Mussels have traditionally been a well-accepted seafood in many countries of Europe, particularly France, Italy and the Netherlands. But it is only in the last few decades that the potential of their cultivation has attracted any significant attention. The very high levels of production obtained by raft culture in the rias (submerged river valleys or fjords) of Galicia in Spain aroused the expectation that mussel culture may be a quick means of solving the animal protein needs of the populations of the Third World. Notwithstanding the fact that the productivity of the Galician Coast cannot be dupli cated everywhere, and that many years of work will be needed to promote and popularize mussels in many parts of the world, there is undoubtedly very considerable potential for substantial increases in the production of mussels for direct human consumption or as feed for other valued aquaculture species.
There are a number of species of mussels distributed in most parts of the world, but the most important from the point of view of aquaculture production is the blue mussel Mytilusedulis (fig. 27.13). It is widely distributed andadapts itself to a variety of ecological conditions. The Mediterranean mussel, M. galloprovincialis (fig. 27.13), is considered by someworkers to be the same as M. edulis, and the morphological differences are well within the geographic variations observed in the species. Irrespective of the taxonomic identity, there is very little difference in the biological characteristics relevant to cultivation. Another groupof mussels of importance in aquaculture includes species of Perna. The culture of the green mussel Perna viridis (= M. smaragdinus; M. viridis) (fig. 27.14) has been practised inthe Philippines for several years. The Chinese
mussel culture is largely based on the blue mussel, but the green mussel and the black mussel, M. crassitesta, are also of some importance. Experimental culture of mussels in India includes the brown mussel, P. indica. The green mussel cultured in New Zealand belongs to the species P. canaliculus (fig. 27.15), and the main species in Venezuela is P. perna.
Like other bivalve molluscs, mussels are filter-feeders, feeding on phytoplankton and suspended organic particles. In nature they live in shallow water, attached to hard substrates.
However, they can displace themselves both horizontally and vertically with the aid of the extensible foot, and attach to new substrates by the production of new byssus threads. They often attach themselves to the shells of other mussels, forming large mussel congregations.