The density of blood cockle (Tegillarca granosa) population in the river estuary of industrial area

Blood cockle (Tegillarca granosa) has a high value so that it can be utilized as a source of community income. T. granosa could be easily found in the coastal area, which is the location of its collection activity. However, fishing activities are thought to be a trigger for the decrease in production of T. granosa. Intensive T. granosa collection activity has serious impact upon the resources existence. This research aims to identify the density of T. granosa in the waters around an industrial area. Swept area was carried out in the sampling process. Purposive sampling method was used to determine the sample. In each zone, there were 3 stations with 5 repetitions in each zone per month (total 3 month research process). This study also measured the water quality by adding HNO₃ to the water sample until the pH reached <2. The result showed fluctuations in the T. granosa population, in January was 0.69 ind m^-2; in February was 0.44 ind m^-2; and in March was 0.5 ind m^-2. Measurement of water quality illustrated the absence of varied changes between parameters (temperature, salinity, pH, brightness, dissolved oxygen, suspended solids, and sediments). Shellfish collection and water quality are becoming factors that affect the density of T. granosa. The disposal of industrial waste also inhibits the growth of T. granosa. Proper monitoring of T. granosa collection activity and water pollution is needed for balance ecosystems of T. granosa living areas.