Distribution of Fish Species in Relation to Water Quality Conditions in Bengawan Solo River, Central Java, Indonesia

Bengawan Solo River is heavily modified into reservoirs and dams. Starting from Karanganyar to Sragen District, mass fish deaths happen up to 3-4 times a year due to organic matter pollution. The research was conducted to determine water quality during the rainy season (April 2020) and the dry season (August 2020). Samplings were carried out in three zones: the upstream zone (I) in Sukoharjo District, Central Java; the middle zone (II) in the Solo City, Karanganyar, and Sragen District, Central Java; and the downstream zone (III) in Ngawi and Bojonegoro District, East Java. Results showed that the waters of Bengawan Solo in zone I were not affected by waste. After reaching zone II, there was a heavy pollution effect. In zone III, the water quality has returned to normal levels (recovery). The fish species in zone I were dominated by exotic fish such as Nila (Oreochromis niloticus) and Jambal Sius (Pangasianodon hypothalamus). The fish species in zone II was dominated by Sapu sapu (Pterygoplichthys pardalis). In zone III were dominated by native fish species such as Jendil (Pangasius polyuranodon), Seren (Cyclocheilichthys enoplos), Bendol (Barbichthys laevis), Wader (Rasbora spp.), Keting (Barbonymus gonionotus), Daringan (Mystus microcanthus), and Tagih (Hemibagrus nemurus).