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Information on various aspects of reproductive traits of female pool barbs from various stretches of Ganga River basin, India was generated in relation to climatic variability. The presumptions surrounding – minnows being the first and easily hit by climatic variability, was validated. GAM models revealed low threshold rainfall requirement (>50 mm) within a wide temperature range (20–30 °C) necessary for attainment of breeding GSI (>10.5 units). Pre-spawning fitness (Kspawn50) and size at 50% maturity (LM50) benchmarked through Kaplan-Meier survival estimates were in the range 1.61–1.67 units (Fulton condition factor) and 8.6–9.0 cm respectively. Mapping of climate preferendum through LOESS smoothing hinted both low-mild rainfall (50–150 mm) and high rainfall conditions (400–700 mm) conducive for attaining pre-spawning fitness while no dependence on temperature was observed. First maturity of females was encountered at 4.7 cm within the size range 4.4–12.6 cm. The present study hinted a probable reduction (1.4–1.8 cm) in size at maturity of female pool barbs. We observed pool barbs can breed within a wide thermal regime following slightest of rainfall events. Collating this with the present rates of climatic variability, we infer negligible threat of changing climate on reproduction of Puntius sophore in near future – contrary to the existing presumptions. Owing to the easiness in attainment of pre-spawning fitness under an apparently flexible climate preferendum, ‘skipped spawning’ decisions while facing climatic variability also seem minimum. The recorded breeding thresholds may serve as future references while assessing climate driven changes on reproduction and evolutionary adaptations in Gangetic minnows.

The main objectives of the present study were to quantify the environmental, especially temperature and rainfall, effects on breeding phenology of selected catfish species and to predict changes in breeding phenology of the selected species in relation to climatic variability for the Ganga River Basin. The study showed that changes in rainfall pattern may have the most profound effect on gonad maturation and breeding of Mystus tengara and Mystus cavasius followed by the effect of increased water temperature due to rising air temperature. Indication of region-specific adaptation was noticed in reproductive phenology of Eutropiichthys vacha based on local trends of warming climate. The other habitat parameters, such as dissolved oxygen, alkalinity, nitrate, and phosphate, were correlated with gonad maturity and spawning. Climatic variability may bring region-specific changes in breeding phenology of fish species in the Ganga River. Under a warming climate, changes in precipitation pattern manifested into riverine flow pulse may be the key driver in dictating breeding phenology. Our study indicates E. vacha as a climate sensitive species that may be selected as a target species for climate change impact studies.

Wetlands are considered as one of the most effective carbon (C) sink among various ecosystems. To substantiate this view, the present investigation was conducted in one of the units of sewage fed East Kolkata wetlands (EKW), a Ramsar site, over a period of 3 years. The result revealed that because of high primary productivity due to abundance of primary producers and other sources of C input primarily through sewage influx, there is net positive balance of C in the system. The rate of C accumulation estimated through C budget was 1245.27–2490.55 kg C ha−1 year−1 while the rate estimated through sediment core analysis came out to be 1584 kg C ha−1 year−1. The amount of total C deposited up to 15 cm depth in sediment was 29.37 Mg ha−1, quite higher than the C deposited up to 15 cm depth of reference upland soil which was measured at 23.79 Mg ha−1. If C burial from this experiment in 55 ha is up-scaled for entire EKW of 12,500 ha area, then it empirically corresponds to 56.97–113.94 Gg CO2 captured from atmosphere per annum. EKW is not only used for aquaculture production thereby harvesting blue carbon but also has great potential to accumulate C in its sediments and thus helping mitigate climate change.

Floodplain wetlands are considered as biologically sensitive habitats and predicted to be the most impacted through climate change. They form an important fishery resource in West Bengal, India. Analysis of Indian Meteorological Department (IMD) derived climatic data has revealed a unanimous warming trend (0.18–0.28 °C) and decreasing rainfall (135.6–257 mm) among the studied districts (North 24 Parganas, Nadia and Kolkata) of West Bengal over the last three decades. Four floodplain wetlands under cooperative fisheries management were studied during February 2015 and December 2015. Data were collected through a structured communication process involving multiple interviews through multiple rounds of surveys and also from secondary sources. Six climate smart fishery strategies could be identified, namely Temporary pre-summer enclosure, Submerged branch pile (Kata) refuge, Autumn stocking, Torch light fishing, Deep pool (Komor) refuge and Floating aquatic macrophyte refuge fishery (Pana chapa). Few of them are capable of serving as conservation tools by providing refuge during summer or water stress and maintaining base stocks in the wetlands for recruitment in the following monsoon season. The present paper discusses the climate smart nature of these pre-existing indigenous fishery strategies. These strategies need to be optimized and may be used for adoption of sustainable climate smart fisheries management in floodplain wetlands.

Temperature and seasonal rainfall along with other environmental variables are important in regulating the reproductive cycles in teleost fishes. Certain environmental variables may act as cues for reproduction and changes in these may affect seasonality and success of reproduction, as fishes are known to integrate their physiological functions with environmental cycles. Wetlands are sensitive to climate change due to their shallow and confined nature. Since wetlands are important spawning and nursery grounds for many fishes, changes in the environmental variables may have direct consequences for the spawning and survival of fish. In the present study, we have assessed climatic and water chemistry variables capable of influencing seasonality in environmental variables as well as gonadal maturation of spotted snakehead Channa punctata, to predict threshold values of Gonado Somatic Index in females and a favourable range of identified climatic and water chemistry variables for breeding success. Among the climatic and water chemistry variables studied, seasonal variation in rainfall was found to have the most profound effect on gonadal maturation and breeding in C. punctata, followed by water temperature. The favourable range of rainfall obtained varied between 800 mm to 1400 mm, corresponding to the water temperature range between 29 °C and 31 °C. An overall significant warming trend with a reduction in total rainfall has been observed with changes in seasonal trends in temperature and rainfall in the study area. The rainfall being the major climatic factors influencing water chemistry in the wetlands during the spawning season, changes in rainfall pattern may influence breeding periodicity of C. punctata in wetlands in climate change scenario.

Wetlands are biologically sensitive habitats and envisaged as the most impacted systems by climate change. Floodplain wetlands of West Bengal, India, are important fisheries resources and provide tremendous economic and ecological services. There is lack of long-term quantified data to assess the impacts of climate change on floodplain wetlands fisheries in India. The article presents a stakeholder-driven approach to quantify the impacts of climate change on wetland fisheries. A modified Delphi method has been used to accomplish this. The present article discusses the modified methodology and the results obtained thereof. The study identified around seven potential climate change-induced threats on wetland fisheries among which water stress (95% consensus), wetland accretion/sedimentation (85%), aquatic weed proliferation (70%) and loss of wetland connectivity (65%) are high-priority issues demanding immediate management action. These issues are expected to further aggravate in future climatic scenario.

The concept of threshold condition factor (Fulton), beyond which more than 50% of the female fish population may attain readiness for spawning coined as pre-spawning fitness (K spawn50), has been proposed in the present article and has been estimated by applying the non-parametric Kaplan-Meier method for fitting survival function. A binary coding strategy of gonadal maturity stages was used to classify whether a female fish is “ready to spawn” or not. The proposed K spawn50 has been generated for female Mystus tengara (1.13–1.21 units), M. cavasius (0.846–0.945 units), and Eutropiichthys vacha (0.716–0.799 units). Information on the range of egg parameters (fecundity, egg weight, egg diameter) expected at the pre-spawning stage was also generated. Additional information on species-specific thermal and precipitation window (climate preferendum) within which K spawn50 is attained was also generated through the LOESS smoothing technique. Water temperatures between 31 and 36 °C (M. tengara), 30 and 32 °C (M. cavasius), and 29.5 and 31 °C (E. vacha) and monthly rainfall between 200 and 325 mm (M. tengara), > 250 mm (M. cavasius), and around 50 mm and between 350 and 850 mm (E. vacha) were found to be optimum for attainment of K spawn50. The importance of parameterization and benchmarking of K spawn50 in addition to other conventional reproductive biology parameters has been discussed in the present article. The purposes of the present study were fulfilled by generating baseline information and similar information may be generated for other species replicating the innovative methodology used in this study.

Reproductive biology of female amphidromous croaker Johnius coitor (Hamilton, 1822) was studied for the first time from various freshwater stretches of Ganga river basin, India in relation to climatic variability. The species showed high spatial variation in reproductive phenology and capable of breeding during pre-monsoon, monsoon, post-monsoon and winter. Water temperature is the most crucial environmental parameter influencing gonadal maturation and breeding. Generalized additive model (GAM) models revealed water temperature near 23–25 °C as optimum and threshold GSI above 3 units necessary for breeding. Pre-spawning fitness (Kspawn50) and size at 50% maturity (LM50) benchmarked through Kaplan-Meier survival fit estimates were in the range 1.27–1.37 units and 19–24.5 cm respectively. First maturity of females was encountered at 11.4 cm within the size range 7.2–28.5 cm. Egg parameters in mature-ripe females ranged between 0.29–0.80 mm (diameter), 0.05–0.19 mg (weight) and 5687–121 849 eggs (absolute fecundity). Mapping of climate preferendum through LOESS smoothing technique hinted water temperatures 32 °C to be detrimental for attainment of pre-spawning fitness while no dependence on rainfall was observed. Based on the climato-hydrological influence on breeding and regional trends of changing climate along river Ganga, we infer minimal climate driven changes in breeding phenology of this amphidromous fish species. Results of this study may serve as baseline information for future studies assessing climate driven changes and evolutionary adaptations in croakers from river Ganga.