環境不確定下之海洋保護區長期均衡的模擬評估

The Simulation of a Long-term Equilibrium to MPAs under Environmental Uncertainties

海洋保護區是一種漁業資源保護的概念，透過完善的棲息地保護，給予魚群存量穩定的回復效果，此外也能提供學術以及觀光效益。過去許多文獻顯示建立海洋保護區在增加魚群存量上之效果優於傳統上的漁業管理，但面對著海洋環境愈來愈不確定下，長期均衡下海洋保護區是否依舊是一種有效的管理工具，乃是本文研究的重點。 本文模型將海洋劃分為兩區域，一為可捕獲區，漁民可在此區進行捕獲活動；另一區則為保護區，保留原本棲息地原貌，利用原生環境促進魚群存量生長，透過溢出效果增進可捕獲區之捕獲率。另外，在利潤極大化以及開放式漁場模型中，加入海底環境以及捕撈方式等因素及環境上的不確定性因子，文中探討在捕獲率外生化下漁民捕獲之效益變化。 研究結果顯示，在利潤極大化模型底下，雖然魚群存量會隨著保護區面積增加而趨減，但是仍然處於永續經營。此外，即使在面對環境不確定性因素影響，隨著保護區面積增加，長期均衡下仍能達到穩定漁民捕獲量的效果。接著研究結果顯示，在公開漁場模型裡，當捕獲率是為外生變數，若保護區面積夠大，在面對各種不確定性以及捕獲率情況下，長期均衡時，魚群回復能力都優於面積較小的保護區。

 

To effectively manage fishery resources, many studies suggest that the establishment of marine protection reserves (MPAs) lead to higher fishery yields than conventional management. The idea of MPAs is to allow fish stock to rebuild by creating a comprehensive protection for its habitat. It also yields benefits in terms of tourism and academic research. However, under the increasing uncertainty of marine environments, it is worthy to investigate whether MPAs still serve as a long-term optimal equilibrium of resource management and protection. The model in this study divides the marine environment into two areas: a fishing zone and a no-take zone, in which all fishing and extraction are prohibited. The latter preserves the original habitat, promotes the growth of fish stocks, and helps increase fishery yields in the fishing zone through spillover effect. Also, this study investigates the effects of environmental uncertainty on the profit maximization model and the open access model, along with the impacts of treating exploitation rate as an exogenous variable. Simulation results suggest that although fish stock will decrease with the increase of MPA sizes in the profit maximization model, the resources are still sustainable. Also, the increase of MPA sizes can stabilize the fishery yield in the long-run equilibrium even with uncertainty in the environment. In the open access model with exploitation rate treated as an exogenous variable, the results show that under all scenarios of uncertainty and exploitation rate, the fish stock rebuild better when the size of the protected area is at a high level in the long-run equilibrium.