Perceptible changes on a global and regional scale are evident in earth's climate. In India, observed changes include an increase of air temperature, regional monsoon variation, frequent droughts and a regional increase in severe storm incidence in coastal states of India, along with indication of Himalayan glacier recession. The impact is being felt in the inland aquatic resources and their fisheries. Analysis of time series data of 30 years from published literature and from current investigations on the River Ganga and water bodies in its plains, indicate increased minimum water temperatures; 1.5°C in colder stretches of the Ganga and 0.2 to 1.6°C in the aquaculture farms of the State of West Bengal in the Gangetic plains. Rainfall has also increased in the post monsoon months of September–December. The impact is manifested in the breeding failure of the Indian Major Carps (IMC) and a consequent decline in fish spawn availability in river Ganga. Whereas, in fish farm hatcheries on the plains, a positive impact on breeding was observed in the advancement and extension of the breeding period of IMC by 45–60 days. A geographic shift of warm water fish species Glossogobius gurius and Xenentodon cancila to the colder stretch of the river Ganga was recorded. The predator prey ratio in the middle stretch in the river Ganga has also declined from 1:4.2 to 1:1.4 in the last three decades. Fish production has shown a distinct change in the last two decades in the middle stretch of river Ganga where the contribution of IMC has decreased from 41.4% to 8.3% and that of miscellaneous and catfish species increased. Climate change in India will put an additional stress on ecological and socio-economic systems that are already facing pressure. Thus the specific climate variables of importance to inland fisheries viz. enhanced water temperature, extreme events like flood and drought, storms and water stress require specific adaptation actions. An integrated water shed management strategy is essential going from the village level to the river basin level in a unified manner. Finally, it is suggested that assessments of inland fisheries vulnerability to climate change should also assess economic scenarios since adaptive capacity is closely linked to the financial capabilities.

From March 2001 to December 2003 eight direct count surveys in an upstream direction were conducted for Ganges river dolphins Platanista gangetica gangetica in the Vikramshila Gangetic Dolphin Sanctuary, a c. 60 km long segment of the middle Ganges River in Bihar, India. The mean number of dolphins recorded during upstream surveys was 119.4±SD 31.8 (range 88–174), with an encounter rate of 1.8 dolphins km−1 (range 1.4–2.8). During these surveys a rich diversity of other threatened aquatic wildlife was also documented, including the Indian smooth-coated otter Lutrogale perspicillata, gharial Gavialis gangeticus, a variety of freshwater turtles, and 135 water bird species. An assessment of fisheries documented 76 fish species of which 43% were caught exclusively in monofilament gill nets, a gear known to kill dolphins by entanglement. Eight new records of fishes preyed upon by Ganges river dolphins were identified from the stomach contents of two dolphin carcasses (Setipinna brevifilis, Osteobrama cotio cotio, Puntius sophore, Crosochelius latius, Mystus cavasius, Heteropneustus fossilis, Macrognathus pancalus, Sperata seenghala). These fishes and other species previously recorded in the diet of the dolphins composed 33.3% of the total catch sampled in 2001–2003. Interviews of 108 fishing households revealed that literacy rates were low (29.9%) and almost 50% earned less than USD 411 per year. The most important conservation actions that could be taken are for national and state governments to establish civil control and promote the development of community-based fishing cooperatives. These cooperatives could enjoy ownership rights to certain river segments in exchange for employing sustainable fishing techniques that are less injurious to dolphins.

1.Limited visual perception in aquatic environments has driven the evolution of diverse sensory modalities in aquatic mammals. Dolphins largely use echolocation for prey capture in the face of limited visual and olfactory cues. Multiple foraging modes exist, although an understanding of how sensory systems are adapted to environmental and prey characteristics is limited. This is especially true for animals with extreme sensory specialisation, such as South Asian river dolphins of the genus Platanista. This taxon is effectively blind and retains plesiomorphic traits from its once-diverse ancestors. Distributed in murky rivers of the Indus-Ganga-Brahmaputra basins, it is thought to use mainly echolocation for feeding on fish and shrimp. 2. We hypothesised that foraging modes used by Platanista differ according to prey position in the water column (at the river surface, mid-column, and bottom) and are mediated by ecomorphology, acoustics, prey characteristics, and habitat features. 3. To test this, we combined a detailed review of the literature (anatomy-physiology-morphology studies, observations in captivity) with preliminary field observations and acoustics studies to investigate foraging mode selection. 4. Platanista displays peculiar foraging and feeding behaviours, including side swimming, rotational feeding, and grasp-suction feeding. Feeding is restricted to small prey with low body depth. At the river surface and bottom, echolocation-based foraging may not be efficient due to acoustic reflection or reverberation effects. 5. Platanista uses echolocation clicks to scan and detect prey at distances of about 20 m across the river mid-column, possibly switching to passive listening at the surface, and electroreception at the bottom, to maximise prey capture rate and feeding success. 6. Platanista is remarkable for its ability to persist in some of the most intensively used and abused river basins of the world. Using echolocation, electroreception, and passive listening might reduce overall foraging costs and contribute to the adaptability of the taxon.

Monthly surveys of local fisheries from five principal landing sites on the River Ganges at Bhagalpur, India, were conducted from 2001 to 2007. Fishes of a range of sizes with mostly periodic-type life-history strategies, including many catfishes and carps, dominated the catch. Average annual yield (total mean monthly catch in units of biomass) was highly variable but trended downward during the study. Statistical ordination revealed associations between assemblage composition and hydrological seasons. Overall yields in this reach of the River Ganges tended to be greatest when the annual flood pulse was sustained longer. Patterns of average stock yields and inter-annual variability of yields were associated with species life-history strategies, with the most abundant and least variable species having periodic-type strategies of seasonal spawning, high fecundity, small eggs and no parental care. Although not appearing to have declined precipitously during the study, many stocks in this stretch of the River Ganges, including those of the largest and most valuable species, nonetheless seemed to remain below historical yield levels because of multiple impacts, including chronic intense fishing and other anthropogenic impacts.K E Y W O R D S : assemblage structure, fish community, flood pulse, floodplain, life-history strategy.

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Local ecological knowledge (LEK) can offer insights into fisheries management by describing long‐term changes that are difficult to unravel in data‐poor river‐floodplain fisheries. LEK is derived from complex interactions between fishers’ observations of environmental change and their institutional capacities to manage fisheries. Hence, it is important to understand where and how LEK and formal scientific studies on fish species’ decline could complement each other. In this paper, the causes of decline of 58 fish and two shrimp taxa were identified from LEK data (1999–2019) obtained from river–floodplain fisheries of the Gangetic plains (Bihar, India). Qualitative analyses of LEK were used to generate species‐specific hypotheses and historical insights on their declines. Destructive fishing, overfishing and the Farakka barrage were cited by fishers as the major causes of declines. Potential reasons for these perceptions were explored in relation to fishers’ experiences of conflicts in the region over fishing rights and access.

River-floodplains support a significant number of small-scale capture fisheries despite having undergone degradation due to human modification of river flows by dams, pollution, and climate change. River fish production is underpinned by the annual flood-pulse and associated environmental changes that act as cues for spawning and dispersal for most species. However, studies on fish stock declines have focused more on overfishing than on hydroclimatic variability. Therefore, understanding how changes in flood-pulse variability influence fishing effort and yields is critical to inform adaptive fisheries’ management. We investigated hydroclimatic factors driving flood-pulse variability and fish catch–effort dynamics in India’s Ganga River over two decades (2000–2020). We compiled fishers’ narratives of changing fish catches through semi-structured interviews to compare them with our observed trends. Flood amplitude showed increasing variability, longer duration, and earlier rise timings, linked to La Niña and El Niño phases. Catches per unit effort were correlated with total yield and effort but did not decline as fishers thought, despite overall declines in yield over time. Hydroclimatic variability was a more significant driver of changing yields than local fishing pressure. Rising uncertainty in fisheries’ production, in response to increasing flood-pulse variability and altered flows in the Gangetic Plains, may be affecting fishing behaviour and underlying resource conflicts.

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