The existing study was taken to represent the current information in order to develop a mass-balanced ecosystem model within the resettled maritime boundary area of the Bay of Bengal(BoB),Bangladesh from July 2016 to ...The existing study was taken to represent the current information in order to develop a mass-balanced ecosystem model within the resettled maritime boundary area of the Bay of Bengal(BoB),Bangladesh from July 2016 to June 2017 through ECOPATH approach covering over 90 000 km2.A total of 19 functional groups were considered representing all trophic levels in the foodweb where estimated trophic interactions between the groups were varied from 1(primary producers and detritus)to 3.45(sharks).The ecotrophic efficiency(EE)of most of the consumers was greater than 0.80;symbolizing a largely exploited ecosystem and high energy transfer from lower to higher trophic levels.Moreover,the gross efficiency(0.001 8)and transfer efficiency(11.12%)of the whole system symbolizes the“Developing Systems”with somewhat maturity currently.Ecosystem’s overhead(64.6)and ascendancy(35.4)also designate the ecosystem’s stability.Thus,this study determines that the resettled maritime area of BoB reserves significant backup strength to face stress situations having capacity to rapid restoration to the original states.展开更多
The Atlantic tripletail(Lobotes surinamensis)is a high revenue-generating fish species predominantly caught by mechanized artisanal fishers community and the most available member of its family in Bangladesh.This is a...The Atlantic tripletail(Lobotes surinamensis)is a high revenue-generating fish species predominantly caught by mechanized artisanal fishers community and the most available member of its family in Bangladesh.This is a ground work of fish stock assessment study in the Bay of Bengal region to explore the life history parameters and associated biomass of this species,using three length-based approaches of TropFishR,the length-based Bayesian biomass estimation(LBB),and Froese’s length based indicators(LBIs).An almost homogenous body growth pattern(b=3.07;R^(2)=0.98)was observed in the length-weight relationship of tripletail.The life history parameters for tripletail,as determined by the von Bertalanffy Growth Function(VBGF)model,were L_(∞)=113.36 cm and k=0.51/a.The length converted catch curve(LCCC)yielded an estimation of the total mortality(Z=1.77/a),with the natural mortality estimated at(M=0.53/a)and the fishing mortality estimated at(F=1.24/a).But,the ratio of mortality(F/M=0.15)by LBB captured the non-fully exploited status of biomass(B/B_(MSY)=2.1).LBI analysis indicated that the tripletail fishery’s spawning stock biomass is greater than the target and limit reference points,indicating a healthy state of biomass.展开更多
This research aims to identify the morphological changes of the Padma River due to the effects of anthropogenic climate change. The morphological changes were measured by aerial satellite images and their historical c...This research aims to identify the morphological changes of the Padma River due to the effects of anthropogenic climate change. The morphological changes were measured by aerial satellite images and their historical comparison, terrestrial survey, sedimentation in the riverbed, water flow, water discharge, siltation, and erosion along the river, etc. The Padma River has been analyzed over the period from 1971 to 2020 using multi-temporal Landsat images and long-term water flow data. The climatic parameters data related to temperature and rainfall were collected from 21 metrological stations distributed throughout Bangladesh over a 50-year period (1965-2015) to evaluate the magnitude of these changes statistically and spatially. The Padma, traditionally considered as a dominantly meandering river, is switching over into a braided river due to its highly susceptible nature of erosion and deposition. Results reveal that the tidal range is high during the dry season and increases from upstream to downstream of the river. Climate change may bring changes upstream by changing rainfall intensity, flood severity, and extreme temperature. More inundation can occur due to sedimentation, and more bank erosion can occur at the same time. An exponential increase of morphological activity with increased river flow, water discharge, bank erosion might substantially increase in the future. The changes in the flow introduced by climate change would impact the morphology of the Padma River of Bangladesh during the monsoon. A major change has been observed in the location of the bank and channel, as well as bars, along with their geometry and morphology over time. It is also observed that the bank line is not stable and migrated continuously. The overall width of the Padma River is varied significantly during the last 50 years. Maps and Landsat images represented that the river channel is shifting abnormally. Both climatic parameters and anthropogenic activity play an important role in fish biology and production. From this study, it is hypothesized that this assessment’s findings might help understand the overall hydrodynamic and morphological nature of the Padma River. It will suggest possible future developmental works that might be implemented on this river.展开更多
The Sundarban Mangrove Forest(SMF)is an intricate ecosystem containing the most varied and profuse natural resources of Bangladesh.This study presents empirical research,based on primary and secondary data,regarding t...The Sundarban Mangrove Forest(SMF)is an intricate ecosystem containing the most varied and profuse natural resources of Bangladesh.This study presents empirical research,based on primary and secondary data,regarding the social-ecological system(SES),social-ecological dynamics,different stakeholders and relevant management policies of small-scale or artisanal fisheries such as the SMF;showing how,despite extensive diversification,the livelihood activities of the artisanal fishers in the SMF all depend on the forest itself.Regardless of this critical importance of mangroves,however,deforestation continues due to immature death of mangroves,illegal logging,increased salinity,natural disasters and significant household consumption of mangrove wood by local people.As the mangroves are destroyed fish stocks,and other fishery resources are reduced,leading to moves of desperation among those whose livelihood has traditionally been fishing.The present study also considers several risks and shock factors in the fishers'livelihood:attacks by wild animals(especially tigers)and local bandits,illness,natural disasters,river bank erosion,and the cost of paying off corrupt officials.The artisanal fishers of the SMF have adopted different strategies for coping with these problems:developing partnerships,violating the fisheries management laws and regulations,migrating,placing greater responsibility on women,and bartering fishing knowledge and information.This study shows how the social component(human),the ecological component(mangrove resources)and the interphase aspects(local ecological knowledge,stakeholder's interest,and money lenders or middle man roles)of the SMF as an SES are linked in mutual interaction.It furthermore considers how the social-ecological dynamics of the SMF have negative impacts on artisanal fishermen's livelihoods.Hence there is an urgency to update existing policies and management issues for the sustainable utilization of the SMF resources,eventually contributing to the improvement of the artisanal fishers'livelihoods.展开更多
Shrimps are recognized as the white gold of Bangladesh because it is the second largest export earning product after garments sector.The brown shrimp(M.monoceros)have high growth rates together with that they tol...Shrimps are recognized as the white gold of Bangladesh because it is the second largest export earning product after garments sector.The brown shrimp(M.monoceros)have high growth rates together with that they tolerate wide ranges of salinity and environmental parameters which makes them highly attractive for culture purposes.The purposes of this research were to assess the cultural performance and economic profitability of brown shrimp(Metapenaeus monoceros)in brackish water ponds.This research lasted from February to June 2020 under three different stocking densities such as 35,45 and 55 individuals/m2 in treatments T1,T2 and T3 at Bangladesh Fisheries Research Institute,Brackishwater Station,Paikgacha,Khulna.After 90 days culture periods the total production was 1703.32±144.48,2768.25±167.63 and 2535.03±253.52 kg/ha in T1,T2 and T3 respectively which was significantly higher(p<0.05)in T2 compared to T1 and T2.Benefit cost ratio(BCR)was 0.32,0.87 and 0.52 in T1,T2 and T3 respectively and found significantly higher(p<0.05)in T2 than T1 and T3.Both cultural performance and economic analysis imply that brown shrimp(M.monoceros)with a stocking density of 450000 individuals/ha might be environment conciliatory and economically enduring in coastal areas of Bangladesh.展开更多
The anadromous Hilsa shad(Tenualosa ilisha)fishery is the prime single species fishery of Bangladesh that driven by open access system which was selected for this study.Key purpose of this study was to assess the MSY(...The anadromous Hilsa shad(Tenualosa ilisha)fishery is the prime single species fishery of Bangladesh that driven by open access system which was selected for this study.Key purpose of this study was to assess the MSY(Maximum Sustainable Yield)in order to review the effectivity of the ongoing management policy of this fishery.For this reason,time series maritime or downstream catch-effort data of the Bay of Bengal were assembled from the Department of Fisheries,Bangladesh.MSY,CPUE and other population parameters were estimated through Surplus Production Models(SPMs)using computer software packages of CEDA,ASPIC and TropFishR.Assessed biological reference points of MSY from the best fitted CEDA package was 282,100 t(R^(2)=0.822)for the normal assumptions of the Schaefer and Pella-Tomlinson models.MSY values from the ASPIC packages(324,100 t and 263,500 t;for Fox and Schaefer model)and Schaefer model from TropFishR(345,486t)were larger than the catch in 2017(278,948 t).The values of F ratio(F/FMSY)for all SPMs were found less than 1 and B ratio(B/BMSY)were greater than 1 that clearly indicate the gradual upsurge of the Hilsa stock.Based on the above findings of BRPs,it also proves the effectivity of the current“Hilsa fishery management action plan”by the authorities.展开更多
Tilapiine breeding success is season-dependent,with very rare exceptions.The female(f)to male(m)ratio differences showed significant variations in fruitful breeding.Furthermore,the female-to-male ratio in any hybridiz...Tilapiine breeding success is season-dependent,with very rare exceptions.The female(f)to male(m)ratio differences showed significant variations in fruitful breeding.Furthermore,the female-to-male ratio in any hybridization protocol involving reciprocal crosses may be the most influential factor in determining breeding seasonality.The innate genetic traits of tilapia,a prominent contributor to global aquaculture production,enable them to easily adapt to a wide range of aquatic environments,rendering them suitable for domestication.The study aimed to determine the breeding timeframe of Nile tilapia(Oreochromis niloticus,N)through interspecific monogamous/two-parent reciprocal crossing with Mozambique tilapia(O.mossambicus,M).Considering preselected genotypic characteristics by PrlLK microsatellite marker,different combinations of hybrid reciprocal crosses were performed in breeding hapa(3×3×3 cubic feet)inside an indoor plastered cemented tank and then in an outdoor earthen pond facility.Total 11 parental pairs were attempted to propagate inside a cemented tank with(9 pairs)and without(2 pairs)hapa during early April to mid-June.Unfortunately,the trials failed to produce any successful breeding within the schedule.Among those 11 pairs,6 pairs were Nf×Mm and 5 pairs were Mf×Nm cross.In the earthen pond inside hapa,a total of 18 pairs were attempted where seven breeding successes were reported without demonstrating any dependency for hybridizations over cross types or genotypes and for individuals over sex or species.Successful breeding were reported from the month of May to November.There were few overlapping months of successful breeding for different grouping categories.During the successful breeding period,there were no successful outcomes in both August and October.An inadvertent all-female F1 generation was observed for Mf×Nm crosses,while the reciprocal cross Nf×Mm produced an F1 generation with a nearly 1:1 female to male ratio.The F1 sex ratios exhibited a significant reliance on parental genotypic combinations(p=5.4e-11).The success stories from different cross combinations would help to frame the breeding protocol for future research.More precisely,for arranging a breeding schedule in freshwater earthen ponds inside hapa for a monogamous/two-parent hybrid cross the study light a close insight.展开更多
Objective:To optimize the dose of 3 commonly used growth promoters,viz.,Nuricell-Aqua(composition:glucomannan complex and mannose polymer),Hepaprotect-Aqua(composition:β-glucan,mannose polymer and essential oil)and R...Objective:To optimize the dose of 3 commonly used growth promoters,viz.,Nuricell-Aqua(composition:glucomannan complex and mannose polymer),Hepaprotect-Aqua(composition:β-glucan,mannose polymer and essential oil)and Rapid-Grow(composition:organic acid and their salt,β-glucan,mannose oligosaccharide and essential oil),using Thai pangas(Pangasiandon hypophthalmus)as cultured species.Methods:Thai pangas fingerlings with an average length and weight of 11 cm and 10 g were reared under laboratory condition and growth promoters were fed after incorporating them with a test diet at a ratio of 10%of their body weight for a period of 28 d.Estimation of data on growth such as weight gain(g),specific growth rate,survivability(%)test in each aquarium were conducted and data were analyzed using statistical software.Results:After 28 d of feeding with Nutricell-Aqua,10 mg/(20 g feed·day),which was the dose recommended by the manufacturer,was found better.When Hepaprotect-Aqua and Rapid-Grow were employed,performance was found to be better with the dose of 60 mg/(20 g feed·day)which was 1.5 times higher than the dose recommended by the corresponding manufacturer.Conclusions:These results suggest that chemicals and feed additives marketed in Bangladesh Fish Feed Market need further testing under Bangladesh climatic condition before being marketed.展开更多
Crassostrea(Magallana)saidii has been commercially ranched in Malaysia and consumed for more than 160 years,but it was only recently identified as a new species to science.This study was conducted to evaluate the repr...Crassostrea(Magallana)saidii has been commercially ranched in Malaysia and consumed for more than 160 years,but it was only recently identified as a new species to science.This study was conducted to evaluate the reproductive phenology of C.(M.)saidii.Samples of 30 individual oysters were taken monthly for 15 months from the sole population at Sungai Muar estuary in Johor,Malaysia.The sex ratio was 1:1.64(male:female)for all examined specimens,with female numbers significantly higher.Hermaphrodism was detected in 1.56%of all samples.Spawning peaks in April(2019)and November(2018 and 2019),and were positively associated with the increased rainfall upstream.Gametogenesis occurred throughout the research period with temporal variations.The highest values of maturity index(MI)were recorded in March,August and October 2019,when most oysters were in matured and maturing stages.Condition index(CI)ranged from 31.90±1.25(April 2019)to 70.03±3.23(October 2019),exhibiting two peaks(March and October 2019)and subsequently reduced in CI indicating spawning consistency with histological observations.Anthropogenic stressors such as heavy sedimentation and inland development are threatening the survival of this species.The understanding of their reproductive biology is essential to ensure the survival and sustainability of C.(M.)saidii fishery.展开更多
基金The Fundamental Research Funds for the Central Universities of China under contract No.201562030
文摘The existing study was taken to represent the current information in order to develop a mass-balanced ecosystem model within the resettled maritime boundary area of the Bay of Bengal(BoB),Bangladesh from July 2016 to June 2017 through ECOPATH approach covering over 90 000 km2.A total of 19 functional groups were considered representing all trophic levels in the foodweb where estimated trophic interactions between the groups were varied from 1(primary producers and detritus)to 3.45(sharks).The ecotrophic efficiency(EE)of most of the consumers was greater than 0.80;symbolizing a largely exploited ecosystem and high energy transfer from lower to higher trophic levels.Moreover,the gross efficiency(0.001 8)and transfer efficiency(11.12%)of the whole system symbolizes the“Developing Systems”with somewhat maturity currently.Ecosystem’s overhead(64.6)and ascendancy(35.4)also designate the ecosystem’s stability.Thus,this study determines that the resettled maritime area of BoB reserves significant backup strength to face stress situations having capacity to rapid restoration to the original states.
基金Supported by the special research fund of Ocean University of China(No.201562030)。
文摘The Atlantic tripletail(Lobotes surinamensis)is a high revenue-generating fish species predominantly caught by mechanized artisanal fishers community and the most available member of its family in Bangladesh.This is a ground work of fish stock assessment study in the Bay of Bengal region to explore the life history parameters and associated biomass of this species,using three length-based approaches of TropFishR,the length-based Bayesian biomass estimation(LBB),and Froese’s length based indicators(LBIs).An almost homogenous body growth pattern(b=3.07;R^(2)=0.98)was observed in the length-weight relationship of tripletail.The life history parameters for tripletail,as determined by the von Bertalanffy Growth Function(VBGF)model,were L_(∞)=113.36 cm and k=0.51/a.The length converted catch curve(LCCC)yielded an estimation of the total mortality(Z=1.77/a),with the natural mortality estimated at(M=0.53/a)and the fishing mortality estimated at(F=1.24/a).But,the ratio of mortality(F/M=0.15)by LBB captured the non-fully exploited status of biomass(B/B_(MSY)=2.1).LBI analysis indicated that the tripletail fishery’s spawning stock biomass is greater than the target and limit reference points,indicating a healthy state of biomass.
文摘This research aims to identify the morphological changes of the Padma River due to the effects of anthropogenic climate change. The morphological changes were measured by aerial satellite images and their historical comparison, terrestrial survey, sedimentation in the riverbed, water flow, water discharge, siltation, and erosion along the river, etc. The Padma River has been analyzed over the period from 1971 to 2020 using multi-temporal Landsat images and long-term water flow data. The climatic parameters data related to temperature and rainfall were collected from 21 metrological stations distributed throughout Bangladesh over a 50-year period (1965-2015) to evaluate the magnitude of these changes statistically and spatially. The Padma, traditionally considered as a dominantly meandering river, is switching over into a braided river due to its highly susceptible nature of erosion and deposition. Results reveal that the tidal range is high during the dry season and increases from upstream to downstream of the river. Climate change may bring changes upstream by changing rainfall intensity, flood severity, and extreme temperature. More inundation can occur due to sedimentation, and more bank erosion can occur at the same time. An exponential increase of morphological activity with increased river flow, water discharge, bank erosion might substantially increase in the future. The changes in the flow introduced by climate change would impact the morphology of the Padma River of Bangladesh during the monsoon. A major change has been observed in the location of the bank and channel, as well as bars, along with their geometry and morphology over time. It is also observed that the bank line is not stable and migrated continuously. The overall width of the Padma River is varied significantly during the last 50 years. Maps and Landsat images represented that the river channel is shifting abnormally. Both climatic parameters and anthropogenic activity play an important role in fish biology and production. From this study, it is hypothesized that this assessment’s findings might help understand the overall hydrodynamic and morphological nature of the Padma River. It will suggest possible future developmental works that might be implemented on this river.
基金We thank the fishers and other stakeholders who generously shared their time and knowledge.We are grateful to DAAD(Deutscher Akademisher Austausdienst),for financial support to conduct the research.We thank the anonymous reviewers and the editorial board for their helpful comments and suggestions on earlier versions of the manuscript.Special thanks to David Huisjen for helping with the English edition.
文摘The Sundarban Mangrove Forest(SMF)is an intricate ecosystem containing the most varied and profuse natural resources of Bangladesh.This study presents empirical research,based on primary and secondary data,regarding the social-ecological system(SES),social-ecological dynamics,different stakeholders and relevant management policies of small-scale or artisanal fisheries such as the SMF;showing how,despite extensive diversification,the livelihood activities of the artisanal fishers in the SMF all depend on the forest itself.Regardless of this critical importance of mangroves,however,deforestation continues due to immature death of mangroves,illegal logging,increased salinity,natural disasters and significant household consumption of mangrove wood by local people.As the mangroves are destroyed fish stocks,and other fishery resources are reduced,leading to moves of desperation among those whose livelihood has traditionally been fishing.The present study also considers several risks and shock factors in the fishers'livelihood:attacks by wild animals(especially tigers)and local bandits,illness,natural disasters,river bank erosion,and the cost of paying off corrupt officials.The artisanal fishers of the SMF have adopted different strategies for coping with these problems:developing partnerships,violating the fisheries management laws and regulations,migrating,placing greater responsibility on women,and bartering fishing knowledge and information.This study shows how the social component(human),the ecological component(mangrove resources)and the interphase aspects(local ecological knowledge,stakeholder's interest,and money lenders or middle man roles)of the SMF as an SES are linked in mutual interaction.It furthermore considers how the social-ecological dynamics of the SMF have negative impacts on artisanal fishermen's livelihoods.Hence there is an urgency to update existing policies and management issues for the sustainable utilization of the SMF resources,eventually contributing to the improvement of the artisanal fishers'livelihoods.
文摘Shrimps are recognized as the white gold of Bangladesh because it is the second largest export earning product after garments sector.The brown shrimp(M.monoceros)have high growth rates together with that they tolerate wide ranges of salinity and environmental parameters which makes them highly attractive for culture purposes.The purposes of this research were to assess the cultural performance and economic profitability of brown shrimp(Metapenaeus monoceros)in brackish water ponds.This research lasted from February to June 2020 under three different stocking densities such as 35,45 and 55 individuals/m2 in treatments T1,T2 and T3 at Bangladesh Fisheries Research Institute,Brackishwater Station,Paikgacha,Khulna.After 90 days culture periods the total production was 1703.32±144.48,2768.25±167.63 and 2535.03±253.52 kg/ha in T1,T2 and T3 respectively which was significantly higher(p<0.05)in T2 compared to T1 and T2.Benefit cost ratio(BCR)was 0.32,0.87 and 0.52 in T1,T2 and T3 respectively and found significantly higher(p<0.05)in T2 than T1 and T3.Both cultural performance and economic analysis imply that brown shrimp(M.monoceros)with a stocking density of 450000 individuals/ha might be environment conciliatory and economically enduring in coastal areas of Bangladesh.
基金This work is supported by the special research fund of Ocean University of China(201022001).
文摘The anadromous Hilsa shad(Tenualosa ilisha)fishery is the prime single species fishery of Bangladesh that driven by open access system which was selected for this study.Key purpose of this study was to assess the MSY(Maximum Sustainable Yield)in order to review the effectivity of the ongoing management policy of this fishery.For this reason,time series maritime or downstream catch-effort data of the Bay of Bengal were assembled from the Department of Fisheries,Bangladesh.MSY,CPUE and other population parameters were estimated through Surplus Production Models(SPMs)using computer software packages of CEDA,ASPIC and TropFishR.Assessed biological reference points of MSY from the best fitted CEDA package was 282,100 t(R^(2)=0.822)for the normal assumptions of the Schaefer and Pella-Tomlinson models.MSY values from the ASPIC packages(324,100 t and 263,500 t;for Fox and Schaefer model)and Schaefer model from TropFishR(345,486t)were larger than the catch in 2017(278,948 t).The values of F ratio(F/FMSY)for all SPMs were found less than 1 and B ratio(B/BMSY)were greater than 1 that clearly indicate the gradual upsurge of the Hilsa stock.Based on the above findings of BRPs,it also proves the effectivity of the current“Hilsa fishery management action plan”by the authorities.
基金supported by a grant of BAS-USDA Program Project(BAS-USDA-PALS-BAU–FI–43),Bangladesh to M Sadiqul Islam.
文摘Tilapiine breeding success is season-dependent,with very rare exceptions.The female(f)to male(m)ratio differences showed significant variations in fruitful breeding.Furthermore,the female-to-male ratio in any hybridization protocol involving reciprocal crosses may be the most influential factor in determining breeding seasonality.The innate genetic traits of tilapia,a prominent contributor to global aquaculture production,enable them to easily adapt to a wide range of aquatic environments,rendering them suitable for domestication.The study aimed to determine the breeding timeframe of Nile tilapia(Oreochromis niloticus,N)through interspecific monogamous/two-parent reciprocal crossing with Mozambique tilapia(O.mossambicus,M).Considering preselected genotypic characteristics by PrlLK microsatellite marker,different combinations of hybrid reciprocal crosses were performed in breeding hapa(3×3×3 cubic feet)inside an indoor plastered cemented tank and then in an outdoor earthen pond facility.Total 11 parental pairs were attempted to propagate inside a cemented tank with(9 pairs)and without(2 pairs)hapa during early April to mid-June.Unfortunately,the trials failed to produce any successful breeding within the schedule.Among those 11 pairs,6 pairs were Nf×Mm and 5 pairs were Mf×Nm cross.In the earthen pond inside hapa,a total of 18 pairs were attempted where seven breeding successes were reported without demonstrating any dependency for hybridizations over cross types or genotypes and for individuals over sex or species.Successful breeding were reported from the month of May to November.There were few overlapping months of successful breeding for different grouping categories.During the successful breeding period,there were no successful outcomes in both August and October.An inadvertent all-female F1 generation was observed for Mf×Nm crosses,while the reciprocal cross Nf×Mm produced an F1 generation with a nearly 1:1 female to male ratio.The F1 sex ratios exhibited a significant reliance on parental genotypic combinations(p=5.4e-11).The success stories from different cross combinations would help to frame the breeding protocol for future research.More precisely,for arranging a breeding schedule in freshwater earthen ponds inside hapa for a monogamous/two-parent hybrid cross the study light a close insight.
基金Supported by Bangladesh Fisheries Research Institute with Grant No:BFRI/ARP/10/3161(4).
文摘Objective:To optimize the dose of 3 commonly used growth promoters,viz.,Nuricell-Aqua(composition:glucomannan complex and mannose polymer),Hepaprotect-Aqua(composition:β-glucan,mannose polymer and essential oil)and Rapid-Grow(composition:organic acid and their salt,β-glucan,mannose oligosaccharide and essential oil),using Thai pangas(Pangasiandon hypophthalmus)as cultured species.Methods:Thai pangas fingerlings with an average length and weight of 11 cm and 10 g were reared under laboratory condition and growth promoters were fed after incorporating them with a test diet at a ratio of 10%of their body weight for a period of 28 d.Estimation of data on growth such as weight gain(g),specific growth rate,survivability(%)test in each aquarium were conducted and data were analyzed using statistical software.Results:After 28 d of feeding with Nutricell-Aqua,10 mg/(20 g feed·day),which was the dose recommended by the manufacturer,was found better.When Hepaprotect-Aqua and Rapid-Grow were employed,performance was found to be better with the dose of 60 mg/(20 g feed·day)which was 1.5 times higher than the dose recommended by the corresponding manufacturer.Conclusions:These results suggest that chemicals and feed additives marketed in Bangladesh Fish Feed Market need further testing under Bangladesh climatic condition before being marketed.
文摘Crassostrea(Magallana)saidii has been commercially ranched in Malaysia and consumed for more than 160 years,but it was only recently identified as a new species to science.This study was conducted to evaluate the reproductive phenology of C.(M.)saidii.Samples of 30 individual oysters were taken monthly for 15 months from the sole population at Sungai Muar estuary in Johor,Malaysia.The sex ratio was 1:1.64(male:female)for all examined specimens,with female numbers significantly higher.Hermaphrodism was detected in 1.56%of all samples.Spawning peaks in April(2019)and November(2018 and 2019),and were positively associated with the increased rainfall upstream.Gametogenesis occurred throughout the research period with temporal variations.The highest values of maturity index(MI)were recorded in March,August and October 2019,when most oysters were in matured and maturing stages.Condition index(CI)ranged from 31.90±1.25(April 2019)to 70.03±3.23(October 2019),exhibiting two peaks(March and October 2019)and subsequently reduced in CI indicating spawning consistency with histological observations.Anthropogenic stressors such as heavy sedimentation and inland development are threatening the survival of this species.The understanding of their reproductive biology is essential to ensure the survival and sustainability of C.(M.)saidii fishery.
