Exploring the vulnerability of the coastal wetlands of India to the changing climate and their adaptation strategies.

Changing climate exerts significant pressure on coastal wetland fishery, ecosystems and livelihood at the eco-regional level. In the present study, an indicator and scoring-based vulnerability assessment framework was developed to assess climate change-induced potential impacts and vulnerability of the coastal wetlands through stakeholder perception and primary data collection on ecology and fisheries. The study was conducted in 12 coastal wetlands in the Gangetic estuarine regions of eastern India. Analysis of rainfall, temperature and extreme climatic events was also carried out. The climate variability in the region was analysed and discussed in the context of ecosystem health and sustainability indicators. The results indicated that anthropogenic stress has a greater influence on ecosystem services than climatic stress. However, the nature and degree of vulnerability of fishers to climate change vary with their capacity to adapt to such changes and alternate sources of livelihood. Altogether, 34 fish species were documented, belonging to 11 taxonomic orders, and categorized as per intensity of resilience using selected criteria. Perception-based climate-resilient adaptation strategies have also been discussed. Developing appropriate adaptation policies and implementing climate-resilient practices and management can minimize vulnerability and increase the adaptive capacity of fishers ensuring sustainable livelihood options.

Ecosystem-based fishery enhancement through pen culture of Indian major carp Labeo catla in a tropical floodplain wetland of North Eastern Region, India, during COVID pandemic.

The present study was conducted with the objective of developing ecologically and economically feasible pen culture protocols for Labeo catla as an alternate income source for wetland fishers in the context of the COVID-19 pandemic. Yearlings of L. catla (12.33 ± 1.99 cm mean total length and 26.05 ± 6.57 g mean weight) were reared in HDPE pens (500 m2 area each) at three different stocking densities of 3 (SD3), 6 (SD6) and 9 (SD9) no. m-2 in triplicates. Fishes were fed with floating pelleted feed containing 28% crude protein and 5% crude lipid two times daily at 1.5-3% of body weight. During the culture period, fish grew from 26.05 ± 6.57 to 434.61 ± 30.63 g, 306.13 ± 10.68 g and 221.13 ± 14.92 g, respectively, at stocking densities of 3, 6 and 9 no. m-2 respectively. Weight gain percentage and specific growth rate declined with increase in stocking density. Gross fish yield increased with increase in stocking density and was highest at SD9 (657.92 ± 53.55 kg pen-1), while net fish yield increased initially from SD3 to SD6 (594.31 ± 29.72 kg pen-1) and then declined with further increase in stocking density. Important water quality parameters influencing fish growth were measured, and significant difference (p > 0.05) was not observed between treatments (inside pens) and reference site (outside pen at 10-m distance). Weight gain was positively correlated (p < 0.05) to water temperature (r = 0.989) and total phosphorus (r = 0.81). Benefit cost ratio and net return was highest at SD3 (1.61; US $518.88, respectively). Stocking density of 3 no. m-2 can be considered economically feasible for table fish production of L. catla in pens. Post pen culture, monthly income of fishers increased by 10.76-179.11%, with a mean increase of 90.57%, compared to the period of first COVID-19 wave in India. The present findings can provide an impetus for effective utilization of pen enclosures for income generation and livelihood enhancement of small-scale wetland fishers during pandemic.

Influence of stocking density and environmental factors on the expression of insulin-like growth factors in cage-reared butter catfish (Ompok bimaculatus, Bloch 1794) within a large reservoir ecosystem.

In vertebrates, insulin-like growth like factors (IGFs) play an important role in growth and other physiological processes. The GH-IGF axis is considered a valuable tool to monitor fish growth performance. Herein, we report the molecular characterization of igf-1, igf-2, and ß-actin transcripts and relative expression of igf-1 and igf-2 in the liver and muscle tissue of cage-reared butter catfish, Ompok bimaculatus, in response to different stocking densities (T1, 15 fingerlings m-3; T2, 25 fingerlings m-3; and T3, 35 fingerlings m-3) over 180 days of culture duration. The length of the partial amplified transcript sequence of Obigf-1, Obigf-2, and Obß-actin was 325, 438, and 924 bp, respectively. Phylogenetically, Obigf-1 and Obigf-2 were closely clustered with catfishes, viz., Clarias magur, Bagarius yarrelli, and Silurus asotus. The expression of igf-1 was significantly downregulated in the liver at higher densities after 120 days as biomass in the cages increased, while igf-2 expression did not change with the stocking densities over the culture period. Cortisol concentration was significantly elevated in T3 groups post 150 days of the culture period and correlated negatively with the expression of igf-1 (p < 0.05) and igf-2 (p > 0.05). Environmental parameters, pH, TDS, hardness, conductivity, and alkalinity showed a significant positive correlation with hepatic IGF expression. Our study indicates that the liver-derived igf-1 plays a more important role in the regulation of growth in response to culture density in the species studied, and thus, igf-1 can be used effectively as a biomarker for growth. Furthermore, this study will help in planning a proper harvest schedule and optimize the culture practices of O. bimaculatus in an open water cage system.

Exploring fish assemblage structure, feeding guild, and water quality in a typical river-reservoir interface of tropical large reservoir environment, Central India.

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%, Schistura dayi (3.71%), and Rita pavimentata (3.41%) of dissimilarity among Maheshwar (S1), Rajghat (S2), Koteshwar (S3) non-confluence zone, and Kakrana (S4)-confluence zone. The analysis of data indicated disappearance of some species like deccan peninsular carp Labeo fimbriatus, Mahseer Tor khudree which was earlier reported but was absent in recent years. The statistical correlation of environmental variables with observed abundances of fish feeding guilds showed significant positive correlation with specific conductivity and total dissolved solid content of the water. The canonical correspondence analysis (CCA) indicated association among omnivorous fishes of the reservoir with water temperature; total dissolved solids; specific conductivity; total alkalinity; chlorophyll; and NO3-N. The herbivore fishes were found to be more associated with magnesium, dissolved oxygen, and phosphorus content of the water while insectivorous fishes were more associated with the silicate and transparency of the water. The abundance of omnivores species indicated dominance of generalist fish species rather than specialists in the interface region of reservoir showing conservation and ecological importance of the ecosystem. The baseline information generated on fish assemblage and ecological perspectives of the river reservoir interface and science-based management recommendations formulated in the study are critical for sustaining fish diversity, promoting fisheries enhancement, and management planning of tropical large reservoirs.

Combining stakeholder perception and ecological approaches for assessing vulnerability of floodplain wetlands in changing climate: a regional study.

Wetland fisheries are most vulnerable to climate and anthropogenic change, and therefore, vulnerability assessment is essential for the formulation of prudent management strategies. In the present study, vulnerability assessment was carried out in nine floodplain wetlands from three districts of West Bengal using stakeholder perception and ecological conditions. In absence of long-term time series data on ecology and fisheries of wetlands, stakeholder perception study was carried out to assess the vulnerability status to climate change. Phased interviews were conducted using structured questionnaires to study the stakeholder perception on climatic variability and changes in ecology and fisheries of wetlands over the past 15 years. Climate data used for climate trend analysis was procured from Indian Meteorological Department. Ecological parameters were studied from the wetlands seasonally from January 2018 to December 2018. Analysis of climatic variables for last three decades revealed a warming trend and decreasing rainfall in the study area. The temperature anomaly ranged from + 0.07 to + 0.31 °C while rainfall anomaly ranged from - 61.41 to - 372.62 mm. Respondents showed high level of consensus (75.3%) on climate change awareness. The respondents were aware of the fact that climate anomaly affects ecology and fisheries of wetlands in most of the cases with consensus ranging from 67.8 to 94.7%. The studied wetlands showed 2 to 81.28% reduction in depth, 21.52-61.29% reduction in species diversity, and 30-95% macrophyte infestation. The stakeholder perception-based vulnerability scores ranged from 18 to 31 and indicated 6 out of 9 wetlands (66.6%) as highly vulnerable and the rest as moderately vulnerable. The ecological vulnerability scores ranged from 17 to 21 and indicated 5 out of 9 wetlands (55.6%) as highly vulnerable and 4 wetlands in the moderately vulnerable range. Although both the approaches used in the present study categorized the studied wetlands as moderately to highly vulnerable, the category of some of the wetlands varied in both the approaches. This suggests that utilizing a single approach may not give precise vulnerability status of an ecosystem. Use of combined approaches for construction of a composite vulnerability index covering different aspects impacted by climate change might present a better picture of the vulnerability status and aid in formulation of effective mitigation/management plan.

Dietary arginine attenuates hypoxia- induced HIF expression, metabolic responses and oxidative stress in Indian Major Carp, Cirrhinus mrigala.

Hypoxia is a common stressor in aquaculture systems, which causes severe physiological disturbances, ultimately leading to mortality or reduced productivity. Arginine, as a precursor of NO, has a role in enhancing oxygen delivery. Thus, an experiment was conducted to evaluate the effect of dietary arginine (Arg) in Cirrhinus mrigala exposed to hypoxia. The fish were fed with different levels of arginine for 60 days and exposed for 72 h to a sublethal level of hypoxia (0.50 ± 0.16 mg/L dissolved oxygen [DO]). The six treatment groups with three replicates were N0 (0% Arg + Normoxia), H0 (0% Arg + Hypoxia), N0.7 (0.70% Arg + Normoxia), H0.7 (0.70% Arg + Hypoxia), N1.4 (1.40% Arg + Normoxia), H1.4 (1.40% Arg + Hypoxia). Eighteen experimental units with twelve animals (5.8 ± 0.18 g) each were used for the trial.The results indicated that supplementation of arginine at 0.7 and 1.4% enhanced the hypoxia tolerance time, although the high dose (1.4%) did not yield any further increments. The exposure to hypoxia up-regulated Hypoxia Inducible Factor (HIF)-1α mRNA expression and supplementation of arginine significantly decreased hypoxia induced up-regulation of HIF at 1.4%. Arginine supplementation partially or completely normalised the hypoxia induced changes in the metabolic enzymes of C. mrigala. The fish exposed to hypoxic conditions exhibited significantly higher (P < 0.05) lipid peroxidation levels than those maintained under normoxic conditions, while arginine feeding significant in reducing lipid peroxidation. Antioxidant enzyme activities were significantly higher (P < 0.05) in hypoxia-exposed carp, indicating increased oxidative stress during the hypoxic exposure, that was improved in Arg-supplemented groups. However, arginine did not modulate erythrocyte countsalthough itreduced the erythrocyte fragility. We conclude arginine supplementation is effective in ameliorating hypoxia induced metabolic alterations and improving antioxidant defences in fish.

Inland heat waves (IHWs) and associated impacts on hydro-biology of aquatic ecosystems in lower Ganga basin, India.

The present study assessed the occurrence and impact of heat waves on the ecology of two ecosystems namely Bhomra wetland and Ganga River stretch, India. The water samples collected from these ecosystems were analyzed for estimating the hydrological and biological variables during heat wave. The inland heat index (IHI) was derived from the climatic variables, relative humidity and temperature. The study indicated the predominant and periodic occurrence of inland heat waves (IHW) with indices ranging from 34.8 to 42.8 °C and 35.9 to 43.5 °C at the Bhomra and Ganga River stretch respectively during the summer months (March-June). The first two components of the principal component analysis of physico-chemical parameters and heat index explained 45.6% and 59% of the variation in the Bhomra and Ganga River stretch respectively. PCA showed a similar pattern in variation of IHWs and dissolved oxygen, nutrients, hardness and alkalinity, but a distinct pattern with conductivity and TDS in the wetland. IHW exhibited a similar pattern of variation with TDS, conductivity, dissolved oxygen, pH and hardness and distinct pattern with alkalinity, phosphate and nitrate in the river stretch. The first two components of PCA of IHI and plankton abundance explained 89% of the variation and IHI had a similar pattern of variation with the abundance of diatoms and a diverse pattern of variation with blue-green and green algae in the studied ecosystems which might affect the food availability of the associated fishes. The study suggests that IHW influences the water quality and primary producers and also summarizes the impact of IHW on ecosystem services and necessitates mitigation measures.

Dynamics of phytoplankton community in seasonally open and closed wetlands in the Teesta-Torsa basin, India, and management implications for sustainable utilization.

The present study deals with the broader understanding of phytoplankton assemblage pattern and their ecohydrological interactions in two ecologically distinct floodplain wetlands of Teesta - Torsa basin, India. Analyses of data revealed significant seasonal variations (p ≤ 0.05) of ten water variables (temperature, transparency, pH, conductivity, total dissolved solids, dissolved oxygen, total hardness, total alkalinity, PO4 - P, and SiO4 - Si) in both the wetlands; however, no significant variation was observed among the sampling stations. In total, 128 species of phytoplankton were recorded (118 species belonging to 94 genera in seasonally open; 103 species belonging to 86 genera in closed wetland). Four algal groups, viz. Cyanophyceae, Coscinodiscophyceae, Bacillariophyceae, and Chlorophyceae, were the dominant quantitative component, remarkably influencing the total phytoplankton population in both the wetlands, contributing ~ 87% of total phytoplankton. Species Aulacoseira granulata alone contributed 12 - 41% and 8 - 34% to the total phytoplankton in the seasonally open and closed wetland, respectively, and indicated high organic load in both the wetlands. Altogether thirty-six and thirty-one phytoplankton taxa appeared as major indicators across the seasons for seasonally open and closed wetland, respectively. The indicator taxa (Aulacoseira, Oscillatoria, Dolichospermum, Spirogyra, Synedra, Nitzschia, Navicula, Euglena, Phacus) in both the wetlands hinted that the wetlands are under pollution pressure. The assemblage structure of phytoplankton was related to transparency, NO3 - N, PO4 - P, SiO4 - Si, total dissolved solids, and temperature as evident from BIO - ENV. Furthermore, the marginal test also selected similar variables (depth, transparency, conductivity, PO4 - P, SiO4 - Si) for seasonally open and the variables such as depth, conductivity, total dissolved solids, total alkalinity, and NO3 - N for the closed wetland. The study showed that the seasonal riverine connectivity greatly influences the variations in phytoplankton community in the seasonally open wetland.

Environmental parameters and stocking density influence growth, feed utilization and economics of butter catfish, Ompok bimaculatus (Bloch, 1794) production in floating net cages in a large tropical reservoir, India.

An experiment was conducted to study the influence of environmental parameters and stocking density on growth, survival, feed utilization, and economic feasibility of a high value butter catfish, Ompok bimaculatus in floating cages in a large tropical reservoir of India for 180 days. The fingerlings (11.44 ± 1.33 cm; 8.05 ± 3.27 g) were stocked at three stocking densities, viz., 15, 25 and 35 fingerlings m-3 in GI cages (32m3) in triplicates. Commercial floating pellets were fed to fish at 5-3% of fish biomass. The results indicated that the fishes at the lowest stocking density of 15 fingerlings m-3 had significantly higher (p < 0.05) growth in relation to weight gain percentage (717.67 ± 39.10) and specific growth rate (1.14 ± 0.05). Survival percentage was also significantly higher (p < 0.01) at lower stocking densities compared with 35 fingerlings m-3. Similarly, the feed conversion efficiency (0.423 ± 0.025), protein efficiency ratio (1.37 ± 0.15) and feed conversion ratio (FCR) (2.37 ± 0.16) were significantly better at density of 15 fingerlings m-3. The fish growth and feed utilization efficiency did not vary significantly (p > 0.05) between stocking densities of 15 fingerlings m-3 and 25 fingerlings m-3. The condition factor was insignificantly higher at lower densities and its values close to 1 indicated congeniality of reservoir ecosystem for cage culture of the species. The coefficient of variation of weight was significantly higher (24.19 ± 1.20) at 35 fingerlings m-3. The highest economic gains in terms of benefit cost ratio (1.77) were achieved at the lowest stocking density. The present study indicated better growth and economic returns at lower stocking densities of 15-25 fingerlings m-3. The nutrient load and plankton abundance were higher at culture site, however, did not vary significantly from reference sites throughout the culture period. Although most of the environmental parameters showed significant seasonal variations, dissolved oxygen showed significant positive relation (r = 0.86) with the growth of the fish. This is the first study reporting feasibility of cage culture of this highly renumerative species in open waters. The cage culture of this species will not only ensure better economic returns to the marginal cage farmers but will aid in the conservation of this species in natural ecosystem. Being a low volume high value species, the impact on environment will be less compared with high volume low value species. This study will serve as baseline for standardization of its grow-out protocol in cages and will be a step towards much needed species diversification for sustainable small scale cage farming in tropical reservoirs of Asia.

Reproductive environment of the decreasing Indian river shad in Asian inland waters: disentangling the climate change and indiscriminative fishing threats.

The regional climate has significantly warmed with erratically declining annual rainfall and intensified downpour within a narrower span of monsoon months, which led to an increased trophic state (≈algae) in most inland waters. Freshwater clupeids vitally control the aquatic food chain by grazing on algae. Despite increasing food availability, IUCN Red List® revealed 16 freshwater clupeids with a decreasing population trend. We investigated one such species' reproductive dependencies, Gudusia chapra (Indian river shad), in the lower Gangetic drainage (India) under a mixed context of climate change and overfishing. Monthly rainfall (≥ 60-100 mm) and water temperature (≥ 31-32 °C) are key breeding cues for females. The regional climate seems inclined to fulfill these through the significant part of the breeding season, and indeed the species has maintained consistent breeding phenology over 20 years. Other breeding thresholds relevant to fishing include size at first maturity (≥ 6.8 cm; reduced by ~ 25-36%) and pre-spawning girth (Girthspawn50 ≥ 7 cm; first record). Girthspawn50 is a proxy of the minimum mesh size requirement of fishing nets to allow safe passage of "gravid" females (+ 22% bulged abdomen) and breed. The operational fishing nets (3-10 cm mesh) probably have been indulged in indiscriminative fishing of gravid females for generations. Under a favorably changing climate and food availability, existing evidence suggests a fishery-induced evolution in regional females (to circumvent such mesh sizes) through earlier maturation/puberty at smaller sizes. It could be an early warning sign of population collapse (smaller females → lessening fecundity → fewer offspring). Overfishing seemed to be a bigger threat than climate change.

Food selectivity and reproductive biology of small indigenous fish Indian river shad, Gudusia chapra (Hamilton, 1822) in a large tropical reservoir.

Assessment of life history strategies of economically important small indigenous fishes (SIF) which are rich in nutritive values is essential and imperative to artisanal and subsistence small-scale inland fisheries of Indian tropical reservoirs. The present investigation aims to estimate the food selectivity in juveniles and adults, reproductive traits such as sexual maturity, gonadosomatic index, ova diameter, and fecundity of Gudusia chapra from a large impounded ecosystem of India. A total of 668 (Juvenile 129, adult 539) specimens, 37 to 142 mm standard length and 0.89-25.68 g body weight were collected during October 2014-September 2015. The qualitative estimation of the stomach contents revealed herbi-omnivorous feeding behavior of fish. The mean relative gut length (mRGL) of the species was 1.557 ± 0.024 in juveniles and 1.154 ± 0.012 in adults. The sex ratio was 1:1.30 with dominance of females in the population though insignificant. The total length at which 50% individual attain maturity (TL50) was estimated as 80.50 mm based on the logistic curve. The absolute fecundity of the individuals ranged from 749 to15044, and ova diameter ranged from 0.10-2.00 mm. The gonadal indices (GSI, MGSI, and DI) indicated that spawning extended throughout the year with peak reproductive activity in October, March-April, and July (mean absolute fecundity ranged from 4000 to 6000). The present study characterized biological and reproductive traits of G. chapra from a large reservoir ecosystem and demonstrated a new trend of reproductive pattern which will serve as benchmark data for future assessment and management planning of this species in impounded waters. The study also suggested some specific management measures for sustainable exploitation and conservation of small indigenous species.

Studies on the growth and mortality of Indian River shad, Gudusia chapra (Hamilton, 1822) from Panchet reservoir, India.

The Indian river shad, Gudusia chapra (Hamilton, 1822), is a commercially important freshwater clupeid that contribute to the livelihood of subsistence and marginal fisheries in inland open waters of India and its adjacent countries. The present study was carried out on the growth and mortality of Indian River shad, Gudusia chapra (Hamilton, 1822) based on the commercial length-frequency data collected monthly during October 2014 to September 2015 of a large reservoir located in the border of Jharkhand and West Bengal. The ELEFAN-I (Electronic Length Frequency Analysis) module in FiSAT (FAO-ICLARM Stock Assessment Tools) was used for estimation of growth parameters (L∞, K). The total mortality was estimated following Pauly (ICLARM Fishbyte 2(1):9-13, Pauly 1983) whereas exploitation ratio and maximum sustainable yield were calculated following Gulland (1979). The asymptotic length (L∞) and growth coefficient (K) were estimated as 194 mm and 1.23 year-1, respectively. The species grows to 141.56 and 182.91 mm at the end of the 1st and 2nd years of life. The total natural and fishing mortalities were 6.63, 2.45 and 4.18 year-1 respectively. The value of growth performance index was 2.69. The exploitation ratio (E) was estimated as 0.63. As the exploitation ratio (E) is slightly beyond the optimum, there is likelihood of some threat of overexploitation. Though recruitment was continuous, major pulse was observed during April-May. The present investigation is a first report from Indian reservoir. The maximum sustainable yield of this species was estimated as 485.6 t against the present annual yield of 612.3 t. Avoiding overfishing and wise use of available resources are of prime importance for sustainable fishery management of the reservoir.