Environmental factors influencing population density of freshwater clam Batissa violacea (Bivalvia) (Lamarck, 1818) in Cagayan River, Northern Philippines

Document Type : Primary Research paper



Freshwater mollusks are among the most diverse and imperiled groups of animals around the world experiencing severe population decline. This study reports the population characteristics of Batissa violacea (Lamarck, 1818) - an indigenous non-marine edible freshwater clam, in relation to the ecological condition in the largest river ecosystem in the Philippines. The B. violacea has been rated as a threatened species requiring urgent special attention for its conservation. The sampling stations were established along the downstream area of Cagayan River where the B. violacea are found covering three municipalities in the province of Cagayan. The mean density of B. violacea in Cagayan River is 1.80/m2 with a range of 0.12-11.12 clam /m2. The abundance of B. violacea in Cagayan River were found to be determined by the condition of water quality and soil substrate particularly in terms of soil pH (r=0.560; P<0.01), water pH (r=0.380; P<0.05) and total suspended solids (r=0.256; P<0.01). These results could be utilized in the formulation of the general management plan of a sanctuary established in Lallo, Cagayan, as well as the implementation of planned interconnected network of sanctuaries across the Cagayan River, to ensure a successful stock enhancement of B. violacea in Cagayan River.