Keanekaragaman Ikan dan Hubungannya dengan Faktor Fisik-Kimia Air di Danau Toba, Kecamatan Pangururan, Kabupaten Samosir, Sumatera Utara

Abstract

Fish diversity is an important indicator in assessing the health of aquatic ecosystems. The ecosystem reflects the balance between species and environmental conditions. Toba Lake is the largest volcanic lake in Southeast Asia, the lake holds significant potential for fisheries resources; however, its sustainability may be threatened by declining environmental quality, particularly related to physico-chemical water factors. This study was conducted in Pangururan District, Samosir Regency, North Sumatra. The aim was to determine fish diversity and to analyze its relation to physico-chemical water parameters. The method used was purposive sampling at three observation stations: the port area, market area and domestic discharge site. The results showed that the fish collected from Toba Lake consists of 5 orders, 5 families, 6 genera and 7 species. The species with the highest density is Amphilophus citrinellus found at stations 1, 2 and 3. The Shannon-Wiener diversity index (H’) ranged from 1.501 to 1.803, indicating a low level of species diversity. The evenness index (E) ranged from 0.838 to 0.926, indicating a high level of species evenness. Based on correlation analysis revealed that physico-chemical factors— particularly Biological Oxygen Demand (BOD), nitrate and phosphate—had a very strong influence on fish diversity. Dissolved oxygen (DO) showed a strong influence, while temperature and pH had a moderate influence. Meanwhile, light penetration and light intensity had a weak influence on fish diversity.