Assessment of the Shellfish Resources of Balete Bay, Davao Oriental

Abstract

Assessment of shellfish •resources in Balete Bay, Davao Oriental was made from March 1994 to January 1995 to determine their status and level of exploitation of most commercially exploited species in the area. Sampling followed a modified technique of the standard procedure for soft-bottom organisms. Monthly size measurements of Strombus urceus and Placuna placenta, the most commercially exploited species were made. Representative samples of other species were collected for identification purposes while some abiotic factors were also monitored. About 55 species were identified With total density ranging from less than 1 to 7 inds./m² . S. urceus was the most dominant species being the highest in both total density (7 inds./m²) and relative abundance (24%). They were most abundant in S3 and S4 that have sandy-muddy to sandy substratum with vegetation. P. placenta, with a total density of 3 ind./m² and relative abundance of 9% was mostly confined in the muddy substratum of S1 and S2. Some species were ubiquitous while others were restricted in occurrence. Shannon's Diversity Index revealed that S2 and S3 were more diverse areas and S6 had low diversity. Rarefactions Method showed that S3 was high in species richness while Sl and S5 were less rich in species. Frequency and size frequency distribution of S. urceus and P. placenta showed a fluctuating trend throughout the sampling   period and correlation test on physico-chemical parameters showed their community zonation is strongly influenced by granulometry gradients from landward to the seaward zone.