Site selection for mollusc culture

Abstract

A great variety of mollusc species are of commercial importance throughout the world. Apart from molluscs harvested from natural fisheries, a large number is cultured. Figure 1 shows total world landings, both capture and culture, of molluscs from 1980 (3,603,426 MT) to 1986 (4,524,929 MT) with an average annual growth rate of about 3.95% (FAO, 1988). In the mollusc fishery sector the landings from aquaculture activities are high. Figure 2 shows the 1985 mollusc landings from both capture and cu lture fisheries. Over 2.8 million metric tons of molluscs were cultured in 1985 which accounted for over 65.5% of the year's total production (4,399,371 MT), obviously indicating the importance of aquaculture activities with regard to this resource group. The major division among these molluscs should be between the two classes Bivalvia and Gastropoda. The former class includes organisms like oysters, mussels, cockles, and clams whereas the latter includes organisms such as abalones and top sh ells (Fig. 3). Species belonging to the above groups have evolved in such a way that almost all kinds of marine habitats have been exploited. However, within these habitats there are often one or more environmental factors responsible for the dispersion of a particular species over given geographical areas. These limiting parameters are key factors when sites are selected for the culture of a particular species.