Penelitian ini bertujuan untuk mengetahui relung hewan kelas Pisces dan menganalisis kelimpahan kelas Pisces di Sungai Gong Solok Malinau menjadi potensi implementasi terhadap pembelajaran Biologi kelas X SMA. Penelitian yang digunakan adalah penelitian deskripstif eksploratif dengan pendekatan kuantitatif dan kualitatif. Lokasi penelitian dilakukan di Sungai Desa Punan Gong Solok, Malinau dan terbagi atas tujuh titik penelitian, setiap titik berjarak 1 km. Pengambilan sampel menggunakan tekmik Purposive Sampling. Analisis data pada relung ekologi yaitu dengan pengamatan langsung dan analisis kelimpahan menggunakan rumus kelimpahan relatife (Krebs, 1972). Parameter lingkungan turut menjadi hal penting dalam penelitian ini diantaranya suhu, pH, Kecerahan air, kedalaman air, Dissolved oxygen (DO), Total Dissolve Solid (TDS) dan kecepatan arus sungai. Hasil penelitian Kelas Pisces di Sungai Gong Solok Malinau ditemukan lima spesies di antaranya Gastromyzon lepidogaster, Mastcembelus unicolor, Parachela oxigastroides, Osteochilus wandersii dan Barbonymus balleroides. Analisis relung kelas pisces di Sungai Gong Solok ditemukan bahwa peran atau status fungsional spesies Gastromyzon lepidogaster merupakan hewan herbivora di tingkat trofik II, sedangkan spesies Parachela oxigastroides, Osteochilus wandersii dan Barbonymus balleroides merupakan hewan omnivore di tingkat trofik III dan spesies Mastcembelus unicolor merupakan hewan karnivora di tingkat trofik IV. Kemudian indeks kelimpahan kelas Pisces di Sungai Gong Solok yang tergolong tinggi terdapat pada spesies Barbonymus balleroides dengan nilai kelimpahan 79,61%. Kelimpahan yang tergolong sedang terdapat pada spesies Osteochilus wandersii dengan nilai kelimpahan 9,39% dan spesies Parachela oxygastroides dengan nilai kelimpahan 7,44%. Kelimpahan yang tergolong rendah terdapat pada spesies Gastromyzon lepidogaster dengan nilai kelimpahan 3,24% dan spesies Mastacembelus unicolor dengan nilai kelimpahan 0,32%. Selanjutnya dilakukan analisis keterkaitan penelitian Relung dan Kelimpahan kelas Pisces dengan pembelajaran Biologi. Hasil analisis keterkaitan penelitian kelas Pisces dengan pembelajaran Biologi, terdapat pada materi Ekologi kelas X SMA dengan Kompetensi Dasar (KD) 3.10 dan 4.10.

The research was to determine the animal niche of Pisces class and to analyze the abundance of Pisces class in Gong Solok River in Malinau as being a potential of Biological learning implementation towards 10th grade senior high school students. It was a descriptive exploratory with quantitative and qualitative approach. The research location was in Malinau Punan Gong Solok river. There were seven research points, each point was 1 km away. Purposive sampling was taken as the sampling technique. The analysis of the data in the niche of ecology was conducted by direct analysis and the abudance analysis was using abudance formula (Krebs,1972). Environmental parameter was being an important contribution in this research including temperature, pH, water brightness, the depth of water, Dissolved oxygen (DO), Total Dissolve Solid (TDS) and the river flow velocity. The results of the Pisces class research in Malinau Gong Solok river found five species, they were Gastromyzon lepidogaster, Mastcembelus unicolor, Parachela oxigastroides, Osteochilus wandersii and Barbonymus balleroides. The analysis of Pisces class niche in Gong Solok river found that the role or functional status of species Gastromyzon lepidogaster was the trophic II level of herbivores, while Parachela oxigastroides, Osteochilus wandersii and Barbonymus balleroides species were trophic III level of omnivore and the Mastcembelus unicolor was level IV trophic of carnivore. Than the abundance index of the Pisces class in Gong Solok river which was relatively high was found in Barbonymus balleroides species with an abundance value of 79.61%. Moderate abundance was found in Osteochilus wandersii species with an abundance value of 9.39% and Parachela oxygastroides species with an abundance value of 7.44%. The relatively low abundance was found in Gastromyzon lepidogaster species with an abundance value of 3.24% and the Mastacembelus unicolor species with an abundance value of 0.32%. Furthermore, the analysis of niche research and abundance of the Pisces class toward Biologi learning was carried out. The analysis result of linkage in Piscess class research toward Biology learning, was found in Ecology subject in 10th grade of senior high school within Basic Competence (KD) 3.10 and 4.10.