Stream water and its faunal diversity are the integral part of the environmental stability and river ecosystem. To know the abundance and diversity of fin and shell fishes in relation to its water quality, a hilly stream namely Balukhali Chara in the Chittagong University Campus was investigated during December 2016 to May 2017. A total of 1904 individuals of fin and shell fishes were collected from two selected stations (S1 and S2), among which 16 species were fin fishes under four orders, nine families and fourteen genera and two species of shell fishes (crab) under one order, and two families were identified and three genera of shell fish (shrimp) under one order, two families were unidentified. As per conservation status, among the fin fishes, two species were vulnerable (VU) (Puntius ticto and Amblyceps laticeps), one was endangered (EN) (Mastacembelus armatus), ten were least concern (LC) (Dermogenys pussilus, Puntius terio, Puntius guganio, Esomus danricus, Rasbora danicornius, Lepidocephalus gutnea, Apocheilus panchax, Channa punctatus, C. orientalis and Trichopsis vittata), two species were not threatened (NT) (Danio rerio and Badis badis) and one species (Devario asamensis) recorded in this study but was not recorded and assessed (NA) in Bangladesh (IUCN 2015) and among the shell fishes, two species of crab were LC (Satoriana spinigera and Lobothelphusa woodmasoni), and two genera and three species of shrimps (Caridina sp., Macrobrachium sp. 1 and Machrobrachium sp. 2) were not identified up to species level. The abundance of Decapoda and Cypriniformes were highest followed by Perciformes, Cyprinodontiformes, and Beloniformes in both the stations.  Species diversity, species richness, species evenness and community dominance are discussed. Ranges of water quality parameters in the two stations were: air temperature15.75-32.5oC, water temperature 15.75-31.5oC, water depth 8.5–21.5cm, current velocity 0.225-0.52 ms-1, conductivity 131.50-235µS/cm, TDS 0.065-0.125 PPT, pH 6.75-7.75 and DO 5.7-8.05 mg/l.  Significant relationships of fish abundance were found with water depth (P<0.1) in S1 and with air and water temperature (P<0.1), water depth (P<0.05), conductivity and TDS (P<0.02) in S2

Key words: Fin and shell fish, abundance, diversity, water quality, hilly stream

Introduction Bangladesh is a land of rivers, which originate from the hill streams of India and Bangladesh. In Bangladesh most of the hills and hilly streams are situated in the Northeast and Southeastern part of the country which occupied about 12 percent of the total topography (Ahmed et al. 2013). These hilly streams can be used as one of the potential sources for increasing the abundance of fishes and also ensuring the biodiversity richness. Streams are necessary components of a successful ecosystem, which not only provide beauty to a community, but they also maintain water flow,  improve water quality, and  support diverse vegetation communities, fish and other aquatic wildlife habitats. Hilly stream ecosystem and biodiversity is very important due to the source of origin of different colorful fin and shellfish which live in diversified habitats consisting of clay, sand, rock, gravel, stone and boulders. Habitat characteristics are correlated with presence and absence of fishes (Gorman and Karr 1978). Again, water qualities of a river influence the fish diversity (Kow et al. 2016). The interactions of both the physical and chemical properties of water play a significant role in the composition, distribution and abundance of aquatic organisms (Mustapha and Omotosho 2005). The diverse environment support species-rich fish communities that contribute to the overall high biodiversity of river and stream ecosystems (Schiemer and Waidbacher 1992).