Optimal Harvesting Of Aquaculture Systems In Toxin Or Pest Environment

Since the 1960's,with the diversified development of control theory,it is entering a new stage on the breadth and depth.Control theory is widely used in transportation,biological control,environmental protection,etc..Biological system is a typical complex nonlinear system.There are,so far,some researches on the dynamical behavior and con-trol problems about the biological system,which have achieved some outstanding results.However,plenty of problems are waiting to be dealt with.As the degree of industrializa-tion,environmental pollution is serious,the optimal control problem of ecosystem in the pollution environment becomes a hot issue of concern.With the background of aquaculture,the mathematical models are built in this disser-tation.The optimal harvesting problems are discussed in toxin or pollution environment.The stability and boundedness of ecological systems are discussed in according to the actual situation of breeding in finite-time.While capture and the elimination of the toxin be carried out simultaneously,an optimal harvesting method is made.The main work is as follows:(1)The issue on the optimal harvesting of fish catching after eliminating toxin during the fish aquiculture is studied.Taking the aquiculture of bighead carp and silver carp as an example,considering the characteristics of the growth and the reproduction of prymnesi-acee,and taking prymnesiacee toxin as the pollutant source,an optimal harvesting model of fish aquiculture is built.The finite-time stability of the system is discussed.While the fish aquiculture and the elimination of the algae toxin targeted as pollutant source can be carried out simultaneously,an optimal harvesting method is made,from which a general algorithm of the optimal harvesting solution can be obtained.(2)The optimal guaranteed cost control problem of a single specie bio-economic sin-gular system in algae environment is discussed,where fuzzy method is applied.The real world case introduced is set on the aquaculture of whitebait in algae environment,based on which a class of non-linear bioeconomic models are established.In these models,the time period is finite and the biomass is controlled under certain range.In order to achieve the particular range at the least cost in a finite-time,a guaranteed cost controller is de-signed based on fuzzy model in this paper.In addition,a practical example is carried out to illustrate the feasibility of the designed controller.(3)The optimal guaranteed cost control problem of a single species model with stage structure is studied by fuzzy methods.The non-linear harvesting model in a toxic en-vironment is established,and the toxin considered has the characteristics of growth and reproduction.Furthermore,for the reason of practical problems,in which the period of production is a finite time and the biomass and toxin should be controlled into some range,the guaranteed cost controller is designed based on fuzzy models.While controlling the biomass concentration achieved the specified range,the controller eliminated the toxin entirely or controlled the toxin in traces concentration according the actual demand of d-ifferent environment.Finally,a practical example is carried out to illustrate the feasibility of designed controller in the case of non-toxin and traces of toxin,respectively.(4)Symbiosis is the beneficial relationship between the different two or three close contact creatures,and there are many kinds' forms of the symbiosis.Mixed feeding based on symbiosis relationship is usually used by farmers to protect the water quali-ty,increasing the income,and etc..Taking the lobster and the lotus root aquiculture in the aphids environment as background,symbiotic biological growth model is built.The balance of ecological environment and finite-time stability of the system are discussed.While the lobster and the lotus root aquiculture and the elimination of the aphids can be carried out simultaneously,an optimal harvesting method is derived,from which a general algorithm of the optimal harvesting solution can be obtained.