Diversity Abundance and Distribution Patterns of Species Composition of Gastropods at Dapya Island, Barangay Day-Asan, Surigao City, Surigao Del Norte

This study investigates the gastropod diversity, relative abundance, and distribution pattern of the gastropods present in Dapya Island, Barangay Day-asan Surigao del Norte, Philippines. The sampling was done 2 - 3 days during the lowest low tide at daytime employing the transect-quadrat method and established three sampling stations. A total of 496 individuals distributed among 12 genera and 25 species of gastropods were identified in the study area during the sampling period. The three most abundant species in the area namely Nerita chamaeleon, Nerita polita, Nipponacmea concinna with relative abundance of 16.73%, 11.09%, and 9.88% respectively. The result of species diversity varied between stations; Station 1 was the most diverse among the 3 stations since 25 species of gastropods were identified and was evenly distributed, as it has the highest total of evenness but it has low dominance while station 2 has the highest species richness (267) and dominance but low in diversity. On the other hand, station 3 was highly distributed but had the lowest species richness. All gastropod species in the area were distributed at random and mostly inhabited the rocky substratum. In addition, the CCA between gastropod species and selected water quality parameters revealed that the pH level has a negative effect on the diversity of gastropods specifically the V. turbinellus, Conus sp., Angaria sp., and Cerithium coralium. Whilst, Salinity, DO, and water temperature have a positive correlation to the other species and do not negatively influence the species diversity of gastropods in the area, instead they increase the richness and diversity of the species. Furthermore, analysis of variance (ANOVA) proved no significant difference in the abundance of gastropods in the three sampling stations (total value of 0.609 level of significance). This means the kind of stations cannot affect the abundance of gastropods. Thus, the area was considered diverse since there are no consequences for the illegal fishing and exploitation that happened inside the MPA. Hence, it is still recommended to be more vigilant in the protection and management of the MPA.