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CTA. 2005. Sea Farming. Spore 120. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/48034
Internet URL: http://spore.cta.int/images/stories/pdf/old/spore120.pdf
Marine algae have become essential ingredients for the manufacture of many food products, textiles, cosmetics and other goods...
Marine algae have become essential ingredients for the manufacture of many food products, textiles, cosmetics and other goods. They offer interesting opportunities for ACP coastal communities, some of which have already moved into seaweed farming. Stimulated by strong demand from the manufacturing industry, especially the food and textile sectors, seaweed farming is developing rapidly in coastal communities around the world. While harvests of wild seaweed have remained stable at around 1 million t for the past 30 years, global output of farmed seaweed has increased eightfold in the same period. According to FAO figures, production levels of fresh seaweed had already exceeded 8.5 mt by 2003. And experts predict that this steady growth is set to continue. There are several thousand known species of marine macroalgae, classified according to their green, red or brown colour. But only a few dozen are used, and these are becoming increasingly sought after. Much in demand are the red seaweed varieties Chondrus, Eucheuma, Gelidium and Gracilaria and the brown ones Laminaria and Macrocystis. Brown seaweed (5.6 mt in 2003) is the most commonly farmed type, with production easily outstripping that of red seaweed (2.8 mt) whose output, nevertheless, rose by 75% between 1993 and 2003. By contrast, farming of green seaweed, or sea lettuce, is undergoing a sharp decline, with production down to 7,167 t in 2003, compared with 91,169 t in 1993. Remarkable properties A wide variety of industrial sectors rely on phycocolloids or hydrocolloids seaweed extracts which act as vital thickening, gelling and stabilising agents. Alginic acid, derived from brown seaweed and able to retain up to 140 times its own volume of water, is crucial to the food and textile industries. The gelling properties of agars, extracted from red seaweed, are essential to all sorts of industrial preparations such as jams and sauces. Carrageenans, which are also derived from red seaweed, are mainly used in the manufacture of milk-based desserts. Harmless and low in fat, all of these substances are also increasingly used in the manufacture of health foods. The food and textile sectors alone absorb an average of 80% of global production of these extracts, and demand is continuing to grow. Since the harvesting of wild seaweed can no longer fulfil the demand, a number of coastal countries of the South have ventured into seaweed farming, sometimes encouraged by manufacturers who are keen to secure a reliable source. In Africa and the Pacific Islands, seaweed farms mainly produce Eucheuma algae. Labour intensive, but requiring little investment, seaweed farming is well suited to small-scale production. The technique involves fixing cuttings on lengths of twine stretched between stakes, or on nets. After 6 weeks, the seaweed is ready for harvesting. Dried in the sun, and protected from the sand, it can keep for up to 2 years. The example of Kiribati, the world s 15th biggest producer of red seaweed (3,900 t), shows that seaweed farming could well become a profitable activity for coastal communities in the Pacific, replacing copra, which is running out of momentum. Eucheuma produced in Kiribati is shipped to Norway for treatment. Thanks to the excellent quality of the product they offer, fishers from the atolls who have switched to seaweed farming have been able to command guaranteed prices from the manufacturing industries. Their shift has had a positive effect on fish stocks and the coastal environment. Vanuatu is also seeking to set up seaweed farms, as are Fiji and Tonga. In other ACP regions, South Africa is the only country with a significant output of brown algae (30,000 t), while Tanzania leads the field in terms of red seaweed production (115,000 t), followed by South Africa and Madagascar, with, respectively, 2,000 and 1,700 t. According to FAO, there are also good prospects for countries such as Mozambique, Namibia and Senegal. Coastal ACP countries are currently limited to supplying the raw material. But can they make the transition and begin extracting and marketing these highly sought after marine vegetable derivatives on their own account? According to the experts, extraction would require a level of investment that is beyond the means of most countries of the South. What is more, this is a highly concentrated sector there are only a handful of factories worldwide, and all of them are located in industrialised countries, with the exception of Zanzibar in Tanzania (see Spore 102, page 8). Sea vegetables Farming seaweed as a food product is another avenue worth exploring. Rich in minerals (iodine, calcium) and in vitamins (A, C and E), seaweed have been eaten by Asian communities for centuries. Certain ACP countries such as Namibia and Tonga are starting to farm