Each year, some 80 million tonnes of wild fish are caught from the world’s oceans. But not all these fish end up on our dinner plates. More than one-third is used to make fishmeal and fish oil. Even this doesn’t all go directly into food or other products: two-thirds goes to make feed for farmed fish.

Aquaculture is one of the fastest-growing food industries in the world as it is in the Western Cape. The growth of the fish farming sector of the industry is largely fuelled by an ever-increasing demand for high-quality fish such as salmon and trout. These are carnivorous fish that in the wild eat smaller fish, squid, and other crustaceans. When farmed, they are fed pellets made largely of fishmeal and fish oil.

Most fish oil and fishmeal is made from small, bony pelagic fish such as anchovies, pilchards, mackeral, herring, and whiting. Some species are also used for human consumption, but others, known as ‘industry fish’, are only used for making these products.

The amount of feed needed for farmed fish is staggering. WWF has calculated that, as a conservative estimate, 4 kilograms of wild-caught fish are needed to produce 1 kilogram of farmed fish. The aquaculture industry currently consumes 70% of the global production of fish oil and 34% of total fishmeal. The salmon and trout fish farming sectors alone consume 53% of the world’s fish oil. And if fish farming continues to grow at the current rate, then by 2010 the aquaculture industry could well be using all of the world’s fish oil and half of its fishmeal.

But small pelagic fish are a finite resource, and many stocks are already fished at — or over — their safe biological limit. A number of fisheries that supply the fish feed industry are located along the coast of Peru and Chile in the southeast Pacific Ocean. In 2001, the United Nations Food and Agriculture Organization (FAO) characterized these fisheries as ‘fully fished’, meaning that they are fished at the maximum safe biological limit. These fish populations also fluctuate under the influence of El Niño events, making them particularly sensitive to overfishing. South American pilchard catches, for example, have decreased drastically from 6.5 million tonnes in 1985 to around 60 000 tonnes in 2001 as a result of El Niño and overfishing.

All this adds up to a feed supply crisis for the fish farming industry.

It will also be hard to increase the percentage of the catch used for fish oil and fishmeal. Peru and Chile have large human populations and for food-security reasons, both governments advocate the use of fish for human consumption. The EU also forbids the catching of some fish for making fish oil or fishmeal.

Collapse of small pelagic fish stocks is not only a problem for fish farms. The fish species used for fishmeal and fish oil are vital for the marine ecosystem. These fish are prey for other fish, birds, and mammals. Heavy exploitation means less food for cod, haddock, and tuna — all commercially important fish — not to mention seabirds such as puffins and marine mammals such as orcas.

The irony is that fish farming is widely viewed — and marketed — as a way to take pressure off wild fish.

There are alternatives to using wild pelagic fish for fish oil and fishmeal. Increased use of offal from fish caught for human consumption is one potential solution that, for the large part, is currently being wasted. Recent years have seen a trend towards processing fish at sea instead of on land. The result is that vast amounts of fish offal are dumped into the ocean. This offal could, however, be used by the fish feed industry. The fish farming industry is also looking at non-fish sources of feed. One alternative is to increase the use of vegetable proteins. There are several examples where fishmeal and fish oil can be substantially replaced by alternative protein and oil sources.

But the alternatives have their own problems. Offal from fish higher up the food chain is often too contaminated by dioxins and other chemicals to be used directly. Cleaning is possible, but would raise the price of the fish oil and fishmeal. Not all farmed fish can be fed a completely vegetarian diet. In addition, the harvesting of another suggested feed alternative, krill, could seriously affect the marine ecosystem because krill is an integral part of the food chain.