Papers by Soma Das Sarkar
International Journal of Biometeorology, 2019
The main objectives of the present study were to quantify the environmental, especially temperatu... more 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.
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Environmental Biology of Fishes, Jan 18, 2018
Temperature and seasonal rainfall along with other environmental variables are important in regul... more 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.
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Aquatic Living Resources, 2018
Reproductive biology of female amphidromous croaker Johnius coitor (Hamilton, 1822) was studied f... more 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 <20 °C and >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.
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The concept of threshold condition factor (Fulton), beyond which more than 50% of the female fish... more 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 (Kspawn50), 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 Kspawn50 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 Kspawn50 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 Kspawn50. The importance of parameterization and benchmarking of Kspawn50 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.
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Journal of the Marine Biological Association of the United Kingdom, 2015
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Indian journal of traditional knowledge
In the present study, endeavor was been made to document the different types of traditional fish ... more In the present study, endeavor was been made to document the different types of traditional fish aggregating devices (FADs) being practiced by the fishermen from the study area and to explore the fishers’ rationale behind their use. Looking into the nature of the study, the information was collected by personal interviews, field observations and conducting focus group discussions with 10-12 practicing fishermen of the meitei community, Manipur state. The study explored a unique traditional fish aggregating wisdom of central valley region of Manipur namely, Phoom namba , Phoomdao thumba (for Air breathing fishes), bunches of weeds (for grass carp) in loktak lake, macrophytes in low lying areas and branches of the tree and twigs (Kao) in the river systems. Further, the study has also revealed that the operation of the fish aggregating techniques ranges from individual to group of fishermen which share the benefits out of the common property resources.
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The Israeli journal of aquaculture = Bamidgeh
In this study we evaluated the effect of three levels of Biogut (a probiotic) on growth performan... more In this study we evaluated the effect of three levels of Biogut (a probiotic) on growth performance of common carp fingerlings. The biogut was incorporated into a formulated diet (protein level: 35%) at 0.5, 1.0 and 1.5% of the diet and designated as T1, T2 and T3 and the fourth group, without biogut, served as control (T0). The diets were fed to common carp fingerlings, stocked at 10 nos. tank-1, with three replicates, for 60 days. Results indicated that the common carp fingerlings fed with the diets containing biogut exhibited higher growth than those fed with the control diet. The survival rate was 100% in all the groups. The average weight and length of common carp was maximal in 0.5% biogut treated group. Specific growth rate, protein efficiency ratio, RNA/DNA ratio and protease activity were also highest in the group fed on biogut at 0.5%. The results clearly exhibit the advantage of the supplementation of biogut at 0.5% in the diet of common carp fingerlings.
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Papers by Soma Das Sarkar