Fishing from a sustainable pool

Since the wild catch of fish has reached its ceiling, expanding aquaculture is the only way to meet future fish demand. In 2030, according to FAO, aquaculture will dominate fish supplies. By then, less than half of the fish consumed is likely to originate from capture fisheries. To meet this challenge, aquaculture will have to expand in terms of species cultured and technologies used. Fish farming systems must become more eco-efficient, providing consumers with healthy, abundant and affordable seafood products with minimal impact on the environment.  

 Red list    Fish is gaining popularity in western countries. Health and convenience aspects are main reasons for this, but year-round fresh supply and attractive pricing also play a role. In the UK for instance, the retail seafood market has shown yearly growth rates of approximately five per cent over the last four years. However, negative publicity has to some extent dented the image. For instance, overfishing has created negative publicity around popular carnivorous fish species. Tuna and cod, but also chunky fish like swordfish, have been put on a red list. Biologists now regard several tuna (sub)species such as the Bluefin as endangered and consumption is discouraged. However, the traffic light is also on red for several aquaculture species. Farmed salmon for instance is increasingly associated with water pollution, damage to coastal habitats, threats to wild salmon stocks by escapes and chemical use – even though input of antibiotics and disinfectants in Norwegian ocean salmon farming has been significantly reduced through improved farming practices. According to Fiskekum, the export organisation for Norwegian fish, the use of antibiotics dropped by a factor of 50 between 1987 and 2002. This figure is even more impressive when taken into consideration that the salmon production capacity during this period rose from 33,000 to 460,000 tonnes! Less positive is the situation in the South-East Asia region where tropical prawn aquaculture is threatening mangrove forests because of deforestation. Poor farming practices in some regions have turned wetlands into chemical wastelands with serious consequences for the local population.

 Substitutes    Apart from the environmental impact of aquaculture, the conversion rate from wild fish into farmed fish is a point of discussion. Scientists have calculated that in order to produce 1 kg of Norwegian salmon, approximately 2.7 kg of feed fish is needed. Although many freshwater species show better conversion ratios – some can live on a vegetarian diet - top predators like farmed cod are even greedier than salmon. The capture of low-value fish for the production of fish meal and heart-healthy oil deprives wild living species of their daily bread. According to the World Wildlife Fund (WWF) aquaculture currently uses up to 50 per cent of all fish meal and 80 per cent of all fish oil in the world. Already a third of wild fish are converted to meal and oil.

The International Fishmeal and Fish Oil Organisation (IFFO) is troubled about the current discussion around the conversion factor for wild fish into farmed fish. At the Norwegian conference ‘Aquavision 2006’, director general Jonathan Shepperd stated that IFFO and its members are committed to the sustainable development of the fish meal and oil industry. IFFO expects that once the supply chain tightens, price increases will drive the search for replacements. One alternative to meet the protein requirement is to replace fish meal partially by land animal and plant sources. Plant oils in turn may for a part substitute precious fish oil. Here the challenge is to retain the valuable omega 3 oils in the final product. A lot of research is being conducted into finding substitutes. At the laboratories of feed producer Nutreco for instance 40 per cent of R&D is aimed at replacing fish meal and fish oil with fish free alternatives.

 Plankton farming    A promising replacement is the production of phytoplankton, better known as algae, that are grown in bioreactors near the fishery. Experiments have shown that these unicellular organisms, that contain essential fatty acids for the development of a fishy taste, can be fed to fish in their early life cycle. For some (sub)tropical, omnivorous fish species like tilapia and silver carp, phytoplankton may serve as a complete nutrition source. But algae can also be applied to breed, for example, brine shrimps – part of the menu of carnivorous fishes – and many other zooplankton species. This wide group of tiny organisms that drift in the waters of oceans, seas and freshwater reservoirs, are at the bottom of the seafood chain.

Algae reactors are more than a nutrient plant. They are also a key technology when integrating fish farming and waste management in a closed loop system. Phytoplankton enable farmers to use and treat wastewater at the same time. In an ideal situation algae feed on the waste products of the fishery, create an optimal oxygen/carbon dioxide ratio and are eaten and converted into fish protein at the same time. For reasons of synergy this typically works well when applied to mixed aquaculture systems. These contain different compartments for algae, fish species like tilapia, shellfish and shrimps with different nutrition needs and waste regimes. Although this certainly is a more eco-friendly way to produce seafood, the high costs are an obstacle. Nevertheless, several mixed aquaculture systems have been put in place in Europe and the US. Operations will become more economical in the next years, because the prices of fish meal and fish oil will continue to rise.

Source: MCS Supermarket League Table 2007

 Source: AquaVision Conference 2006