Significant decline of water pollution associated with inland fishery across China

Water pollution seriously threatens the sustainable development of fisheries in China.To inform effective pollution control policies,a comprehensive understanding of the fishery environment status is needed.However,nationwide data on the temporal changes of major pollutants in the fishery waters of China are scarce.This study collected data on the major water pollutants,including total nitrogen,total phosphorus,heavy metals,and total petroleum hydrocarbons(TPHs),from 2003 to 2017 to evaluate dynamic changes in the inland fishery water environment across China.We discovered that the levels of four heavy metals(Cu,Zn,Pb,and Cd)and TPH decreased during the 15-year period,corresponding to the reduced national discharge of pollution sources from 2003 to 2015.However,nitrogen and phosphorus levels in the inland fishery waters showed no significant changes during this period.A comparative analysis of water quality in different periods indicated that these improvements were highly associated with effective measures for water pollution control in China.In addition,the decline in pollution was consistent among the three regions of China(north,west,and southeast)from 2003 to 2017,while southeast China exhibited the weakest pollution mitigation among the three regions.These findings suggest that the inland fishery water quality improved during 2003–2017,but still faced eutrophication risk.

Does fishing venture matter for reducing post-harvest loss?Empirical evidence from Bangladesh

The study was conducted to estimate the post-harvest loss(PHL)of inland capture fisheries in Bangladesh based on the fishing venture i.e.,sole proprietorship,partnership and cooperatives using Questionnaire Loss Assessment Method(QLAM).A total of 1339 fishermen were selected using stratified random sampling where 792,485,and 62 were involved in the sole proprietorship,partnership,and cooperatives types of fishing venture respectively.The data were collected from thirty-nine districts across six divisions through the direct interview method covering 92 fish species.The results indicated that Ashar(June-July)to Agrahayon(November-December)was the peak fishing period for every fishing venture.The study revealed that the high volumes of fishes were caught from haor for partnership and cooperatives while river was for sole proprietorship.The study accounted lower PHL for cooperatives than that of sole proprietorship and partnership and found significance differences among them from Tukey’s pairwise test.The estimated PHL was higher for Puti(Puntius chola)in sole proprietorship and partnership whereas Tengra(Gagata cenia)in cooperatives venture.The study suggests to expand the cooperatives fishing ventures widely in Bangladesh where the predominant factors(i.e.,longer harvesting duration,delaying in marketing the fishes and temperature,excess supply,and etc.)of causing PHL in this venture should be taken under consideration.

Fisheries resources of Bangladesh:Present status and future direction

Bangladesh is considered one of the most suitable regions for fisheries in the world,with the world's largest flooded wetland and the third largest aquatic biodiversity in Asia after China and India.This paper reviews the performance of fisheries in Bangladesh using data collected from the Bangladesh Department of Fisheries,and related un-published grey literatures.The findings within describe recent growth within Bangladeshi inland fisheries,primarily in the inland aquaculture sector(2014e2015).This increase in the aquaculture production has been made possible with the implementation of scientific and technological modernization.From 2000 and 2016,aquaculture production increased from 712,640 and 2,060,408 metric t,a much larger quantity than wild capture production(1.023 million t)in 2016.There has also been a recent increase in the value of fishery exports,with more than US$34.08 billion in 2010 rising to more than US$46.60 billion in 2015.However,fisheries production is well below production targets despite the large gains seen in the aquaculture sector.

An optimal management strategy for stochastic population dynamics of released Plecoglossus altivelis in rivers

Excessive predation pressure from the waterfowl Phalacrocorax carbo(Great Cormorant)on Plecoglossus altivelis(Ayu)has recently been a severe problem of river environment in Japan.Local fishery cooperatives are currently suffering from economic difficulties due to decrease of the fish catch of P.altivelis.Local fishery cooperatives and municipalities have been enthusiastically trying to develop countermeasures that can effectively reduce the predation pressure;however,their effectiveness and efficiency have not been systematically quantified well.This aim can be achieved with the help of an appropriate mathematical model.In this paper,based on a pure death process,a practical stochastic control model for population dynamics of released P.altivelis in river environment under predation pressure from P.carbo,harvesting by human,and environmental fluctuations is proposed.Finding an optimal management strategy ultimately reduces to solving a 2D Hamilton–Jacobi–Bellman equation,which is performed with a finite element scheme.Its application to a Japanese river environment successfully computes the optimal management strategy that is consistent with the reality.Numerical sensitivity analysis of the presented mathematical model is also performed for comprehension of dependence of the optimal strategy on the model parameters.

The economic contribution of fish and fish trade in Bangladesh

Bangladesh possesses a large wetland area comprising diversified fisheries resources.Fish and fisheries are an integral part of Bangladesh and have earned its importance due to immense export and revenue potential.The objective of this study was to investigate the trend of fish production,export and import of Bangladesh during the last two decades.Several reviews of the literature were done,numerical data was obtained from the Ministry of Fisheries and Livestock(MoFL),Department of Fisheries(DOF),Bangladesh Bureau of Statistics(BBS).The results showed that fish production has increased in Bangladesh during the last two decades,starting from 17.81 lakh metric tons in 2000–01 and reaching up to 41.34 lakh metric tons in 2016–17.Due to the gradual decline in capture fishery,a significant percentage of total production comes from aquaculture.Hilsha(Tenualosa ilisha)is the largest single-species fishery in Bangladesh which makes the highest contribution to the country's total fish production.Exports of the fish commodity in terms of quantity and value has declined in recent years due to food quality and safety standards.This study has highlighted the contribution of fisheries production in Bangladesh and trade to the country's economy.By paying more attention to the fisheries sector,Bangladesh can boost up its economy.

Fish diversity reduction and assemblage structure homogenization in lakes:A case study on unselective fishing in China

Unselective fishing involves activities that target the entire assemblage rather than specific fish species,size classes,or trophic levels.This common fishing approach has been in practice for decades in inland waters in China but its implications for biodiversity remain unclear.We addressed this issue by studying fish assemblages in freshwater lakes(five fishing lakes,one reference lake,and a total of 51 sampling sites)between pre-and postfishing time-periods in Eastern China during 2017–2019.The effects of lake,fishing period,and their interactions on fish abundance,biomass,and diversity indices were assessed.Multivariate analysis was conducted to test for differences in fish assemblages among lakes and between fishing periods.After the implementation of fishing activities,significant reductions in fish species richness,abundance,biomass,and all three life-history strategies(opportunistic,equilibrium,and periodic)were observed in fishing lakes,whereas opposite trends were observed in the reference lake.Compositional similarity of fish assemblages among fishing lakes increased over the threeyear monitoring period.Our results suggest that unselective fishing reduces fish diversity and homogenizes fish assemblage structure in lakes.These findings have important implications for protecting both biodiversity and fisheries in inland waters in China and are applicable to other countries or regions that rely on fish as a major food source.