Seaweeds are of direct importance to man as a dietary supplement/food additive/source of industrial feedstock and as a base for synthesis of a wide range of chemical products. They are of indirectly importance as contributors to natural food chains and habitats supporting commercially important marine fish and shellfish. Except for a few areas of the world however; such as in the Asian region/their potential for contributing to coastal economies of developing countries has been largely unrealized to date and there is a general lack of information on how this resource may be used productively. As noted recently by Caddy and Fischer (1984): "Seaweeds pose the same questions to the resource manager with respect to national harvesting strategy as do commercially important marine animals on the one hand, and the optimal management of forest and pasture stands in the terrestrial context, on the other. The same important questions should be asked in relation to harvesting strategy, namely:
"(1) Where are the resources, of what kind, and how much? What are the possible alternative uses and markets for these kinds of resources?
"(2) What is the rate and time of harvesting needed in order to maintain a sustainable optimal harvest of the wild resources?"(3) What are the appropriate levels of investment in manpower and equipment needed to achieve the above optimal harvesting rate in both wild and cultivated systems without wasting scarce economic resources?
"(4) What, if any, are the indirect impacts of harvesting wild crops or farming on other resources in the ecosystem?"
Although an attempt at addressing the first of these considerations was made by Michanek (1975), and the second by Naylor (1976) and McHugh & Lanier (1983), we are clearly still at an early stage in beginning to realize the economic potential of this important grouping of organisms. The large scale culture of unicellular algae, and the culture and wild harvest of seaweeds or macrophytes are potentially an important addition to those other major spheres of human activity, namely agriculture, forestry and fisheries, which now provide most of our naturally renewable organic materials.
The utilization of marine algae is still in its infancy, and despite numerous articles scattered through the scientific literature there are few general accounts that provide the manager of coastal seaweed resources with practical information. There is a general lack of guidance on the management of wild seaweed resources; some of which are unexploited, some overexploited. Many are of ecological importance to fisheries and several form the basis for the rapidly growing field of seaweed farming.
Paradoxically, in comparison with mariculture of marine fish and shellfish, the technical problems of growing marine algae commercially are relatively simple, and are fairly well understood, as can be seen by the case studies included here. In contrast, the problems of market development for algal seaweed are generally more difficult than for the animal seafoods. This is because more sophisticated treatments are required for using the algae either directly as food, or extracting them to make a wide range of valuable chemicals available.
The chemical applications of seaweeds in particular support sophisticated, capital-intensive industries in developed countries as extraction and purification of a wide variety of products is now undertaken. Here, economic constraints both with respect to capital, equipment and labour intensive cultivation methods, and generally low unit prices paid for the product, are the main constraints, but are only touched on briefly here. A companion volume to the present series of case studies is now being planned, which will deal in more detail with special topics relevant to seaweed harvest and culture, such as approaches to management and assessment of seaweed resources, processing, legal aspects and economics.
References
Caddy, J.F., and W.A. Fischer. FAO interest in promoting understanding of world seaweed resources, their optimal harvesting, and fisheries and ecological interactions, Hydrobiologia, 116-117:355-62
Michanek, G. Seaweed resources of the ocean. FAO Fish.Tech. Pap., (138):127 p.
McHugh, D.J., and B.V. Lanier. The world seaweed industry and trade: developing Asian producers and prospects for greater participation. ADB/FAO INFOFISH Market.Stud., (6):30 p.
Naylor, J. Production, trade and utilization of seaweeds and seaweed products. FAO Fish. Tech.Pap.. (159);73 p. Issued also in French and Spanish
