The study was carried out in Alwara wetland, a seasonally open floodplain wetland connected to the Yamuna River in the Kaushambi District of Uttar Pradesh, - to estimate the fish community structure in relation to habitat variables across three seasons. Altogether, 62 fish species comprising 9 orders, 23 families and 50 genera were recorded, including 5 exotic species. As per IUCN categorisation, 5 species viz., Wallago attu, Ompok bimaculatus, O. pabda, Chitala chitala and Ailia coila are near threatened and Clarias magur is endangered. Cypriniformes (40.32%) were the most dominant order, followed by Siluriformes (22.58%), Perciformes (19.35%), Synbranchiformes (4.84%), Clupeiformes and Mugiliformes (3.23%), Tetraodontiformes and Beloniformes (1.61%). The Shannon-Wiener diversity index (H') ranged from 3.421 (post-monsoon) to 3.877 (monsoon) with an uneven abundance of fishes as indicated by the evenness index (post-monsoon = 0.6951 to monsoon = 0.8186). Water quality parameters were significantly (p<0.05) different across the seasons except specific conductivity, silicate-Si, phosphate-P, and dissolved organic matter (DOM). Certain sediment quality parameters differed significantly (p<0.05) across the seasons. Canonical correspondence analysis (CCA) was used to study the association of 27 commercially important fish species with 6 important water quality parameters and provided the baseline information on fish community structure. We observed growth and recruitment overfishing, which may affect fish diversity and its sustainable utilisation to support fishers' livelihoods.

Heavy metal enrichment in river sediments poses a significant risk to human and aquatic health. The Yamuna River faces severe challenges due to untreated industrial and domestic wastewater discharge. The study evaluates sediment metal content, ecological and human health risks, and potential sources. Results showed Cd and Pb exhibited moderate to severe contamination and displayed ecological risk based on contamination factor, enrichment factor, and potential ecological risk. According to synergistic indices (pollution load index, PINemerow, toxic risk index, contamination security index, mean probable effects level quotients, and probability of toxicity), the sediment in the Yamuna River doesn't seem to have a risk or enrichment from combined metals. Cd and Pb mainly originate from anthropogenic sources. Hazard index (< 1) and carcinogenic risk (2.2 x 10(-7) to 4.7 x 10(-5)) assessments suggest metal didn't pose any risk to humans exposed to sediment. The present study aids in developing pollution control strategies for the Yamuna River.

The objective of the investigation was to explore the abundance, composition, and diversity patterns of the fish fauna along the temporal and spatial scale and study the influence of environmental parameters on the fish assemblage in the Rihand reservoir, a large sub-tropical Indian reservoir in India. On the temporal scale, the highest abundance was recorded in the summer season and the lowest in the monsoon season. While on the spatial scale, the highest abundance was recorded from the riverine and the minimum from the lacustrine zone. The highest species richness and diversity were recorded from the riverine zone followed by the transitional and lacustrine zones, respectively. The analysis of the variance of fish abundance revealed insignificant differences between the riverine and the transitional zones. The trophic guild analysis indicated the dominance of carnivores. The output of canonical correspondence analysis depicted the significant influence of the physico-chemical traits on the abundance of fish species. The transparency and specific conductivity were found to be the most critical factors affecting fish assemblages in the Rihand reservoir. This study generated important baseline ecological information that would be useful for the monitoring, conservation, and management of the reservoir ecosystem.

For effective and sustainable water management, assessing the water quality and identifying potential sources that threaten the river system are crucial steps. In the present study, spatiotemporal variation of 20 hydrochemical variables, water quality indices, and multivariate statistics were applied to evaluate the quality of Yamuna River water. In the middle and lower stretch, the levels of electric conductivity (EC), total dissolved solids (TDS), turbidity, dissolved organic matter (DOM), chemical oxygen demand (COD), and nutrients were higher than in the upper stretch. Based on the trophic state index, the upper, middle, and lower stretches were mesotrophic, moderate, and low eutrophic in nature, respectively. In the drinking water category, the water quality index (WQI) ranged from almost good (upper stretch) to inappropriate (middle and lower stretch). Nemerow pollution index (PINemerow) and the comprehensive pollution index (CPI) indicated that most sites were strongly and moderately polluted, respectively. Various point and nonpoint sources of pollution deteriorated the quality of Yamuna water. Spatial cluster analysis divided eleven stations into three groups based on water variables similarity. Discriminate analysis indicated that water temperature, flow, turbidity, pH, dissolved oxygen (DO), magnesium hardness (Mg-H) and COD were the most influencing variables seasonally, while water flow, pH, chloride (Clˉ), DO, Mg-H, and nitrate–N were for spatial variation in Yamuna water quality. Five potential sources were identified using principal component analysis (PCA); anthropogenic, natural, agricultural non-point sources, metrological, and seasonal factors. This study emphasizes the importance of using multivariate statistical techniques to identify variability patterns and develop management plans to improve river water quality by identifying the key variables responsible for maximum deterioration.

The River Tamas is a right-bank tributary of the River Ganga flowing through the states of Madhya Pradesh and Uttar Pradesh, India. It originates in Jhukehi village in the Satna district of Madhya Pradesh and after 268 km it joins with the River Ganga at Sirsa, Prayagraj, Uttar Pradesh. The river has a diverse habitat and harbours a variety of flora and fauna. More than 70 fish species reside in the river, along with other biotic communities. A barrage, named Tons and situated at Bakiya village, was commissioned in 1992 for hydro-electric purposes. The continuity and volume of water in the river have been disturbed due to the construction of this barrage and it has changed the ecology and biodiversity. Keeping the ecosystem intact requires that environmental flow calculations be made of the river at the barrage. An attempt has been made to estimate the environmental flow requirement using a desktop hydrological method. Based on the flow duration curve (a hydrological method of flow estimation), the environmental flow for the River Tamas has been calculated using Global Environmental Flow Calculator software. Our calculation are based on flow discharge data received from the Tons Barrage Authority at Bakiya for the period January 2006 to December 2017. Average annual discharge was calculated from the recorded maximum (151.46 cumecs in 2016) and the minimum, 13.53 cumecs in 2007. Mean Annual Runoff was calculated as 1607 Million Cubic Meter with Coefficient of Variation =0.799. To maintain the river in the “slightly modified” class of Environmental Management Class, 27.8 % of Mean Annual Runoff discharge should be released into the river to largely maintain the biodiversity and habitat, while about 57% of Mean Annual Runoff discharge is required to maintain this river in pristine condition. This is a preliminary study to determine the water requirements for healthy habitat and biodiversity of the Tamas river.

Ganga is the most prestigious river of India. The COVID-19 lockdown may have forced us to stay indoors, but it has been boon for pollution-ridden Ganga and Yamuna. Plankton is tiny organisms drifting with water current, influenced by river physical and chemical factors. During lockdown anthropogenic factors were reduced which affected water and plankton quality. Plankton samples were collected from the upstream of the river Ganga (Shankerghat, latitude 25030’28” N and longitude, 81052’10”E) and Yamuna (near boat club, latitude 25024’29”N and longitude 81054’50”E) at Prayagraj, during national lockdown. In the before lockdown period (2019), total 28 planktonic taxa were recorded from the river Ganga, among them 10 taxa from Bacillariophyceae, 15 from Chlorophyceae and 3 from Myxophyceae. While during LD period total 54 genera with 86 species was recorded (Bacillariophyceae 10 taxa, Chlorophyceae 23 taxa, Myxophyceae 9 taxa, Euglenophyceae 2 taxa, Dianophyceae, 1, Rotiferea 7 taxa, Protozoa 2 taxa). Various species of green algae were observed in this small period of lockdown, some species were not observed since a long, like Pediastrum tetras, Scenedesmus abundans, Ankistrodesmus fusiformis, and Brachionus angularis. Various species of phytoplankton and zooplankton were in reproductive phase because river was flowing silently, without any internal and external disturbance. Ganga was more affected by anthropogenic activity and factory discharge than Yamuna So lack of chemicals in the water and minimum human interference favoured auto rejuvenation of Ganga in terms of plankton quality, diversity and reproduction behaviour. Such type of environmental changes may stimulate for origin of new species and disappear or reappear of various aquatic species.

The assemblage pattern of macrobenthic invertebrates concerning environmental variables on a spatiotemporal scale from river Tamas, a tributary of river Ganga was studied during the period 2017–2019. Altogether 27 genera of Gastropoda (10), Bivalvia (7), Insecta (7), and Annelida (3) belonging to 15 families, and 9 orders were recorded across six sites. Species richness at Itahara (S1), Madhavgarh (S2), Bakia upstream (S3), Bakia downstream (S4), Chakghat (S5), and Panasaghat (S6) was found to be 12, 13, 14, 22, 14 and, 10 respectively. Gastropods (44%) were the most dominant class, followed by Bivalvia (33%), Insecta (16%), and Clitellata (7%). Analysis of Variance (ANOVA) showed that physicochemical parameters (depth, water velocity, total alkalinity, dissolved oxygen, sp. conductivity, total dissolved solids, total hardness, calcium, and phosphate) and sediment quality parameters (available nitrogen, available phosphorus, and specific conductivity) differed significantly across sites (S1–S6) (p < 0.05). The Shannon–Wiener index (H’) varied from 1.23 (S6, monsoon) to 2.75 (S4, post-monsoon), while the evenness index ranged between 0.76 (S2, monsoon) and 0.91 (S6, post-monsoon). The H’ index was found to be 2.84, and the evenness index was 0.63 for the studied river stretch. The variation in the altitudinal level, availability of food items, suitable substrate habitat, and the water and sediment quality parameters mainly governs the assemblage pattern of macrobenthic invertebrates. Based on the Welch pattern, the studied river stretch falls under the river health category as moderate status, i.e., 1 < H′ < 3. Our result underlines the current status of the macrobenthic invertebrate community structure and infers for improving the health of river Tamas for sustainable management.

River Cauvery, the major peninsular river in India has been impounded by a number of dams and barrages which has totally modified the habitat of the river impacting the migration of fishes. A recent survey revealed that the entire river stretch has reduced depth and regulated flow especially during lean season allowing the submerged macrophytes to proliferate. Different habitat parameters of the river were described in the light of impoundments. The changed behavioural pattern of the migratory fishes against the river barricades at Mayanoor, Grand Anicut, and Lower Anicut has been described. Cornered fishes below and above the barrage are indiscriminately targeted using modified fishing gears specially designed for manipulating the migrating fish behaviour. The necessity of fish species-specific migration-friendly structures below the barrage was identified for sustainable fishery of the river.

The Tamas River is a right-bank tributary of the River Ganga, originating from Jhukehi village in Madhya Pradesh and meeting up with the Ganga at Sirsa, Prayagraj, Uttar Pradesh, India. An investigation was carried out in six sites at (Itahara, S1), (Madhavgarh, S2), (Bakiya upstream, S3), (Bakiya downstream, S4), (Chakghat, S5) and (Panasaghat, S6) of the river to document the fish diversity, seasonal variability, and impact of environmental variables on fish species composition during the period 2017 to 2019. Altogether 75 fish species belonging to 54 genera, 23 families, and 10 orders were recorded. Fish species richness at (S1), (S2), (S3), (S4), (S5), and (S6) and was recorded as 9, 39, 38, 13, 61, and 49, respectively. Family Cyprinidae with 31 species contributing 41% was the most dominant family, followed by Bagridae (8%) and Schilbeidae (6.7%). Seasonal variation in fish species richness and diversity indices were observed in the river stretch. Maximum species richness (45) was observed at S5 during monsoon and a minimum (6) at S1 during post-monsoon. As per the International Union for Conservation of Nature categorization, 10 out of 75 fish species recorded from the river were considered to be threatened. Three exotic species, namely Cyprinus carpio, Oreochromis niloticus, and Hypophthalmichthys nobilis, were recorded at some stretches, which may be a concern for native fish diversity. Environmental variables like water temperature, pH, dissolved oxygen, water velocity, and alkalinity influenced the fish community structure. The selected (S1–S6) stretch of the river falls under the category of Slightly Impacted River based on the Shannon Index (H'>3). The present investigation was the first assessment of rich fish diversity covering the maximum stretch of river, which supports many important and small indigenous fishes for conservation.

The understanding of patterns in fish assemblages is imperative for management and conservation plans. There is a dearth of information on the environmental factors affecting the fish community structure in the reservoirs built on the intermittent rivers of India. We hypothesized that the environmental factors most likely influenced the patterns in the structure of fish diversity at temporal and spatial scales in a subtropical reservoir of the Ganga River basin. The data was gathered seasonally from April 2017 to March 2018 from three sites each in the riverine, transitional, and lacustrine zones of the reservoir. About 16,220 fish specimens were captured that belonged to 7 orders, 14 families, 31 genera, and 40 species. The diversity indices showed the highest diversity in the riverine and the lowest in the lacustrine zones of the reservoir. At a temporal scale, the highest diversity was observed in the monsoon season and lowest during the summer season. The cluster analysis spatially separated the fish fauna into three groups, each group formed by sampling sites in the riverine, transitional and lacustrine regions of the reservoir and may have resulted from physico-chemical and anthropogenic influences. Our study suggests the need to consider the possible influence of altered environmental conditions on fish assemblage, and some recommendations were suggested for the improvement of the fisheries impacted by the construction of dams.

The present study evaluated the effectiveness of stocking the Gangetic carps, viz. Labeo catla, Labeo rohita, and Cirrhinus mrigala, in a large tropical reservoir, Uttar Pradesh, India. Time series data of 22 years (1998 to 2019) on fingerling stocking and fish harvest were collected from the State Department of Fisheries, Govt of Uttar Pradesh. The average annual stocking was 36 nos.ha−1 yr−1, and the fingerling stocking size was ranged between 10 and 90 mm total length (TL) with a mean of 30 mm TL. The average fish production potential of the reservoir was estimated at 77.15 kg ha−1 yr−1. The analysis revealed that fish yield from the reservoir progressively increased from 75.02 t to 297.39 t with a mean of 148.82 ± 69.45 t. The regression analysis between the stocking density and yield of stocked species showed an insignificant relation in the reservoir (R2 = 0.0873, p = 0.2495). The percentage change in the production of stocked species in comparison with the previous year was found to be negative for 12 years between 1998 and 2019 indicated an unstable trend. The finding indicated that low stocking density, very small size at stocking, the low conversion efficiency of the photosynthetic energy to fish (0.016%), and the dominance of catfishes were the major causes for the low fish productivity. We suggest greater stocking density of 500 fingerlings ha−1 yr−1, stocking of fingerlings (> 100 mm TL), in situ breeding and rearing in cages and pens, adoption of cage culture technology, and identification and conservation of the breeding ground of the Gangetic carps to optimize the management regime in utilizing the production potential of reservoirs vis-a-vis ensuring livelihood security and sustainability of the fishers.

AbstractThe river Ganga originates from Gangotri and travels approximate 1,300 km to Vindhyachal, bypassing through a series of dams. Water quality parameters including temperature, pH, dissolved oxygen, alkalinity, chloride, biological oxygen demand, dissolved organic matter, and nutrients were studied from various centers of the river Ganga from Gangotri to Vindhyachal (24 centers). Specific conductivity increased gradually from Maneri above barrage area and reached maximum at Kanpur as the river receives industrial and domestic effluents near Kanpur. Allahabad, Haridwar, and Vindhyachal sampling points were found to be affected by anthropogenic influences. A chloride as well as Myxophyceae were maximum at Kanpur, which indicated that maximum organic pollution at Kanpur plankton population and composition were much more affected by temperature and nutrients than by the construction of dams. However, the pattern of release of water affected the accumulation of nutrients in surface water, which impacted the quality of planktonic fauna and flora. The upper stretch was dominated by diatoms and the middle stretch by green and blue‐green algae as the accumulation of nutrients exhibited eutrophic conditions. Near the source, diatoms like Eunotia, Achanthes, Cymbella, Diatoma, Tabellaria were found to be dominant but as river moves toward downstream, species of Synedra, Melosira, Nitzchia, and Cyclotella became abundant. The study revealed how water quality deteriorated by the construction of each dam. Therefore, when making policy for a dam on any river it is important to maintain at least one stream of the original water flow. The whole river should not be blocked at any point/place or at least 50% of original water should flow continuously to sustain the biodiversity and quality of water, otherwise after traveling a few kilometers through dams, a river will lose its originality.

Phytoplankton species composition and diversity and its relation to physico-chemical parameters were studied in Jargo Reservoir located on River Jargo, a tributary of River Ganga basin, India. A total of 137 phytoplankton species belonging to 8 divisions were recorded indicating rich phytoplankton diversity in the North Indian reservoir. Bacillariophyta contributed the highest number of species followed by Chlorophyta. Filamentous algae such as Geitlerinema sp., Pseudoanabaena sp., Oscillatoria sp. and Phormidium sp. were highly abundant. The contribution of the top ten species ranged between 63% and 98% of total phytoplankton density. PCA analysis of physico-chemical revealed six principal components (HCO 3 , TDS, BOD, DOM, air temperature and pH) which significantly affected the succession of phytoplankton in Jargo Reservoir. The CCA analysis of phytoplankton species and physico-chemical parameters revealed that Ochrophyta and Miozoa were highly influenced by high CO 2 and PO 4 . Higher phytoplankton diversity and species richness were observed during the late winter season and rainy season, respectively. Our investigation recommends that fish production in the reservoir could be enhanced by stocking with fingerlings of silver carp, which has the potential to utilise the unconsumed population of abundant Myxophyta.

The Ganga is the fifth largest river in the world, which drains about 1,060,000 km2 geographical areas (Welcomme, 1985) in India and neighbouring countries. The river traverses through varied catchments consisting glacial no-vegetation zone, alpine and broad leaved forests, meadows, agricultural fields, high density human settlements and industrial developments. The altitudinal and geographical variation, vast and varied catchments, vegetation cover, substratum and influx of numerous tributaries of the river have given rise to varying substratum conditions and micro-habitats in the river. As a result, the river system is reported to harbor about fish 265 species (Sinha, 2006) including coldwater, warm water and estuarine fishes.

Environmental flow of the river Sone at Indrapuri barrage was estimated using 36 years discharge data and the Global Environmental Flow Calculator Software. To maintain the river in moderate condition and to keep basic ecosystem functions intact, at least 18.9% of mean annual runoff (MAR) has been estimated, while the actual discharge of the river was merely 5.16% of MAR. The river presently holds 89 fish species, but 20 species reported in an earlier study were not observed, while 14 new fish species were encountered. Sediments, water and macro-benthic biota of the river were also studied to know the effect of low discharge.