Common p-Beliefs in a Multi-species Commercial Fishery
Faculty of Fisheries and Marine Environment, Australian Maritime College, P.O Box 21, Beaconsfield, Tasmania, Australia 7270
Email: e.ngwenya@fme.amc.edu.au
Common p-beliefs occur when persons believe with a probability of at least p, that everyone believes with probability at least p that everyone believes an event with a probability of at least p, and so on. Persons hold common p-beliefs because of a prevalent event, known as a p-evident event, whose occurrence makes persons believe p-beliefs. In the limit common p-beliefs may converge to a 1-belief system, which is the equivalent of the notion of common knowledge. Fishers’ common knowledge in fishing decision-making is unlikely. At best, fishers achieve almost common knowledge. Given that fishing decisions are influenced by biological, environmental, social and economic variables, it is also likely that p-evident events exist and condition fishers to hold common p-beliefs. In this paper, indirect evidence of p-beliefs is gathered by finding p-evident events. Confidential commercial data from an Australia fishery are used. Common p-beliefs and p-evident events are assessed on the basis of fishers’ decision-making processes. Common p-beliefs are evaluated using a modified Markovian fleet dynamics model. Parameters of the modified Markovian models are evaluated. The results show (i) consistent ground and species choices, and (ii) reliable forecasts of participation. The results also show sensitivity to number of fishing grounds and length of fishing time. Given the significance of fishing time and number of grounds chosen by fishers, fishers’ p-beliefs and p-evident events must be considered in fishery management strategies.
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