Model simulations to determine optimal fishing effort and season duration for a tropical shrimp fishery

Kuwait's shrimp fishery presents typical tropical shrimp fishery characteristics with highly variable recruitment, fast growth and strong seasonal patterns. Both the General Production Model and Age-structured Model were chosen to assess the stock status of the Kuwait's shrimp fishery. The estimated Maximum Sustainable Yield(MSY) was 2 518 metric ton(t) with a corresponding fishing eff orts( f MSY) 7 265 standard boat-days from the General Production Model. Similar results from the Age-structured Model were 1 936 t and 6 449 boat-days respectively. Comparing these results with the average annual shrimp landings(1 772 t) and average fishing eff ort(9 710 boat-days) in the past 10 years, we concluded that the fishery was overfished. Model simulations to show the changes of recruitment, biomass and possible catch under different fishing eff ort scenarios indicated possible stock collapse if the fishing eff ort continually increase. But both shrimp recruitment and biomass will increase if the current fishing eff ort is reduced. Model simulations also showed a possible increase of MSY by delaying the opening or by closing the season earlier. Based on these results, recommendations to improve the management of Kuwait's shrimp fishery are presented.

Optimal effort,fish farming,and marine reserve in fisheries management

In this paper,we develop a bioeconomic model to determine an optimal wild catch harvest and freshwater commercial aquaculture production in a lake that uses cages or floating rafts.Although off-bottom aquaculture activities have less impact on the environment compared to on-bottom aquaculture,it has negative externalities.It takes away the fishing area and hence creates pressure in the open-access fishing ground.It also changes the nutrient and ecological composition of the environment.We recommend the implementation of a reserved area to minimize the impact of fishing and aquaculture activities.The reserve also helps in improving the habitat and restocking the fish population which is declining rapidly.We determine the optimal sizes of the aquaculture and reserve and the optimal effort level that maximizes social welfare.We illustrate our findings using numerical simulations and perform an analysis of the optimal solutions with respect to biological and economic parameters involved in the model.

Cooperative differential games guidance laws for multiple attackers against an active defense target

This paper is concerned with a scenario of multiple attackers trying to intercept a target with active defense.Three types of agents are considered in the guidance:The multiple attackers,the target and the defender,where the attackers aim to pursuit the target from different directions and evade from the defender simultaneously.The guidance engagement is formulated in the framework of a zero-sum two-person differential game between the two opposing teams,such that the measurements on the maneuver of the target or estimations on the defending strategy of the defender can be absent.Cooperation of the attackers resides in two aspects:redundant interception under the threat of the defender and the relative intercept geometry with the target.The miss distances,the relative intercept angle errors and the costs of the agents are combined into a single performance index of the game.Such formulation enables a unitary approach to the design of guidance laws for the agents.To minimize the control efforts and miss distances for the attackers,an optimization method is proposed to find the best anticipated miss distances to the defender under the constraint that the defender is endowed with a capture radius.Numerical simulations with two cases are conducted to illustrate the effectiveness of the proposed cooperative guidance law.