A tragedy of the commons case study: modeling the fishers-king crab system in Southern Chile

ZAMBRANO, ALAN; LAGUNA, FABIANA; KUPERMAN, MARCELO N.; LATERRA, PEDRO; MONJEAU, ADRIAN; NAHUELHUAL, LAURA

PeerJ

PeerJ

Año: 2023

2167-8359

Illegal fishing in small-scale fisheries is a contentious issue and resists a straightforwardinterpretation. Particularly, there is little knowledge regarding cooperative interactionsbetween ‘‘legal’’ and ‘‘illegal’’ fishers and the potential effects on fisheries arisingfrom these interactions. Taking the Chilean king crab (Lithodes santolla; commonname centolla) fishery as a case study, our goal is twofold: (i) to model the effectof illegal-legal fishers’ interactions on the fishery and; (ii) analyze how managementand social behavior affect fishery’s outcomes. We framed the analysis of this problemwithin game theory combined with network theory to represent the architecture ofcompetitive interactions. The fishers’ system was set to include registered (legal) fishersand unregistered (illegal) fishers. In the presence of unregistered fishers, legal fishersmay decide to cooperate (ignoring the presence of illegal fishers) or defect, whichinvolves becoming a ‘‘super fisher’’ and whitewashing the captures of illegal fishersfor a gain. The utility of both players, standard fisher and super fisher depend on thestrategy chosen by each of them, as well as on the presence of illegal fishers. The nodesof the network represent the legal fishers (both standard and super fishers) and the linksbetween nodes indicate that these fishers compete for the resource, assumed to be finiteand evenly distributed across space. The decision to change (or not) the adopted strategyis modeled considering that fishers are subjected to variable levels of ‘‘temptation’’ towhitewash the illegal capture and to social pressure to stop doing so. To represent thevital dynamics of the king crab, we propose a model that includes the Allee effect and aterm accounting for the crab extraction. We found that the super fisher strategy leadsto the decrease of the king crab population under a critical threshold as postulated in‘‘The Tragedy of the Commons’’ hypothesis when there are: (i) high net extractionrates of the network composed of non-competing standard fishers, (ii) high values ofthe extent of the fishing season, (iii) high density of illegal fishers. The results suggestthat even in the presence of super fishers and illegal fishers, the choice of properlydistributed fishing/closure cycles or setting an extraction limit per vessel can preventthe king crab population from falling below a critical threshold. This finding, althoughcontroversial, reflects the reality of this fishery that, for decades, has operated under a dynamic in which whitewashing and super fishers have become well established withinthe system.