Fish Species Distribution and Diversity Indices of Hemavathi Reservoir, Hassan, Karnataka

The total number of fish species recorded was 42, spanning 25 genera, 13 families, and 5 orders. Cypriniformes were the predominant, accounting for 40.4% of the total, subsequent to Siluriformes (18.8%) and Perciformes (15.4%). The Cyprinidae family was the most common, representing 42.9% of the species. The most prevalent species was Oreochromis niloticus, particularly prevalent at Station 1, where it accounted for 68.31% of the total harvest. The diverse and abundant species population, especially at Station 2 in September, was indicated by Margalef's Richness Index values, which ranged from 2.00 to 3.20 toward the conclusion of the study period. At Station 3 in August 2022 the highest diversity had been observed, with the Shannon-Wiener Diversity Index (H') ranging from 2.75 to 3.12. The dominance of specific species across stations was indicated by the Simpson index (λ), which fluctuated between 0.92 and 0.97. In July 2022, the Evenness Index (J') values were at their lowest, ranging from 0.87 to 0.96, which was attributed to environmental stresses. Overall, the research suggests that the distribution of fish species is highly variable, with seasonal fluctuations impacting the species richness as well as evenness. This variability reflects the hydrological and geographical factors that have influenced the aquatic ecosystem.