The present study aims to understand the spatio-temporal dynamics in habitat ecology and fish assemblage and determine the relationship of habitat transition and fish distribution in a large riverine-reservoir cascade system (Sardar Sarovar Reservoir part in Madhya Pradesh). This study was carried out along a 125-km riverine-reservoir interface (RRI) during 2018–2020. The study showed presence of a total of 110 fish species (104 spp. in upstream main Narmada River stretch excluding reservoirs, 56 in RRI, and 39 in Sardar Sarovar reservoir). We recorded 50 species common in upstream riverine stretch of Narmada and the RRI while RRI uniquely harbored 3 native species (Chitala chitala, Labeo boga, Salmostoma phulo) not previously reported from Narmada River stretch upstream. The similarity percentage (SIMPER) analysis showed presence of S. phulo causing 27.91

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 − λ), 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.

Length-frequency data of Nile tilapia (Oreochromis niloticus) was studied using 1250 specimens of both sexes combined with maximum length and weight of 44.5 cm (TL) and 1050 g respectively through gill net catch at different landing sites of Halali Reservoir, Madhya Pradesh. The data were grouped into classes of 10-mm intervals and various parameters of population dynamics of fish were analysed and computed using the FiSAT-II software package (FAO-ICLARM Stock Assessment Tools). The length-weight parameters were found to be at W = 0.001 L 2.96 where b = 2.96 and a = 0.001. Growth parameters L∞ and K of the species were L∞ = 46.73 cm and K = 0.63/year respectively; the annual rates of natural (M) and fishing mortality (F) were found to be 0.60 and 0.72 respectively. The estimated values for the exploitation rate (E) using the length-converted catch curve and virtual population analysis were 0.54 and 0.42 respectively. The recruitment pattern shows that O. niloticus was recruited in the fishery during April with one peak. Based on the data analysis, the stock in the Halali Reservoir does not exceed the maximum fishing pressure (Emax = 0.55) and there is selective mortality towards adult fish sizes. The introduction of Nile tilapia improved the total catch per unit of effort (CPUE), as well as increased the number of active fishers. Conversely, a significant reduction in the CPUE of other commercially important indigenous species was observed after the introduction of Nile tilapia in the reservoir. Therefore, for management purpose, this study suggests that the existing effort in terms of gill net mesh size which target size (TL-15.0 to 25.0 cm) individuals of length group is to be increased to exert more fishing pressure on Nile tilapia population in the reservoir to decline its abundance in the long term.

The present study describes the length-weight relationships (LWRs) of 18 fish species from a large tropical reservoir, Panchet, in the Damodar River basin, one of the main tributary of the largest river Ganga in India. A total of 2419 individuals represented by 18 species belonging to 9 families were sampled between November 2014 and June 2016. The b values ranged from 2.469 for Trichogaster chuna to 3.428 for Ailia coila. All the regressions were highly significant (p<0.001). The results revealed positive allometric growth for seven species (b>3, p<0.05), negative allometric growth for seven species (b<3, p<0.05) and isometric growth for four species (b=3, p>0.05). This study represents the first reference on the lengthweight relationship of Trichogaster chuna from a reservoir ecosystem. This is the first report on LWRs of five fish species viz., Puntius terio, Pethia conchonius, Sperata seenghala, Ailia coila and Trichogaster chuna from an Indian reservoir. This study provides basic data for future stock assessment studies and management programmes from Panchet Reservoir as well as for complementing the comparisons of LWRs from other ecosystems.

Fish assemblage structure in Panchet, a large tropical reservoir along river Damodar, major tributary of river Ganga in India, was studied along the spatial gradient of the impoundment. Fish samples were collected bimonthly from October 2014 to September 2016. Fish community structure in terms of species composition, relative abundance, and trophic and conservation status was recorded. Spatial fish diversity was analyzed from riverine, transitional, and lacustrine zones. Sixty-two fish species were recorded wherein the family Cyprinidae dominated in number of species (26) followed by Bagridae (5). Shannon diversity index, evenness index, and species richness did not reveal significant variation (p > 0.05) across different zones. Relative abundance of individuals and species richness were maximum in the transitional zone and minimum in the lacustrine zone. Multi-dimensional scaling of fish assemblage revealed similar pattern in the riverine and transitional zones. Trophic guild of fishes indicated dominance of carnivorous species followed by planktivores. Conservation status (IUCN 2017.3) showed 4 fish species in Near Threatened category. The study suggests conservation of fish habitats to maintain diversity and sustained production. The baseline information generated in the study will be beneficial for monitoring the alteration in fish assemblage, conservation of fish diversity, and management planning.