Variability in esterase (EST), alkaline phosphatase (AlKp) glutamate oxaloacetate transaminase (GOT) and aspartate aminotransferase (AAT) loci in the plasma (pl), epaxial muscle (mus) and liver (li) tissues within and among the local populations of damselfish, Stegastes nigricans, was conducted using horizontal starch gel electrophoresis. Samples were obtained from four selected reef sites along Iligan Bay; Clarin (Misamis Occidental), Buru-un (Iligan City), Lugait (Misamis Oriental) and in Sagay (Camiguin Islands). Allelic frequencies in each protein locus were computed as basis in comparing variations within and among populations. Results revealed that values on the number of effective alleles (ne), heterozygosity values and allelic differentiation (dT) of the 4 gene loci showed that Buruun (2.142, 0.546) and Lugait (2.111, 0.540) are more similar than Clarin (1.880, 0.468) and Sagay (1.8166, 0.449). These results suggest that expression of genetic variability among natural populations could be possibly due to environmental heterogeneity with stable and unstable habitats.
