Research

Bataille, G. (2024). An explicit solution to harvesting behaviors in a predator-prey system. Natural Resource Modeling, e12408.

Abstract : This paper derives closed-form solutions for a strategic, simultaneous harvesting in a predator-prey system. Using a parametric constraint, it establishes the existence and uniqueness of a linear feedback-Nash equilibrium involving two specialized fleets and allow for continuous time results for a class of payoffs that have constant elasticity of the marginal utility. Theses results contribute to the scarce literature on analytically tractable predator-prey models with endogenous harvesting. A discussion based on industry size effects is provided to highlight the role played by biological versus strategic interactions in the multi-species context.

Keywords :  Common-pool Resource, Dynamic games, Fisheries, Predator-prey relationship

Partial Considerations of a Predator-Prey Ecosystem, with H. Stahn and A. Tomini. 

Abstract : This study presents new insights into the exploitation of a predator-prey ecosystem. It examines the emergence of biological externalities when agents specialize in harvesting specific fish types and only partially consider the dynamic of the ecosystem.  We contrast this regime with the socially optimal outcomes. Specifically, private agents overestimate the conservation value of the targeted species and limit their fishing effort. This induces predator overpopulation and the depletion of the prey stock. This global under-fishing persists even given agents’ strategic interactions among themselves when targeting the same fish. Finally, we propose a species-specific instrument to regulate the two main inefficiencies: strategic and biological externalities. 

Keywords :  Fisheries, Biological externalities, Prey-predator relationship, Optimal control.

Breaking the Net: The Fragility of Cooperation in Shared  Fisheries, with B. Zou. 

Abstract : This study investigates the instability of fishery management organizations using a dynamic multistage optimal control model with two heterogeneous countries exploiting shared fishery resources. Motivated by recent cases of coalition breakdowns, we analyze the transition from cooperation to competition, driven by differences in time preferences and the use of fixed sharing rules for joint payoffs. Our findings show that no static sharing rule— even when optimally chosen at the time of coalition formation—can sustain cooperation over time. Despite this instability, we identify the sharing rule that maximizes coalition duration and provide sufficient conditions for the identity of the first existing player. The outcome depends heavily on the initial allocation of payoffs and the degree of heterogeneity in discount rates. Specifically, higher differences in discount rates decrease the overall coalition duration. To address these challenges, we propose a time-dependent sharing mechanism for the coalition's total worth that ensures fairness at every point in time. Under this scheme, no player has an incentive to revise their membership over time.

Keywords :  Fisheries, Fishery Management Organizations, Dynamic Games, Multistage Optimal Control.

Managing Predator-Prey Fisheries with Prey Refuges. (Job Market Paper)

Abstract :  Many natural and artificial marine habitats are designed to provide refuge for certain species by reducing natural predation. While the primary objective of prey refuges is to promote marine biodiversity, their economic implications remain underexplored. This paper develops a tractable two-species predator-prey model with specialized and strategic harvesting to assess the impact of prey refuges on the efficiency and sustainability of multi-species fisheries. It is shown that prey refuges reduce fishing pressure on both prey and predator populations. Beyond directly enhancing economic gains in the prey fishery by mitigating natural predation, refuges can also generate spillover benefits for the predator industry by increasing prey availability outside the protected area. I characterize the conditions under which a regulator maximizing total industry welfare can implement an artificial prey refuge to optimally manage predation intensity. Since refuges take time to generate ecological and economic benefits through population dynamics, discounting plays a critical role in determining its optimal size. Even when the regulator sets harvesting quotas optimally across industries, an artificial refuge is an effective tool to manage natural predation. Finally, I use data from predator-prey interactions in Lake Victoria fisheries to support the theoretical findings.

Keywords :  Prey refuge, Predator–prey interactions, Common-pool resources, Externalities, Differential games

Les refuges pour proies : une nouvelle méthode de gestion de la pêche?, The conversation, 2024.