 2001). The equation for fishmeal is thus as follows:

(4) 1.2 kg of feed x 0.30 kg of fishmeal/kg of feed = 0.36 kg of fishmeal
(5) 0.36 kg of fishmeal x 4.39 kg of fish/kg of fishmeal = 1,58 kg of fish.

Production of 1 kg of salmon with 30% fish meal requires meal from 1,58 kg of wild fish.

(6) Surplus of fish meal 2.64 kg – 1,58 = 1,06 kg wild fish

(7) 1,06 kg / 4,39 = 0,24 kg fishmeal

2,64 kg of wild fish is provides enough fish oil and fish meal to produce 1 kg of farmed salmon. In addition it provides a surplus of fish meal of 024 kg.