COMPARATIVE ALLOMETRIES IN GROWTH AND CHEMICAL-COMPOSITION OF MUSSEL (MYTILUS-GALLOPROVINCIALIS LMK) CULTURED IN 2 ZONES IN THE RIA-SADA (GALICIA, NW SPAIN)

A study was carried out in two zones in the ria de Sada (Galicia, NW S pain) with mussels (Mytilus galloplovincialis Lmk) coming from the sam e stock and cultured in rafts, from seed sized to the first split (ind ividuals with sizes between 15 and 65 mm), in order to evaluate a) the environmental differences in each location and b) their influence on growth (length and dry weight) and on chemical composition (protein, c arbohydrates, glycogen, lipid classes, and fatty acids of total lipids ). Allometric relations regarding those parameters for mussels on both locations were also determined. The mussels cultured in the inner zon e (Arnela), with a higher concentration in chlorophyll a during the pe riod studied and a smaller number of cultured mussels, present the hig hest performance in dry weight and a nearly doubled amount of glycogen than those in the outer one (Lorbe). There are also significant diffe rences in saturated, monounsaturated, nonmethylene-interrupted dienoic , and total fatty acids and sterols, the lowest content being shown by those cultured at Arnela. The mussel is an important dietetic source of polyunsaturated omega-3 fatty acids, as eicosapentaenoic acid and d ocosahexaenoic acid; both of them are beneficial for health (i.e., the treatment and prevention of cardiac ischemia). The values found range from 1 to 2% of dry weight in both locations. An indicator of the gre atest importance if the product is to be used for human food is the ra tio of omega-6/omega-3 fatty acids. Habitual diets with a ratio of ome ga-6 to omega-3 fatty acids of 12-50 are associated with a greater ris k. The value observed in this study was about 0.2 in both locations.