Fish assemblage, ecosystem status and potential impact of Nile Tilapia in Halali Reservoir of Central India

The pattern of spatial fish assemblage, diversity, habitat, and potential impact of Nile tilapia (Oreochromis niloticus) was studied in a tropical reservoir of central India during June 2018-July 2019. A total of 21 species under six orders nine families and 18 genera were recorded which is comparatively low than previous records. The fish abundance similarity showed a maximum similarity of 78% between site 1 and site 3 clusters. The results of species composition showed increased abundance of O. niloticus species (> 80%) in the fishery and have now established feral population in the reservoir. The mean Simpson dominance index (1 - lambda), the Shannon diversity index (H '), Pielou's evenness index (J ') and Margalef's richness index (d) were determined for three different sites followed by Mann-Whitney U test which showed a significant difference at spatial scale. Bray-Curtis cluster analysis of physicochemical parameters showed a similarity of 96% between site 1 and site 2. Comparison with the previous study three physicochemical parameters (total alkalinity, total hardness and chloride) showed the considerable changes. Relationships between fish assemblages and environmental parameters were examined by canonical correspondence analysis (CCA). Six physicochemical parameters (i.e., DO, pH, Nitrate, Mg, Phosphate and Silicate) showed statistically significant to shaping fish diversity (p < 0.05). The high value of dissolved oxygen coupled with low biochemical oxygen demand and other nutrient levels indicates that the water body is moderately oligotrophic in nature. The responsible factors for declining indigenous fish population and threats are discussed. The study recommends specific management measures which could be useful to develop a sustainable fishery practice vis-a-vis conservation of fish diversity.

Automated summary

The study found that the abundance of Nile tilapia in the reservoir is high and they have established a feral population. There are significant differences in fish abundance between different sites and considerable changes in physicochemical parameters.