Density, Water Quality Suitability and Size Distribution of Pokea Clams (Batissa violacea var. celebensis, von Martens 1897) at Lasolo River Southeast Sulawesi

Abstract

Kepadatan dan distribusi ukuran kerang pokea relatif berbeda-beda disetiap tempat dan waktu yang dipengaruhi oleh kualitas lingkungan perairan. Penelitian ini bertujuan untuk mengetahui kepadatan kesesuaian kualitas perairan, dan distribusi ukuran kerang pokea di Sungai Lasolo Sulawesi Tenggara.  Sampel kerang pokea dikumpulkan secara acak di seluruh bagian perairan setiap bulan selama 1 tahun di Sungai Lasolo Konawe Utara. Sampel kerang dikumpulkan menggunakan luas sapuan alat tangkap tangge (alat tradisional) sebanyak 6 kali tarikan.  Pengambilan sampel kualitas air dilakukan bersamaan dengan pengambilan sampel kerang.  Kepadatan kerang antar tempat dan waktu pengamatan dianalisis menggunakan uji Mann-Whitney.  Preferensi pokea pada kualitas perairan dianalisis menggunakan Analisis Komponen Utama (PCA) dan Analisis Kelompok (CA) pada paket program statistik multivariat (XLSTAT).  Hasil analisis menunjukkan kepadatan daerah tengah muara sungai berbeda nyata (lebih tinggi) dengan pada daerah awal dan akhir ditemukan ke arah hulu (kepadatan terendah) dan ke arah muara, sedangkan kepadatan kerang pokea tidak nyata berbeda di setiap bulan pengamatan.  Kerang pokea dominan ditemukan pada ukuran kecil (1,62-2,10-3,09-3,57 cm). Ukuran kerang pokea terdistribusi pada seluruh bagian perairan dan ditemukan melimpah pada bulan Mei dan Juni.  Kerang pokea cenderung menyenangi kualitas perairan yang berarus lambat, kecerahan tinggi dan perairan dalam.The pokea density and its size distribution are different in every place and time which influenced by water quality. This study aimed to determine the density and suitability of water quality, and size distribution of pokea at Lasolo River, Southeast Sulawesi. Pokea samples were collected randomly in all water segment every month for 1 year in the area of Lasolo River, North Konawe. Some samples of pokea were collected using the wide range of tangge fishing gear (traditional tool/ traditional fishing gear) as much as 6 pull times.  In the process of collecting the sample of water quality, it was done simultaneously with the samples of shell. The shell density in every place and time was analyzed using the Mann-Whitney test. The preferences of pokea in water quality were analyzed using Principal Component Analysis (PCA) and Group Analysis (CA) in the package of multivariate statistical program (XLSTAT). The results of this analysis showed that the density of the middle of estuary was significantly different (higher) than its density in the initial and final regions which found upstream (lowest density) and in the estuary area, while the density of pokea was not significantly different in each month of observation. The pokea were dominantly found in small size (1.62-2.10-3.09-3.57 cm). The size of the pokea were distributed in all water segment, which were so many in May and June. The preferences habitat of pokea were the slow-flowing, high-brightness, and deep water