Kepadatan Populasi dan Pertumbuhan Kijing Lokal (Pilsbryoconcha exilis) di Sungai Simangayat dan Waduk Samak Kabupaten Labuhanbatu Selatan Provinsi Sumatera Utara

Abstract

The Simangayat River and the Samak Reservoir are waters in South Labuhanbatu Regency and both are waters that have different characteristics. The Simangayat River and Samak Reservoir are inhabited by the Freshwater Mussel (Pilsbryoconcha exilis) which is a native Indonesian bivalves. The purpose of this research was to determine the population density of the freshwater mussel (P. exilis), the growth of the Freshwater Mussel (P. exilis), and the relationship between the population density of the freshwater mussel (P. exilis) and water quality. The research method used is purposive sampling method. The research was conducted from October to November 2022. Freshwater Mussel obtained from the two study locations totaled 644 individuals. The results showed that the population density in the Simangayat River was 7,356 ind/ha and in the Samak Reservoir the population density of mussels was 6,923 ind/ha, the distribution of the length frequencies of the local mussels was 22-141 mm, the growth pattern of the local mussels was negative allometric where the growth in length was more dominant over weight growth, the asymptotic length of the Freshwater Mussel at station 1 was 142.5 mm with a growth coefficient value of 0.61/year, and the theoretical age when the shell length was zero (t0) was -0.76 year and the time required for reach its asymptotic length for 24 months, at station 2 the asymptotic length of the Freshwater Mussel is 118.5 mm with a growth coefficient value of 1.01/year, the theoretical age of the shells when the shell length is equal to zero (t0) -1,005 year and the time needed to reach its asymptotic length is 13 months. The results regarding the relationship between population density and water quality obtained 3 parameters that have a strong degree of relationship, namely current speed which is positively correlated with a correlation value of 0.683, then pH which is also positively correlated with a correlation value of 0.680, while temperature is negatively correlated with a correlation value of -0.603 , parameters that have a moderate level of relationship and are negatively correlated are depth with a correlation value of -0.406, parameters that have a low level of relationship and are negatively correlated are C-Organic with a correlation value of -0.357 and dissolved oxygen content with a correlation value of -0.283 and parameters having a low level of relationship also has a negative correlation, namely brightness with a correlation value of -0.112.