Effect of water quality parameters and climatic influences on reproductive phenology of Macrognathus pancalus in wetland ecosystem: recommending a long-term management approach and conservation policy.

The study conducted an investigation into the reproductive biology of M. pancalus and assessed the influence of water quality parameters and environmental factors on the spawning pattern within the Gajner Beel ecosystem in Bangladesh. A total of 1218 individuals of M. pancalus (46.39% males and 53.61% females) were collected monthly from the Gajner Beel during January to December 2018 using various fishing gears. The total length (TL) of each individual was measured using digital slide calipers, and the whole body weight (BW) was measured using an electronic balance. Fulton's conditions factor (KF) showed significant differences between males and females. The calculated Lm were 11.11 cm, 11.30 cm, and 11.10 cm based on maximum length, gonadosomatic index (GSI), and the logistic model. The spawning season extended from May through August, with June and July being peak months. The average total fecundity was 1495.52 ± 840.24, with a range of 370 to 4069. During peak spawning season, the average temperature and rainfall were 27°C and 370 mm, respectively. Rainfall, dissolved oxygen, total alkalinity, and pH all had a significant (p < 0.01) positive effect whereas temperature and TDS all had a significant (p > 0.01) negative effect on GSI. Annual air temperature in the study area increased by 0.053 °C/year, with a regression coefficient value (r2 = 0.1695), while annual mean rainfall decreased by 5.97mm/year (r2 = 0.076). This research will contribute to the development of conservation and management approaches of Mastacembelidae fish in relation to current climate variability in sub-tropical waters.

Reproductive biology of Lepidocephalichthys guntea: a key conservation approach considering environmental factors in Payra River, Bangladesh.

The guntea loach, Lepidocephalichthys guntea, is categorically common freshwater fish in Southeast Asia. Current study is the first elucidation on the reproductive feature of L. guntea including population structure, sex ratio (SR), size at first maturity (Lm), breeding period, and condition factor, emphasizing on the effect of environmental factors on reproduction of this fish in the Payra River (Southern Bangladesh) during July 2021 to June 2022. Using various conventional gears, 1128 individuals (534 males and 594 females) have been collected. Total length (TL), standard length (SL), and body weight (BW) of each fish were measured. Ovaries were cautiously dissected, removed, and precisely weighed. TL ranges from 4.6 to 9.7 cm (BW = 0.7-9.27 g) for male and 4.6-10.3 cm (BW = 0.8-10.75 g) for female. Both male (47.34%) and female (52.66%) populations were the leading group in 7.00-7.99 cm TL. Overall SR was not notably altered from anticipated value of 1:1 (male:female = 1:1.11). Nonetheless, monthly variations of SR specified females were considerably outnumbered males in each month excluding March-May. Lm range was 6.4-7.0 cm, so larger than Lm is recommended to exploit. Monthly changes in GSI indicated that the main spawning season was from March to June. The spawning season was substantially correlated with rainfall, nonetheless with temperature. Additionally, relative weight indicated that habitat was imbalanced with higher predators. A fishing ban is recommended during peak spawning to protect L. guntea in the Payra River and its surroundings based on current research.

Occurrences, sources, fate and impacts of plastic on aquatic organisms and human health in global perspectives: What Bangladesh can do in future?

Bangladesh is not an exception to the growing global environmental problem of plastic pollution. Plastics have been deemed a blessing for today's world thanks to their inexpensive production costs, low weight, toughness, and flexibility, but poor biodegradability and massive misuse of plastics are to blame for widespread contamination of the environmental components. Plastic as well as microplastic pollution and its adverse consequences have attracted significant investigative attention all over the world. Plastic pollution is a rising concern in Bangladesh, but scientific studies, data, and related information are very scarce in numerous areas of the plastic pollution problem. The current study examined the effects of plastic and microplastic pollution on the environment and human health, and it examined Bangladesh's existing knowledge of plastic pollution in aquatic ecosystems in light of the rapidly expanding international research in this field. We also made an effort to investigate the current shortcomings in Bangladesh's assessment of plastic pollution. This study proposed several management approaches to the persistent plastic pollution problem by analyzing studies from industrialized and emerging countries. Finally, this work pushed investigators to investigate Bangladesh's plastic contamination thoroughly and develop guidelines and policies to address the issue.

Life history traits of Mystus vittatus in the Ganges River, Bangladesh: recommendation for its sustainable management considering climate change.

Freshwater catfishes are regarded primarily as a source of food and sport, so they are highly valuable economically. We comprehensively studied life history features of Mystus vittatus, including sex ratio (SR), population structure, growth pattern, condition, form factor (a3.0), sexual maturity (Lm), spawning season, fecundity, mortality (i.e., total mortality (Z), natural-mortality (MW), and fishing mortality (F)), optimum catchable length (Lopt), length at first capture (Lc), and environmental factors (temperature and rainfall) with management policies from the Ganges River during July 2017 to June 2018. SR (1:1.48) differed noticeably from the expected 1:1 ratio (p < 0.05). Total length (TL) ranged from 6.80-16.00 cm for males and 6.53-18.80 cm for females. The growth was negative allometric for both sexes. Fulton's condition factor was the best one and mean relative weight showed no significant difference from 100 for both sexes that indicates balanced population. Lm was 9.60, 9.70, and 8.80 cm based on the gonadosomatic index (GSI), logistic, and maximum length (Lmax), respectively. Spawning season was April to September and the peak was May to July. Fecundity varied from 5942 to 49,852 (mean ± SD, 11,898 ± 5028) and a positively correlated with TL and BW. Z was 1.80 year-1, Mw was 0.97 year-1, and F was 0.83 year-1. Lopt was 11.14 cm (TL) and Lc was ~ 8.47 cm (TL). Temperature and rainfall both were significantly related with GSI and suitable range of temperature and rainfall for spawning of M. vittatus was 28-34 °C and 200-390 mm, respectively. Long data series pointed that average air temperature was increasing and rainfall was decreasing. By considering all of the above parameters, we can take the proper management actions for M. vittatus and other freshwater catfishes on the Indian sub-continent, to ensure long-term self-sustainability and sustainable harvest for the benefit of fishers and communities.

Effects of COVID-19 pandemic on Baor (Oxbow lake) fisheries: Decreased economic livelihoods and food security.

The COVID-19 pandemic has had a negative impact on the global economy, with Bangladesh as a developing country exhibiting greater vulnerability. This pandemic has negatively affected the livelihoods and food security of the nation. Baor (oxbow lake) fisheries communities also were significantly affected during the pandemic, in terms of incomes, food security, health conditions, etc. Fishers have had to stop harvesting, or lower the quantity, of fishes, the sale of which was the main income source of the baor fishers' community because of reduced consumer demands during the lockdown conditions. The supply chains of fishes and fish culture inputs were also disrupted because of a lack of needed transportation, thereby hindering the availability of this convenient protein source from the fish. All these factors negatively impacted the incomes of the people dependent on this important fishery. If appropriate measures are applied to overcome these various difficulties, the baor fisheries may again contribute significantly to the livelihoods and food security of the population in the southwestern part of Bangladesh.

Assessing stocks of Mystus tengara (Hamilton, 1822) from three different management systems in Baors (Oxbow lake) of southwest Bangladesh: Implications for sustainable management.

This study was conducted to observe the stock assessments of Tengara (Mystus tengara) in three different management systems of Baors (Oxbow lake) such as System-1, System-2, and System-3. In this study, 1806 specimens were sampled using traditional fishing nets to observe growth pattern, population structure, growth parameters, natural mortality (M), fishing mortality (F), total mortality (Z), recruitment pattern, exploitation rate (E), relative yield per-recruit (Y'/R), optimum catchable length, length at first capture, steady state biomass (SSB), and maximum sustainable yield (MSY) from January to December 2021. Digital slide calipers and a digital balance were used to measure each individual's total length (TL) and body weight (BW), respectively. An empirical maximum length-based model was used to calculate size at first sexual maturity (Lm), and optimum catchable length (Lopt) was calculated based on asymptotic length (L∞). The least square linear regression equation was used to determine the regression parameters. The value of regression parameter, 'b' was 3.01 for system-1, 2.78 for system-2, and 2.70 for system-3, indicating that growth pattern of Tengara is isometric in system-1, but negative allometric growth in system-2 and system-3. The highest asymptotic length (L∞) and weight (W∞) of Tengara were found in system-1 (11.19 cm and 13.67 g) in comparison with system-2, (10.98 cm and 12.49 g) and system-3 (9.09 cm and 6.96 g) respectively. The growth coefficient (K) of the von Bertalanffy growth function (VBGF) was 0.72 year-1, 0.72 year-1, and 0.73 year-1 for system-1, system-2 and system-3, respectively. The calculated M, F, Z were 1.72, 1.28, and 3.00 year-1 for system-1, 1.11, 0.67 and 1.78 year-1 for system-2 and 1.12, 0.84 and 1.96 year-1 for system-3 respectively. The calculated life span (tmax) was found 4.19 years for system-1, 4.15 years for system-2 and 4.12 years for system-3. The recruitment patterns showed that the highest relative percentage of recruits were found in July, June and September for system-1, system-2 and system-3 respectively, with the major recruitment peak occurring from April to June for system-1, May to June for system-2 and June to July for system-3. One minor recruitment peak also occurred from August to September in system-1. The exploitation rate was more or less same in all three systems indicating that Tengara is under exploited from all the Baors. The significantly highest SSB and MSY were found in system-1 (22.65 and 12.11 metric tons), compared to system-2 (16.16 and 10.28 metric tons) and system-3 (5.55 and 5.49 metric tons), respectively. Considering the values of regression parameters, recruitment pattern, SSB and MSY, system-1 was found more suitable for Tengara compared to system-2 and system-3 management practices of Baors. Finally, these findings will turn out to be paradigm for the impregnable management of Tengara in Baors of southwest Bangladesh.

Exploring the reproductive features of Clupisoma garua from Ganges River, Bangladesh: insights into eco-climatic factors for sustainable management and advancements in aquaculture practices.

The Garua bacha, Clupisoma garua, holds considerable commercial and nutritional significance as a fish species. This study investigates the relationships between GSI (gonadosomatic index) and eco-climatic conditions, and provides comprehensive insights into several facets of reproduction, such as size at first sexual maturity (Lm), spawning season, peak spawning period, and proposes sustainable management strategies for C. garua in the Ganges River, northwestern, Bangladesh. Since January to December 2017, 570 female individuals have been gathered from the Ganges River using cast nets, gill nets, and square lift nets on a monthly basis. The total length (TL) of the specimens varied from 3.90 to 26.30 cm. Lm was estimated as 14.30 cm based on the results of the TL vs. GSI, MGSI (modified gonadosomatic index), DI (Dobriyal index), 14.00 cm through TL-FL regressions, and 15.18 cm depending on Lmax for this species. Furthermore, the spawning period was observed from May to August, peaking in June and July, based on greater GSI, MGSI, and DI values. Throughout the peak spawning season, there was not a significant differ from a value of 100 in the relative weight (WR) of the female species. During the spawning season, a substantial association between temperature and GSI (p = 0.0038); rainfall and GSI (p = 0.0043); DO and GSI (p = 0.0043); pH and GSI (p = 0.0002); and alkalinity and GSI (p = 0.0001) was detected. Analyzing a 55-year data series (1964-2018), it became clear that an increase in average air temperature of 0.0289 °C and a decrease in rainfall of 2.988 mm per year might possibly delay the spawning season of this species. As a consequence, the results of this study provide crucial information for developing management strategies to safeguard C. garua populations in the Ganges River and its adjacent ecosystems.

Estimating the growth parameters, exploitation rate, biomass and maximum sustainable yield of long whisker catfish Mystus gulio (Hamilton, 1822) in the coastal waters from southwestern Bangladesh.

The research provides a comprehensive analysis of Mystus gulio including growth pattern, growth parameters, recruitment patterns, mortality rates, biomass, exploitation rate (E), and the estimation of maximum sustainable yield (MSY) within the southwestern coastal waters of Bangladesh. From January to December 2017, fishers provided around 1200 specimens. FAO-ICLARM Stock Assessment Tool and Excel-add-in-solver were used to assess stock status through length-frequency data. Indeed, the research findings indicated that the population of M. gulio displayed negative allometric for both individuals (b = 2.53 for male, b = 2.50 for female), as demonstrated by the calculated allometric coefficient value. Nonetheless, the population's dynamic characteristics revealed an asymptotic length (L∞) of 19.34 cm, 23.28 cm and growth coefficient (K) 0.94 year-1 and 0.81 year-1 for male and female M. gulio. The growth performance indexes (Ø') of 2.55 and 2.64 for male and female and maximum lifespan (tmax) 3.20 years and 3.70 years respectively. This study revealed that the slightly variations in the natural mortality rate (M) for both specimens at 1.55 year-1 and 1.59 year-1. The fishing mortality rate (F) 2.75 year-1 and 1.98 year-1and total mortality rate (Z) 4.30 year-1 and 3.57 year-1 for male and females, respectively. The maximum permissible exploitation rate (Emax = 0.421) was lower than the actual exploitation rate (E = 0.63). The MSY was calculated at 67.968 metric tons. Without a doubt, overfishing stands out as the most critical threat to the wild stock. Therefore, it is clear that the existing fishing approach was not efficiently managed the standing stock in a sustainable manner. The findings would be useful for established proper fishing regulations in coastal waters and the surrounding ecosystems.

Evaluating biometric indices for Indian Gagata, Gagata cenia (Hamilton, 1822) through multi-model inferences.

Biometric indices provide crucial information on fish population growth and aquatic habitat well-being. This study offers the first comprehensive elucidation on biometric indices of Gagata cenia (Hamilton, 1822) specifically; population structure, growth pattern and parameters, form factor (a 3.0 ), conditions factors, prey-predator status, reproduction, optimum catchable length (L opt ), mortality and exploitation rate in the Jamuna River, northern Bangladesh. The aim of this study is to estimate stock status of G. cenia in order to protect the declining wild stock. Total of 725 fishes were randomly collected (ranges between 2.7 and 8.5 cm total length (TL), while 0.30-8.24 g body weight (BW)) occasionally using conventional fishing gears during June 2020 to May 2021. The b value of length-weight relationship (TL vs. BW) was 3.33 which indicated positive allometric growth pattern with r 2 value 0.942. Growth parameters were supposed as asymptotic length (L ∞ ) = 9.09 cm, (K) = 0.94 year-1, growth performance index (Ø') = 1.89 and longevity (t max ) = 3.2 year-1 for this population. The calculated a 3.0 was 0.0172 and Fulton's condition (K F ) is the best suited tool for assessing the well-being of this population. Additionally, relative weight (W R ) specifies an imbalanced territory with regard to the occurrence of predators. The size at sexual maturity (L m ) and L opt for combined sexes of G. cenia were 5.4 cm and 6.0 cm, respectively henceforth fish sizes 6.0-6.5 cm TL are recommended for exploitation. The current study verified fishing mortality was significantly lower than natural mortality and the exploitation rate (E) was 0.32 which indicated the stock was under fishing. Our findings would be very beneficial in planning the sustainable and appropriate management of this fish in Bangladesh and nearby ecosystems.

Assessment of Stock Status, Metal Contents with Human Health Risk of Gudusia chapra from Oxbow lake, Bangladesh.

The current study is focused on a comprehensive stock assessment of Gudusia chapra to assess the stock status along with feeding habits, essential minerals content and risk to human health from exposure to heavy metals. A total of 723 specimens from the Bukvora Baor, Bangladesh were used to estimate the total body length (TL) and body weight (W) which ranged from 5.5 to 14.5 cm and 1.62-26.45 g, respectively. The estimated asymptotic length (L ∞) of this species (15.38) was in comparison with average length at 10 cm from 723 specimens along with the rate of 0.70 yr-1 for approaching to asymptotic length. The obtained growth performance index (φ) 2.2 indicates that this species is not economically feasible to bring under aquaculture. At an average annual water surface temperature of 28 °C, natural mortality, 1.71yr-1 indicating good ecological suitability of Bukvora oxbow lake (Baor). The estimated current exploitation ratio (0.24) reflected under-exploitation status with total instantaneous mortality (2.25 years-1) and fishing mortality (0.55 years-1). The recruitment pattern of this species was observed across the year, with main peak occurring during the period of April to May. The estimated total steady state biomass (3.91 metric ton) and MSY (4.40 metric ton) based on length-structured virtual population analysis (VPA) length-structured virtual population analysis (VPA) through FiSAT II schedule indicating the sustainable production of this species. The obtained values of proximate compositions (% of protein, fat, Moisture, ash) showed no significant variations during different seasons throughout the year. The monthly measurements of GaSI showed significant alterations (p < 0.05). The value of essential minerals (Na and Ca) was recorded 9.18 mg and 245.19 mg per 100 g of fish flesh, respectively. Target hazard quotient and Cancer risk for all detected heavy metals were far below the recommended levels by United States Environmental Protection Agency. Therefore, the target fish species from oxbow lake is safe and have no human health risk. Therefore, the outcomes of this research would be very worthwhile in carrying out specific management for G. chapra in Baor ecosystems.

Wildfires in Australia: a bibliometric analysis and a glimpse on 'Black Summer' (2019/2020) disaster.

A wildfire, an unplanned fire that is mainly uncontrolled and originates in combustible vegetation in rural or urban settings, is one of the most pervasive natural catastrophes in some areas, such as Siberia, California and Australia. Many studies, such as standard reviews, have been undertaken to look into the works of literature on wildfires or forest fires and their effects on aquatic and terrestrial ecosystems. Regrettably, conventional literature reviews failed to identify the important researchers, evolving complexities, emerging research hotspots, trends and opportunities for further research on the ground of wildfire study. The present study employs bibliometric analysis to investigate this study area qualitatively and quantitatively. The Scopus database systems and Web of Science Core Collection yielded 78 qualifying papers, which were then evaluated using Biblioshiny (A bibliometrix tool of R-studio). According to the statistics, the discipline is expanding at a pace that is 13.68% faster than average. So far, three key periods of transformation have been documented: preliminary evolution (8 articles; 1999-2005), gentle evolution (14 articles; 2006-2013) and quick evolution (56 articles; 2014 to 2021). Forest Ecology and Management and Science journals have the highest number of publications, accounting for 7.70% of total wildfire-related articles published from 1999 to 2021. However, recent data indicate that investigators are shifting their focus to wildfires, with the term 'Australia' having the highest frequency (91) and 'wildfire' having the second highest (58) as the most appeared keywords. The present study will provide a foundation for future research on wildfire incidence and management by receiving information by synthesising previously published literature in Australia and around the world.

First report on population dynamics and stock status of Badis badis in a wetland ecosystem (NW Bangladesh): Insights from new recorded maximum length.

Badis badis (Hamilton, 1822) is a popular ornamental fish species in the world. This study provides valuable insights into some biological indices of B. badis using a sample of 293 individuals. These individuals were captured from June 2021 to May 2022 using several traditional fish harvesting gears and traps in the Babu Mondoler beel, a wetland ecosystem in NW Bangladesh. Biometric data were collected for each individual, contributing to a comprehensive understanding of this species. The recorded results revealed a wide range of total length (TL), varying from 2.30 to 11.33 cm. Notably, we observed a maximum length of 11.33 cm TL and a maximum body weight (BW) of 18.18 g, ranging from 0.20 to 18.18 g, setting a new record and showcasing the diversity in size within the population. The estimated allometric coefficient (b) showed that combined sexes had negative allometric growth (b = 2.67). Growth parameters were assessed as L∞ = 11.93 cm, K = 0.95 year-1 and Ø' = 2.13. The tmax was 3.16 years. The Lm was measured at 7.02 cm TL and tm = 0.89 year. In this study, KF (1.4240 ± 0.3194) was best for the wellbeing of B. badis in the study area. The a3.0 was estimated at 0.0079 and the relative weight WR (100.90 ± 16.994). Physiological status showed that maximum fatty fish were observed at 10.00-12.00 cm TL; lowest at 4.0-6.00 cm TL. Moreover, the Z, Mw, F and E were estimated to be 3.29 year-1, 1.45 year-1, 1.84 year-1and 0.56, respectively. Additionally, the Lopt for this species was found to be 7.91 cm TL. The findings from this study hold great potential for enhancing the assessment and management of the specimen in the study area and its ecological community. These valuable insights into the population parameters, growth patterns, and exploitation rates of B. badis can inform future management strategies, ensuring the sustainable utilization of this fishery resource in Bangladesh and others neighboring countries.

Species identification, reproductive biology, and nutritional value of marine shellfish (Meretrix lyrata) in the Bay of Bengal.

Meretrix lyrata which is under the family of Veneridae and under the order of Venerida, is a nutritionally and economically important edible mussel in Bangladesh. However, studies on species identification and nutritional value in M. lyrata are scarce. Therefore, a detailed investigation was conducted on (i) species identification of the common edible mussel through DNA-barcoding and morphometrics, (ii) reproductive features, such as size at sexual maturity, spawning, and peak-spawning seasons under different environmental factors, and (iii) nutritional status through proximate analysis of M. lyrata mussel collected from the Bay of Bengal, Bangladesh. The results indicated that the size at sexual maturity for M. lyrata was 4.2 cm and the spawning seasons were significantly affected by the dissolve oxygen and salinity. The study also demonstrated that the spawning of M. lyrata occurred from January to June and December while peak spawning season was May in the Bay of Bengal. The higher protein and moisture contents with lower fat in M. lyrata indicated that are value-added seafood with higher nutritional values for consumers.

Reproductive aspects of Anabas testudineus collected from the Gajner Beel wetland in Bangladesh: implications for its conservation under changing eco-climatic conditions and suggestions for best aquaculture practice.

The freshwater climbing perch, Anabas testudineus, is an economically and nutritionally valuable food fish. This study explores the various reproductive contents (size at sexual maturity, reproductive period and fecundity) of A. testudineus in the Gajner Beel concerning the eco-climatic variabilities and suggests sustainable management policies. A total of 709 individuals were randomly collected from January to December 2019 among 371 females that were sorted out for this study. Total length (TL) ranged from 7.50 to 16.40 cm. Based on the maximum length (Lmax), TL vs. gonadosomatic index (GSI), TL-standard length (SL) regression and logistic model, the size at sexual maturity (Lm) was 10.00 cm, 10.40 cm, 11.00 cm and 11.50 cm, respectively. The spawning season was May to August and peaked in June-July. The Fulton's condition (KF) was suggested as the best condition factor (p < 0.0001), and relative weight (WR) showed no significant difference from 100 for females (p = 0.143). Fecundity was ranged from 9459 to 35,915. A significant relationship was observed between GSI and temperature (p = 0.0016), dissolved oxygen (DO) (p < 0.0001), pH (p < 0.0001), alkalinity (p < 0.001) and climatic parameters (air temperature, p < 0.001 and rainfall, p < 0.001). The data series of 48 years (1971-2019) revealed that the rise of average air temperature by 0.029 °C and the reduction of rainfall by 2.96 mm per year might shift the spawning season of A. testudineus 15-20 later. Therefore, this study will be helpful for the sustainable management and conservation of the wild stocks of A. testudineus in the Gajner Beel and adjoining ecosystems.

Estimation of life history parameters for river catfish Eutropiichthys vacha: insights from multi-models for sustainable management.

The river catfish, Eutropiichthys vacha is a vital protein source for rural communities and has high commercial value, but understanding its life history and management strategies reveals major inadequacies and ambiguities in the riverine ecosystems. Consequently, this study employs multi-models to analyze the life history parameters of E. vacha in the Ganges River (northwestern Bangladesh) from January to December, 2020. The total length (TL) and body weight (BW) of 362 individuals (male = 170, female = 192) were measured by a measuring board and a digital weighing balance, respectively. The overall sex ratio (male: female) was 1.0: 1.13 and did not oscillate statistically from the standard 1:1 ratio (p > 0.05). The TL varied from 6.7-19.2 cm for males and 6.3-19.0 cm for females. The length-frequency distributions (LFDs) revealed females outnumbered in 8.0-9.99 cm TL whereas males in 7.0-7.99 cm TL. The slope (b) of the length-weight relationship (TL vs. BW) for both sexes (b = 2.87) was substantially lower than isometry, specifying negative allometric growth pattern for E. vacha. Sex-specific relative (K R ) and Fulton's (K F ) condition analysis revealed better state of well-being of males than females. Only K F exhibited significant correlation with both BW and TL, hence making it ideal condition for predicting the fitness of E. vacha in this river. Moreover, the relative weight (W R ) suggests an imbalanced habitat for females with higher abundance of predators but suitable for males. The form factor (a 3.0 ) was 0.0062 and 0.0065, whereas the size at first maturity (L m ) and mean natural mortality (M W ) were 11.38 and 11.27 cm TL and 1.29 and 1.28 year-1 for the respective sexes. Besides, the calculated mean optimum catchable length (L opt ) was 13.58 and 13.09 cm TL for each sex. These findings will be crucial for further studies and to recommend appropriate strategy for the sustainable management of E. vacha in the Ganges River and adjacent watersheds.

Reproductive biology of Heteropneustes fossilis in a wetland ecosystem (Gajner Beel, Bangladesh) in relation to eco-climatic factors: Suggesting a sustainable policy for aquaculture, management and conservation.

The stinging catfish, Heteropneustes fossilis (Bloch, 1974) is a commercially important fish species in Asia. This is an important food fish as is enriched with high amounts of protein, iron and calcium. The current research demonstrates the population structure, size at sexual maturity, spawning- and peak-spawning season and fecundity of H. fossilis in an important wetland ecosystem - Gajner Beel in northwestern Bangladesh with an aim of its sustainable conservation through induced breeding and aquaculture practices. A total of 426 stinging catfish captured from the Gajner Beel through monthly sampling from January to December 2019 used in the study. Total length (TL), standard length (SL) and body weight (BW) of individual fishes were measured. The size ranges were with 6.70-24.10 cm TL, 1.37-83.94 g BW. Gonads were removed carefully through ventral dissection and weighted. Lm was 14.02, 13.5, 13.0 and 15.0 cm based on maximum length (Lmax ), TL vs. GSI (%), TL vs. SL and logistic model, respectively. Monthly variations of GSI and maturation stages were confirmed in April to August as spawning season and June as peak spawning month. Fulton's condition factor (KF ) was found to be with significant relations with GSI values. Fecundity was 1,730 to 23,870 and significantly correlated with both TL and BW. Temperature has been increasing 0.029 °C/year with the falling of rainfall at 2.96 mm/year in the study area. Environmental factors -Temperature, rainfall, dissolved oxygen and pH were found to be significantly correlated with GSI. We found the optimal range of temperature (29-31 °C), rainfall (350-380 mm), dissolved oxygen (5.0-6.0 mg/l) and pH (7.1-7.5) for spawning of H. fossilis. The paper recommended the policy guidelines to pave the ways of the aquaculture, conservation and management of H. fossilis in the changing eco-climatic events through specific management measures.

Are there any effects of eco-climatic factors on freshwater prawn reproduction: a study on monsoon river prawn, Macrobrachium malcolmsonii.

Prawns are regarded as delicious food items and a source of income as it is the salient exportable fishery item of Bangladesh and a number of other countries. Climate change may inhibit the general physiological activity of prawns. This study explored the eco-climatic effects on reproduction, including size at first sexual maturity (Lm), spawning season, and fecundity of monsoon river prawn, Macrobrachium malcolmsonii (Milne-Edwards, 1844). The study was carried out in the Ganges (Padma) River basin, northwestern Bangladesh, from January to December 2014. Seven hundred fifty-seven specimens ranging from 0.80 to 18.27 g BW (body weight) with TLs (total length) of 4.20 to 11.52 cm were analyzed. The Lm was estimated as 6.2-6.6 cm. Total fecundity was higher than earlier studies and ranged from 2743 to 122,165 with a mean value of 6715 ± 2437. The spawning season was estimated from April to October with a peak in July. Significant correlation was found between rainfall and the presence of ovigerous females, i.e., spawning season. The number of ovigerous females increased in ≥ 100 mm average rainfall, and the maximum ovigerous female spawned at 250-320 mm rainfall. Spawning season of M. malcolmsonii may have shifted with shifting rainy season as a result of climate change. The findings of our investigation would be useful for sustainable management of the fishery of M. malcolmsonii and other prawn species in the Ganges River, Bangladesh, and adjoining countries with similar eco-climatic factors.

Reproductive performance of Asian stinging catfish Heteropneustes fossilis (Bloch 1794) in the Ganges River (NW Bangladesh) in relation to environmental factors.

Reproduction plays an important role in fish population efficiency and its resiliency to fishing and environment changes. The present study described the comprehensive information on reproductive feature of stinging catfish, Heteropneustes fossilis (Bloch 1794), including size at sexual maturity, spawning season, and fecundity using 622 female individuals sampling by the use of gill net, cast net, and square lift net from January to December 2019 in the Ganges River. We calculated the influences of various environmental parameters which include temperature, dissolved oxygen, pH, and rainfall on the reproductive feature of H. fossilis in the Ganges River. For every specimen, total length (TL), standard length (SL), and body weight (BW) were estimated by measuring board and electronic weighing scale. With ventral dissection of fishes, female gonads were cautiously removed and measured to 0.01 g precision. The gonadosomatic index (GSI), modified gonadosomatic index (MGSI), and Dobriyal index (DI) were used to assess the size at sexual maturity (Lm) and spawning season. According to the results of these indices, Lm was obtained 15.5 cm in TL. Also, TL50 was determined through logistic function as 15.5 cm in TL. Moreover, the highest GSI, MGSI, and DI values indicated the spawning season as of March-August, with peak in May-June. Total fecundity (FT) varied from 2059 to 59,984 with a mean of 25,028 ± 15,048. Temperature and rainfall was statistically correlated with GSI. In addition, long climatic data series analysis denoted that yearly mean atmospheric temperature is rising in 0.028 °C/year and yearly mean rainfall is declining in 2.98 mm/year which may suggest a potential shift of the spawning period of the species in the future if this trend persists. The results of our study might be more useful in imposing particular management and conservation for H. fossilis in the Ganges River and the surroundings.

A review on impacts of COVID-19 on global agricultural system and Scope for Bangladesh after pandemic.

COVID-19 pandemic has had a devastating effect on the global food production system. Large-scale food producing countries restricted exports for food  sovereignty, while small and import-dependent countries are at risk. After COVID-19 pandemic, integrated and planned action is necessary to overcome this global stalemate. In this review paper, we have tried to show the damage caused to global agriculture as well as in Bangladesh due to COVID-19 pandemic. At the same time, the prospects and tasks of Bangladesh in the post-pandemic global economy have also been discussed. Due to the middlemen-based marketing system in Bangladesh, farmers have been deprived of their profits from  the early period. The government should move forward with a long-term planning to find alternative food market such as processing and export alongside the one-way marketing system. On the other hand, it will benefit the farmers' community of Bangladesh, as well as ensure global food security after this pandemic.