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J Theor Biol. 2018 Jun 14;447:1-11. doi: 10.1016/j.jtbi.2018.03.017. Epub 2018 Mar 13.

Competition or cooperation in transboundary fish stocks management: Insight from a dynamical model.

Author information

1
Faculty of Mathematics, Mechanics, and Informatics, Vietnam National University, Hanoi, 334 Nguyen Trai, Thanh Xuan, Hanoi, Viet Nam. Electronic address: hieunguyentrong@gmail.com.
2
Institut de Recherche pour le Développement (IRD), UMI 209, UMMISCO, IRD France Nord, Bondy, F-93143, France; Universityé Sorbonne Université, UMI 209, UMMISCO, Paris, F-75005, France.
3
Institut de Recherche pour le Développement (IRD), UMI 209, UMMISCO, IRD France Nord, Bondy, F-93143, France; Universityé Sorbonne Université, UMI 209, UMMISCO, Paris, F-75005, France; Université Cheikh Anta Diop, UMI 209, UMMISCO, Dakar, Senegal.
4
Faculty of Mathematics, Mechanics, and Informatics, Vietnam National University, Hanoi, 334 Nguyen Trai, Thanh Xuan, Hanoi, Viet Nam.
5
Institut de Recherche pour le Développement (IRD), UMR 195 Lemar, Hann, Dakar BP 1386, Senegal; Institut Sénégalais de Recherches Agricoles (ISRA), Centre de Recherches Océanographiques de Dakar-Thiaroye, PRH, Dakar, BP 2241, Senegal (g)Institut de Recherche pour le Développement (IRD), Délégation Régionale France Ouest, UMR Lemar, Campus Ifremer; BP 70, Plouzané 29 280, France; Institut de Recherche pour le Développement (IRD), Délégation Régionale France Ouest, UMR Lemar, Campus Ifremer; BP 70, Plouzané 29 280, France.

Abstract

An idealized system of a shared fish stock associated with different exclusive economic zones (EEZ) is modelled. Parameters were estimated for the case of the small pelagic fisheries shared between Southern Morocco, Mauritania and the Senegambia. Two models of fishing effort distribution were explored. The first one considers independent national fisheries in each EEZ, with a cost per unit of fishing effort that depends on local fishery policy. The second one considers the case of a fully cooperative fishery performed by an international fleet freely moving across the borders. Both models are based on a set of six ordinary differential equations describing the time evolution of the fish biomass and the fishing effort. We take advantage of the two time scales to obtain a reduced model governing the total fish biomass of the system and fishing efforts in each zone. At the fast equilibrium, the fish distribution follows the ideal free distribution according to the carrying capacity in each area. Different equilibria can be reached according to management choices. When fishing fleets are independent and national fishery policies are not harmonized, in the general case, competition leads after a few decades to a scenario where only one fishery remains sustainable. In the case of sub-regional agreement acting on the adjustment of cost per unit of fishing effort in each EEZ, we found that a large number of equilibria exists. In this last case the initial distribution of fishing effort strongly impact the optimal equilibrium that can be reached. Lastly, the country with the highest carrying capacity density may get less landings when collaborating with other countries than if it minimises its fishing costs. The second fully cooperative model shows that a single international fishing fleet moving freely in the fishing areas leads to a sustainable equilibrium. Such findings should foster regional fisheries organizations to get potential new ways for neighbouring fish stock management.

KEYWORDS:

Aggregation of variables; Fisheries management; ODE; Pelagic; Shared fish stock; West Africa

PMID:
29548735
DOI:
10.1016/j.jtbi.2018.03.017
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