In mixed fisheries where there is an increased ecological interdependence between two or more target species, the possibilities of fishing these species must be determined jointly, since catches of one species will im...In mixed fisheries where there is an increased ecological interdependence between two or more target species, the possibilities of fishing these species must be determined jointly, since catches of one species will impact the natural growth not only of that species but of the others, as well. The objective of this paper is to develop a predator-prey model for two major species caught by the EU fishing fleet on European Union fishing grounds. The predator and prey’s population dynamics follow the Lotka-Volterra equation and are assumed to be logic-based, and a lineal interaction between the predator and prey populations is assumed. Optimal single owner multispecies fishery management is analysed, and the applied model is solved, obtaining the equilibrium value of biomasses, catches, and net benefits of the mixed fishery. The results show that the MSY of the predator is higher than that estimated by ICES, while MSY for prey is lower. The sensitivity analysis of the results reveals that the biomass levels of both species decrease as the discount rate increases, while catches increase.展开更多
This paper examines the need for a return to a systemic,holistic,and normative approach to designing human settlements that has been neglected with the decline of the Welfare State and the shift to iecemeal,freewheeli...This paper examines the need for a return to a systemic,holistic,and normative approach to designing human settlements that has been neglected with the decline of the Welfare State and the shift to iecemeal,freewheeling,marked-based development during the unprecedented explosion of construction in the last thirty years.The need for a change is brought about by the current ecological and economic crises linked to a high degree to the current belief that the quality of cities emerges from the added-value of individual buildings or through the assemblage of individual structures put together like a building.This paper argues that a city is not like a building.The contemporary city is characterized by an unprecedented number of problems.These problems cannot be handled by individual good will or simple preventive or corrective actions by architects and developers as it has been done the last three decades.What is needed is an overall systemic framework of planning that ① is driven by normative criteria,② can handle a high degree of complexity and interdependence of factors,and ③ can deal with unanticipated,unintended,long-term irreversible environmental impacts that characterize the "third ecology," the inseparable complex of the natural and the human-made.展开更多
文摘In mixed fisheries where there is an increased ecological interdependence between two or more target species, the possibilities of fishing these species must be determined jointly, since catches of one species will impact the natural growth not only of that species but of the others, as well. The objective of this paper is to develop a predator-prey model for two major species caught by the EU fishing fleet on European Union fishing grounds. The predator and prey’s population dynamics follow the Lotka-Volterra equation and are assumed to be logic-based, and a lineal interaction between the predator and prey populations is assumed. Optimal single owner multispecies fishery management is analysed, and the applied model is solved, obtaining the equilibrium value of biomasses, catches, and net benefits of the mixed fishery. The results show that the MSY of the predator is higher than that estimated by ICES, while MSY for prey is lower. The sensitivity analysis of the results reveals that the biomass levels of both species decrease as the discount rate increases, while catches increase.
文摘This paper examines the need for a return to a systemic,holistic,and normative approach to designing human settlements that has been neglected with the decline of the Welfare State and the shift to iecemeal,freewheeling,marked-based development during the unprecedented explosion of construction in the last thirty years.The need for a change is brought about by the current ecological and economic crises linked to a high degree to the current belief that the quality of cities emerges from the added-value of individual buildings or through the assemblage of individual structures put together like a building.This paper argues that a city is not like a building.The contemporary city is characterized by an unprecedented number of problems.These problems cannot be handled by individual good will or simple preventive or corrective actions by architects and developers as it has been done the last three decades.What is needed is an overall systemic framework of planning that ① is driven by normative criteria,② can handle a high degree of complexity and interdependence of factors,and ③ can deal with unanticipated,unintended,long-term irreversible environmental impacts that characterize the "third ecology," the inseparable complex of the natural and the human-made.
