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Seaweeds have a long history of use as food, as flavouring agents, and find use in traditional folk medicine. Seaweed products range from food, feed, and dietary supplements to pharmaceuticals, and from bioenergy intermediates to materials. At present, 98% of the seaweed required by the seaweed industry is provided by five genera and only ten species. The two brown kelp seaweeds Laminaria digitata, a native Irish species, and Macrocystis pyrifera, a native New Zealand species, are not included in these eleven species, although they have been used as dietary supplements and as animal and fish feed. The properties associated with the polysaccharides and proteins from these two species have resulted in increased interest in them, enabling their use as functional foods. Improvements and optimisations in aquaculture methods and bioproduct extractions are essential to realise the commercial potential of these seaweeds. Recent advances in optimising these processes are outlined in this review, as well as potential future applications of L. digitata and, to a greater extent, M. pyrifera which, to date, has been predominately only wild-harvested. These include bio-refinery processing to produce ingredients for nutricosmetics, functional foods, cosmeceuticals, and bioplastics. Areas that currently limit the commercial potential of these two species are highlighted. 

This volume addresses the potential for combining large-scale marine aquaculture of macroalgae, molluscs, crustaceans, and finfish, with offshore structures, primarily those associated with energy production, such as wind turbines and oil-drilling platforms. The volume offers a comprehensive overview and includes chapters on policy, science, engineering, and economic aspects to make this concept a reality. The compilation of chapters authored by internationally recognized researchers across the globe addresses the theoretical and practical aspects of multi-use, and presents case studies of research, development, and demonstration-scale installations in the US and EU.

4.1 Historical Perspective

Aquaculture has a tradition of about 4 000 years. It began in China, possibly due to the desires of an emperor to have a constant supply of fish. It is speculated that the techniques for keeping fish in ponds originated in China with fishermen who kept their surplus catch alive temporarily in baskets submerged in rivers or small bodies of water created by damming one side of a river bed. Another possibility is that aquaculture developed from ancient practices for trapping fish, with the operations steadily improving from trapping-holding to trapping-holding-growing, and finally into complete husbandry practices (Ling, 1977).

Table 5. Possible environmental Impacts of aquaculture

Source: Modified from Pullin, 1989

Chinese who emigrated to other Southeast Asian countries probably carried the knowledge with them and inspired the local people to take up fish farming. Brackishwater aquaculture is thought to have originated in Indonesia with the culture of milkfish and grey mullet (Ling, 1977) and must have spread to neighbouring countries like the Philippines which has been practising it for about 300 to 400 years (Baluyut, 1989).

The husbandry of fish is therefore not a new phenomenon. Ancient practices based on the modifications of natural bodies of water or wetlands to entrap young fish in enclosures until harvest, have just evolved into more systematic and scientific methods and techniques.

Other regions of the world have shorter traditions of aquaculture. In North America, it is about a century old; in Africa, aquaculture production consists almost exclusively of tilapia culture in freshwater ponds and dates back to the 1940s (UNDP/NORAD/FAO, 1987). Aquaculture development has been very recent and is just gaining momentum in Australia, New Zealand, and the Pacific Island countries (Rabanal, 1988b).

Aquaculture, especially in the Western World, is very often conducted in a monotypic manner without employing a balanced approach for long-term sustainability, which would take into consideration the assimilative capacity of the ecosystem. To develop innovative, effective and responsible practices ñ maintaining the health of coastal waters, and, consequently, of the cultured organisms ñ fed aquaculture types (e.g. finfish, shrimp) and organic or inorganic extractive aquaculture types (e.g. shellfish or seaweed) need to be integrated to avoid pronounced shifts in coastal processes. Most impact studies on aquaculture operations typically have focused on organic matter/sludge deposition. However, the inorganic output of aquaculture is presently emerging as a pressing issue as nutrification of coastal waters is a worldwide phenomenon, which has not spared the Bay of Fundy (Chopin et al. in press). Conversion, not dilution, is the solution so that the ìwastesî of one resource user become a resource (fertilizers) for the others. It can frequently be heard that the development of ìalternativeî species will reduce some of the aquaculture impacts. Unfortunately, too often ìalternative speciesî in the minds of a lot of people means ìalternative speciesÖ of fishî. Even though introducing another species of fish may add up economically in the short term, rarely does it balance energetically and environmentally in the long term. It is still fed aquaculture, with extra, unconsumed, pellets and unidirectional metabolic excretion. For a balanced ecosystem approach what is needed is a diversity of co-cultured organisms, performing different processes throughout the day and seasonally, and an estimate of the proportionate biomass of each so that their metabolic processes compensate each other.