时间：2024年4月29日（周一）14:00-15:00

Time：14:00-15:00, Monday, April 29, 2023

地点：西湖大学云谷校区E4-233 & ZOOM

Venue: E4-233, Yungu Campus & ZOOM

ZOOM ID: 929 1481 0776

PASSCODE: 068737

主讲人/Speaker: Simone Scotti, University of Pisa

主讲人简介/Biography: Simone Scotti was born in Italy and graduated from Ecole Normale Superieure (Paris, France) with a bachelor in physics and a master in applied mathematics in 2005. He defended his PhD at Scuola Normale Superiore in 2009 under the direction of Nicolas Bouleau. He held a temporary post-doc at Ecole Polytechnique Federale de Lausanne and then worked as assistant professor at Université Paris VII. He obtained his habilitation as full professor in 2017. In 2022 he joined the University of Pisa as associate professor after an international selection. He currently works on applied probability and control theory with applications straddling economics, finance, and biology.

讲座主题/Title: The dilemma between fishes' population conservation and harvest: Optimal policies in presence of no-take area and decimations

讲座摘要/Abstract: 

Persistence in the literature is the perception of an inherent tradeoff between ecological conservation and economic harvesting goals. Overexploitation may lead to resource destruction, including extinction. Conservation measures should be decided and implemented. A standard ecological response is to impose no-take areas or marine reserves. This presentation is based on two different but related problems. First objective is to study a harvesting management problem under the constraints of a no-take area, which we formulate mathematically as a bi-dimensional singular stochastic control problem. Using dynamic programming theory, we characterise our value function as the unique solution to a Hamilton-Jacobi-Bellman equation. We also describe the optimal harvesting strategy by identifying the harvesting and non-harvesting regions. We show that setting up reserve area not only leads to a better ecological conservation but may also increase the economic benefit for fishing industry in the long run. We further enrich our studies with some numerical analysis, enabling us to get some insightful understanding on the size of the reserve area where no-take policy should be implemented.

In a second part, we focus on the case of arrival of decimations remarking that they may occur in clusters. We model this clustering phenomenon using marked-Hawkes processes coupled with the so called logistic branching SDE. We characterise our value function as the unique solution to a HJB inequality. We describe the optimal harvesting strategy by identifying the harvesting/non-harvesting regions. We obtain counterintuitive results which go against the generally accepted belief that when facing increasing decimation risk due to disasters, the optimal harvesting policy should lead to a decrease in harvesting activity. These results point to insightful understandings about the deep frailty of fish resources that could explain the collapse of fishery industries in Northwest-Atlantic. Governments and international authorities have to take actions against the cause of disasters such as pollution or overexploitation of water resources to reduce the risk of the recurrence of fish decimation as well as to better define and evaluate the real cost of marine resources extinction.