ALLOZYME VARIATION IN THE PACIFIC OYSTER CRASSOSTREA-GIGAS ALONG THE COAST OF TAIWAN

Nine populations of the oyster Crassostrea gigas, were assayed for all ozyme variation by starch gel electrophoresis. Three of the seven enzy me loci investigated are polymorphic: Lap, Mpi, and Pgi. Significant h eterozygote deficiency was found in ail seven Taiwan populations but n ot in the two populations of the Penghu Islands. Low levels of genetic variability (p = 0.14-0.42; H = 0.044-0.084) and little genetic diffe rentiation (Nei's D < 0.01) were found among populations. Individuals with Lap heterozygotes were smaller than those with homozygotes in one population (p = 0.03) but this difference was statistically insignifi cant when adjusted significance level for multiple tests was used. Our results suggest that environmental factors may be important in determ ining regional differences in oyster size and shape.