-10- The amount of contamination would, variables as tides, in turn, winds and currents. such 4s migration of the fish, be subject to such Biological vartables, mortality, influx and outflow of breeding populations and their young also could contribute to the variation. In order to determine the extent of the variation, calcu- lations of the coefficient of variation (V) were made (1) by families, using four or more specimens for the calculations (Table 2) and (2) by date, using muscle tissue from all fami- lies combined (Table 3). The data in Table 2 indicate that there are differences in the coefficient of variation between familles, high in goatfish and mullet, highest in viscera. i.e., and between tissues, distinctly averaging The average coefficient of variation for all families and all tissues combined was 56 per cent. By omitting the goatfish and mullet in the calculations the average is lowered to 37 per cent. The latter value is similar to that found for algae (37%) (Palumbo, 1957) and for invertebrates (Bonham, 1957). The fact that goatfish and mullet prefer the open sandy bottom areas of the reef, moving in schools from island to island may account for the higher coefficient of variation in these fishes. The average coefficient of variation is much greater when samples of mixed families or species are used. the data for muscle tissue are summarized, coefficient varies from 16 to 209 per cent. Table 3, indicates in which that the The coefficient of variation of muscle in all the collections averages 97 per cent,