Flat oyster cultivation in galicia

Abstract

1. Spanish industrial firms and scientific institutions are interested in cultivating the oyster,Ostrea edulis L., for commercial and scientific purposes. Even though bays in Galicia (Northwest Spain) appear to be well suited for oyster cultivation, success has been rather limited thus far. 2. The local natural beds ofOstrea edulis are largely exhausted for several years. The Galician oyster cultivation is, therefore, at present limited to the import of middle sized oysters (mainly from Brittany) and their fattening during the favourable season, i.e. March to November, in suitable natural habitats. 3. Sufficient rates of reproduction of the fattened oysters are difficult to attain because (a) the oysters are attached to vertically arranged ropes and hence not stimulated to spawn simultaneously (large vertical gradient at critical temperature which stimulates spawning), (b) settling oyster larvae are not sufficiently attracted due to the absence of suitable natural and artificial substrates. 4. Experiments are presently being carried out employing traditional larvae collectors (tiles) and laboratory-raised oyster spat fed on phytoplankton cultures and amylaceous products. 5. Low salinities in winter, lack of oxygen in summer and adverse qualities of the natural substratum increase the mortality. Under present circumstances, fattening of middle-sized oysters appears to be still the most satisfactory method with regard to commercial view points.