In the Indian Ocean, bigeye tuna supports one of the most important fisheries in the world. This fishery mainly consists of two components: longline and purse seine fisheries. Evidence of overfishing and stock depleti...In the Indian Ocean, bigeye tuna supports one of the most important fisheries in the world. This fishery mainly consists of two components: longline and purse seine fisheries. Evidence of overfishing and stock depletion of bigeye tuna calls for an evaluation of alternative management strategies. Using an age-structured operating model, parameterize dwith the results derived in a recent stock assessment,we evaluated the effectiveness of applying constant fishing mortality (CF) and quasi-constant fishing mortality (QCF) strategies to reduce fishing effort of purse seining with fish aggregating devices (FADs) at different rates. Three different levels of productivity accounted for the uncertainty in our understanding of stock productivity. The study shows that the results of CF and QCF are similar. Average SSB and catchduring simulation years would be higher if fishing mortality of FAD-associated purse seiningwas reduced rapidly. The banning or rapid reduction of purse seining with FAD resulted in a mean catch, and catch in the last simulation year, higher than that of the base case in which no change was made to the purse seine fishery. This could be caused by growth overfishing by purse seine fisheries with FADs according to the per-recruit analysis. These differences would be more obvious when stock productivity was low. Transferring efforts of FAD-associated purse seining to longline fisheries is also not feasible.Our study suggests that changes are necessary to improve the performance of the current management strategy.展开更多
In the frame of the present study, we examined the wheat sector with respect to economic and social sustainability. Accordingly, two research questions were formulated： （1） Is wheat production sustainable in econom...In the frame of the present study, we examined the wheat sector with respect to economic and social sustainability. Accordingly, two research questions were formulated： （1） Is wheat production sustainable in economic terms？ and （2） Is wheat production sustainable in social terms？ Our view is that the content of sustainability can be defined on a case-by-case basis, and in our case, wheat production provides this content. To answer the research questions, we collected statistical data on the production area, average yield, production volume, selling price, consumption of wheat, and evaluated the tendencies prevalent in the sector. We suppose that in social terms, sustainability means maintaining consumption at least at a constant level, knowing that this sector produces considerable share of the direct and indirect food raw materials. A chief dilemma is that world population is continuously growing, although the size of the cultivated area in the wheat sector has not indicated significant changes over the past few decades. Unless increasing the yields, severe decrease may occur in the per capita production of wheat in the long run. In this case, the current consumption level will not be sustainable in the medium run. In addition, in the long run, it may even have influence on the consumption level of other commodities.展开更多
基金Supported by the Shanghai Ocean University Graduate School (PhD Dissertation Grant)the Project of Shanghai Science and Technology Innovation(No.12231203900)+4 种基金the National Natural Science Foundation of China(No.NSFC41276156)the Industrialization Program of the National Development and Reform Commission(No.2159999)the Shanghai Leading Academic Discipline Projectthe National Distant-water Fisheries Engineering Research Center,the Scientific Observing and Experimental Station of Oceanic Fishery Resources,Ministry of Agriculture,China.Y.supported by the Shanghai Leading Teacher Program
文摘In the Indian Ocean, bigeye tuna supports one of the most important fisheries in the world. This fishery mainly consists of two components: longline and purse seine fisheries. Evidence of overfishing and stock depletion of bigeye tuna calls for an evaluation of alternative management strategies. Using an age-structured operating model, parameterize dwith the results derived in a recent stock assessment,we evaluated the effectiveness of applying constant fishing mortality (CF) and quasi-constant fishing mortality (QCF) strategies to reduce fishing effort of purse seining with fish aggregating devices (FADs) at different rates. Three different levels of productivity accounted for the uncertainty in our understanding of stock productivity. The study shows that the results of CF and QCF are similar. Average SSB and catchduring simulation years would be higher if fishing mortality of FAD-associated purse seiningwas reduced rapidly. The banning or rapid reduction of purse seining with FAD resulted in a mean catch, and catch in the last simulation year, higher than that of the base case in which no change was made to the purse seine fishery. This could be caused by growth overfishing by purse seine fisheries with FADs according to the per-recruit analysis. These differences would be more obvious when stock productivity was low. Transferring efforts of FAD-associated purse seining to longline fisheries is also not feasible.Our study suggests that changes are necessary to improve the performance of the current management strategy.
文摘In the frame of the present study, we examined the wheat sector with respect to economic and social sustainability. Accordingly, two research questions were formulated： （1） Is wheat production sustainable in economic terms？ and （2） Is wheat production sustainable in social terms？ Our view is that the content of sustainability can be defined on a case-by-case basis, and in our case, wheat production provides this content. To answer the research questions, we collected statistical data on the production area, average yield, production volume, selling price, consumption of wheat, and evaluated the tendencies prevalent in the sector. We suppose that in social terms, sustainability means maintaining consumption at least at a constant level, knowing that this sector produces considerable share of the direct and indirect food raw materials. A chief dilemma is that world population is continuously growing, although the size of the cultivated area in the wheat sector has not indicated significant changes over the past few decades. Unless increasing the yields, severe decrease may occur in the per capita production of wheat in the long run. In this case, the current consumption level will not be sustainable in the medium run. In addition, in the long run, it may even have influence on the consumption level of other commodities.
