Telah dilakukan penelitian tentang kepadatan dan indeks makanan terbesar kerang kima Tridacna maxima di perairan Pulau Pasumpahan dari bulai Juni-Oktober 2003. Lokasi pencuplikan kerang T. maxima dibagi atas tiga strata yaitu strata I (sebelah barat Pulau Pasumpahan yang terdiri dari rataan karang dengan padang lamun yang banyak), strata II ( sebelah utara Pulau Pasumpahan yang terdiri dari rataan karang yang didominasi oleh makroaiga) dan strata III (sebelah timur Pulau Pasumpahan yang terdiri dari ekosistem mangrove). Pada masing-masing strata diambil tiga individu kerang T. maxima. Kerang yang didapatkan diambil lambungnya kemudian isi lambung kerang T. maxima dianalisis. Hasil penelitian didapatkan bahwa komposisi makanan alami kerang T. maxima yaitu fitoplankton dan zooplankton. Berdasarkan strata pencuplikan sampel kepadatan makanan alami kerang T. maxima terbesar didapatkan pada strata III yaitu 1813,54 individu plankton/individu kerang dan terendah strata II yaitu 1256,52 individu plankton/individu kerang. Kepadatan makanan alami kerang T. maxima tertinggi berdasarkan kelas yaitu Bacillariophyceae, kemudian diikuti kelas Crustaceae dan terendah kelas Rotifera, Nilai indeks makanan terbesar yang tertinggi didapatkan dari kelas BaciHariophyceae yaitu 30,47dan terendah kelas Rotifera yaitu 0,93. Dari nilai indeks makanan terbesar didapatkan bahwa makanan utama kerang T. maxima adalah plankton dari kelas Bacillariophyeceae dan Crustacea.

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The Density And Index Of Preponderance Of The Giant Clam (Tridacna Maxima) In The Water Pasumpahan Island, Padang City, West Sumetera. The research has been done about the density and index of preponderance of the giant clam Tridacna maxima in the water Pasumpahan Island from June to October in 2003. The giant clam T. maxima colletion sites in the water Pasumpahan Island were divided three strata i, e. strata I ( at west Pasumapahan Island still have coral reef with seagrass), strata II (at north Pasumapahan Island which the coral reef was dominated by macro algae), strata III (at east Pasumpahan Island with mangrove ecosystem). At each strata the giant clam T. maxima were collected hree T. maxima. The giant clam was taken its stomach and then the stomach of giant clam were analysed. Results of the research showed that the composition of the natural food giant clam were phytoplankton and zooplankton. Based on the samples colletion mat the highest density from natural food of giant clam T. maxima were found at strata III 1813.54 plankton/ shell individu and the lowest density of natural food of giant clam T, maxima were 1256.52 plankton/shell individu at strata II. The highest density of natural food of giant clam T. maxima based on class were Bacillariophyceae and then Crustacea and the lowest density were Rotifera. The highest index of preponderance was found from Bacillariophyceae (30.47) and the lowest were Rotifera (0.93). Food preponderance index was calculed to indicate that the phytoplankton of Bacillariophyceae (30.47) and Crustacea (27.41) were the most preference food by T. maxima.