Fish Species Diversity in The Krasak River Srumbung Subdistrict Magelang Regency Central Java

Abstract

This research aims to explore the diversity of fish species in the Krasak River, Central Java, where information on fish composition is still limited, in contrast to the Progo River and Elo River, which have been studied by several researchers. This river, originating from the slopes of Mount Merapi, has water characteristics with volcanic material and variations in current and substrate. The research was conducted from October to November 2025 at three observation locations using purposive sampling. All the fish caught were identified to the species level, counted for their individual numbers, and analysed using the Diversity Index (H'), Evenness Index (E), Dominance Index (D), and Relative Abundance (RA). Environmental parameters, including temperature, pH, current, depth, brightness, and substrate, were also measured as supporting data. The results show that the fish community in the Krasak River comprises 221 individuals across 12 species and 6 families. The Diversity Index shows low values (0.647-0.882), and the Evenness Index is also low (0.260-0.355), indicating an uneven distribution of individuals among species. The species Mystacoleucus obtusirostris became the dominant species, accounting for 53.39% of the total individuals captured. This study provides an initial overview of fish diversity in the Krasak River and is expected to be useful for fisheries resource management and further research.