Crookes, Douglas2016-05-262016-05-262016-03Crookes DJ. Trading on extinction: An open-access deterrence model for the South African abalone fishery. South African Journal of Science. 2016 ; 112(3/4), Art. #2015-0237, 9 pages. http://dx.DOI.org/ 10.17159/sajs.2016/20150237.0038-2353 (print)1996-7489 (online)10.17159/sajs.2016/20150237http://hdl.handle.net/2263/52762This article forms part of a 3-year project studying new approaches to model the economics of scarce resources.South African rhinoceros (e.g. Diceros bicornis) and abalone (Haliotis midae) have in common that they both are harvested under open-access conditions, are high-value commodities and are traded illegally. The difference is that a legal market for abalone already exists. An open-access deterrence model was developed for South African abalone, using Table Mountain National Park as a case study. It was found that illegal poaching spiked following the closure of the recreational fishery. The resource custodian’s objective is to maximise returns from confiscations. This study showed that a legal trade results in a ‘trading on extinction’ resource trap, with a race for profits, an increase in the probability of detection after a poaching event and the depletion of populations. In contrast with HS Gordon’s seminal article (J Polit Econ 1954;62:124–142), profit maximisation does not automatically improve the sustainability of the resource. Under certain conditions (e.g. a legal trade with costly enforcement), profit maximisation may actually deplete abalone populations. The article also has implications for rhino populations, as a legal trade is currently proposed.en© 2016. The Author(s). Published under a Creative Commons Attribution Licence.RhinoSystem dynamicsIllegal harvestingPredator–preyTable Mountain National ParkSouth African abaloneSouth African rhinocerosArticle