INFERRING A BIOPOLITICAL CONSENSUS VIEW OF STOCHASTIC DYNAMICS FOR MANAGEMENT OF A TRANSBOUNDARY FISHERY

ABSTRACT. Management of trans‐boundary fisheries is a complicated problem with biological, legal, economic and political implications. We propose a simple stochastic differential‐equation model to describe a biopolitical consensus view of fish stock dynamics. Estimates of the drift and diffusion terms of three stochastic differential equations are obtained using data from the southern bluefin tuna (SBT) fishery with a method based on the Kolmogorov‐Smirnov statistic. We refer to these estimated equations as alternative biopolitical consensus views of SBT stock dynamics. Each of these is used to generate a time series of optimal harvest that achieves the objective of maximizing the present value of expected fishery returns. These time series of optimal harvests are then compared to actual harvests for the period 1981 1997.     

Property appraisal with a log - t predictive distribution

A multiplicative model with log-normal errors is used to appraisethe market value of a property and a natural conjugate prior,describing the beliefs of an expert appraiser about the parameters,is elicited. Loss is an asymmetric function of the predictedprice as a proportion of the actual price, and the optimal predictionis a multiplicative adjustment to the exponent of the predictivemean of the logarithm of price. The prediction of the priceof a property is made using both the elicited prior and tworeference priors. The robustness of the procedure is assessedby means of the evaluation of a number of elasticities of priceprediction with regard to changes in a parameter value, eitherof the prior distribution or the loss function.