The majestic River Ganga is a sacred environment which nurtures more than 650 million people in her large watershed. The Ganga has proved resilient despite the multiple, enormous, environmental stressors placed on her. The Laurentian Great Lakes have also faced severe environmental degradation and the lessons learned there over the past 50 years can provide guidance for the remediation and restoration of the Ganga. One of the more important lessons is defining Beneficial Use Impairments to focus remediation efforts in degraded Areas of Concern. This paper provides a case study of one such impairment, Eutrophication or Undesirable Algae, and shows how it can be applied as part of a broader Ecosystem Approach towards the identification and selection of Ganga Areas of Concern. The 10 proposed Ganga Areas of Concern are intended to provide guidance to all stakeholders on how and where to focus remediation efforts on the Ganga, and similar ecosystems throughout the world.

The wild stock of Indian major carps is declining in major rivers of India due to pollution, overexploitation, and inbreeding depression. In the present study, the comparative population structure, genetic diversity, and historical demographics of IMCs, Labeo rohita, Labeo catla, and Cirrhinus mrigala were characterized by analyzing partial 307bp sequences of Cytochrome b gene of 357 individuals collected from seven geographically isolated sites from Indian river basins and two culture zones. The DNA sequences alignment among three species revealed comparative divergence and evolution in these heterogeneous species in terms of over transition to transversion ratio of 6.25. The study implicated the occurrence of 35 haplotypes with haplotype diversity of 0.7333 in L. rohita at Brahmaputra basin showing allelic richness, while no nucleotide diversity (π) 0.000 was observed in L. catla of two geographically isolated locations of Rivers Ganga and Narmada. The analysis of molecular variance (AMOVA) revealed the genetic diversity of IMCs is to be very low (9.40%) within the species, as compared to among the three species (80.76%). The Fst scores ranged between 0.000 and 0.996, indicating low to high genetic structure of IMCs. The Haplotype-1, Haplotype-13, and Haplotype-19 in L. rohita, L. catla, and C. mrigala were considered as ancestral haplotypes, respectively. The expansion factor was found to be 0.45000 and 0.90000 for L. rohita stocks at Farakka-Ganga and Allahabad-Ganga, respectively. The present study provides the first report on genealogical biogeography, evolutionary divergence, and expansion of three IMCs, which could help to formulate the strategies for conservation of fisheries biodiversity in the Indian riverine ecosystems.

India has a vast network of 14 major rivers and their tributaries, covering 83% of the drainage basin and accounting for 85% of the surface flow. Anthropogenic activities like damming, channel modification, water abstraction, sewage and effluent disposal, sand mining, unthoughtful exploitation of biotic resources, etc. are the major threats faced by the rivers in the country. Monitoring protocol of Indian rivers lacks an integrated approach based on judicious use of both abiotic and biotic components as well as a total lack of consideration for ecological health. Index of Biotic Integrity is a flexible multimetric index that can be modified and adapted to the various zoogeographic regions of the world. A fish-based multi-metric IBI was developed by modifying and incorporating metrics that are sensitive to the various ecological stressors faced by Indian rivers, fishes being excellent indicators of river health. The adapted IBI was validated and used to assess ecological health of two rivers—Mahanadi, and its distributary Kathajodi-Devi—flowing through central-eastern India. The study indicated that in River Mahanadi, around 25% of the freshwater river stretch was slightly impaired and the remaining 75% stretch was moderately impaired. In Kathajodi-Devi, most of the river stretches were in a moderately impaired condition, except at Italnga stretch where the river was severely impaired. The Index of Biotic Integrity scores estimated could reflect the ecological health of the rivers. The study shows that use of Index of Biotic Integrity is a useful and reliable approach to assess the health conditions of Indian aquatic resources warranting initiatives to be taken to implement and incorporate it into the country's water resource management.

The fishery and population dynamics of Otolithoides pama (Hamilton, 1822) were studied from the Hooghly-Matlah estuary of West Bengal from November 2016 to April 2018. The average annual catch of sciaenids for the last five years was estimated at 22 mt and formed 12.66% of the total marine production of the state of West Bengal, India. The peak landings of O. pama were found during March from gill net catches and November–December from bag net catches. The species followed continuous recruitment throughout the year with two distinct peaks during March–August and July–October. The probability of capture was estimated to be 148.35 mm, while the length at recruitment was 104.5 mm. The rate of exploitation (0.73) was found to be higher than E_max (0.58), indicating a higher fishing pressure of the species. The length-based Virtual Population Analysis revealed that the highest fishing mortality occurred from the 140–159 mm length group onwards. Both Beverton and Holt yield per recruit analysis and Thompson and Bell prediction analysis revealed higher fishing effort being employed for the species, which would need to be reduced by 20% for sustainable management of the species at the studied estuarine system.

Tenualosa ilisha, commonly called Hilsa, is a highly prized species, which has declined in River Brahmaputra, India. The study was carried out for one year and a total of 1,026 individuals were sampled at monthly intervals. In the study, the following growth parameters were observed: asymptotic length (L∞) = 445 mm, growth coefficient (K) = 0.5 year^-1, and age at length zero (t₀) = -0.5 year^-1. Growth performance index (φ) was estimated to be 2.996. Natural mortality rate, total mortality, and fishing mortality was found to be 0.51 year^-1, 1.57 year^-1, and 1.06 year^-1,respectively. Exploitation ratio (E) was found to be 0.675, which indicates that the species is slightly over-exploited. It was seen that length groups that represented the catch in the Indian part of River Brahmaputra comprised fishes of 0–4+ years age. The present study was carried out to assess the population characteristics of this commercially important species from the Indian part of Brahmaputra River, which will contribute towards sustainable fisheries management.

A comprehensive study on the fish assemblages of the River Cauvery was conducted during 2017–2020 by structured fish sampling surveys, encompassing various sampling sites situated along the upper, middle, lower, and estuarine stretches. The present study recorded a total of 146 fish species belonging to 52 families from the River Cauvery. The highest recorded fish diversity was at Hogenakkal (76 species) as it is situated in the transition zone between Deccan Plateau and the plains of Tamil Nadu. Lowest diversity was recorded at Bhagamandala (23 species), as this site represented a narrow hillstream habitat. As per SIMPER analysis, the silver razor-belly minnow (Salmostoma acinaces) was the most representative species in Upper Cauvery, with percentage similarity contribution (% SC) of 36.55%. The Middle Cauvery situated in the plateau zone was mainly represented by Labeo calbasu (14.01% SC), the exotic Nile tilapia (Oreochromis niloticus) with 8.45%, and the bagrid catfish Mystus cavasius (5.1%). The exotic species contributed to maximum fish catch and gradually replaced the native fish fauna in Lower Cauvery. The fish fauna of Cauvery Estuary is distinct from other zones with a characteristic fish assemblage represented by the glassy perchlet, Ambassis miops (11.97% SC), Crenimugil buchanani (11.14 %), and Mugil cephalus (6.23 %). Among the fish species recorded during the present study, 29 species were endemic to Western Ghats, of which 10 species were categorized as threatened by the IUCN, including 2 critically endangered (Barbodes bovanicus, and Hemibagrus punctatus), 5 endangered (Dawkinsia arulius, Hypselobarbus curmuca, H. mussullah, H. micropogon, and Nemacheilus pulchellus) and 3 vulnerable species (Hypselobarbus kolus, Hyporhamphus xanthopterus, and Wallago attu). A holistic study on the fish communities of Cauvery along the spatio-temporal scale is imperative to ensure sustainable management for conservation of endemic fish fauna.

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 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.

The Cooperative Science and Monitoring Initiative aims to generate data and information to support environmental management in the Laurentian Great Lakes of North America. On a rotating basis, efforts are focused on each lake every five years. In this study, we developed a state-of-the-art hydrodynamic and ecological modeling framework to aggregate data collected during these initiative years and from other sources, and to simulate lake eutrophication processes in Lake Ontario, with an emphasis on nearshore conditions. Model calibration and validation were based primarily on data from three initiative years (2008, 2013, and 2018). This integrated model provides a framework for data organization, understanding complex lake process interactions, and guiding future data collection. It is designed as a management support tool that can simulate lake responses to changes in loading conditions, such as sensitivity of nearshore water quality to Niagara River phosphorus loads. Its designated aim is to support evaluation of management questions in Lake Ontario by providing quantitative evaluation of the relative benefits of potential nutrient loading abatement strategies to mitigate eutrophication in the nearshore. This framework is also well suited for possible future expansion to address management issues on a whole-lake basis.