The effects of measurement uncertainty on spatial characterisation of recreational fishing catch rates

Abstract

Accurate mapping of catch rates of fish species is important for identifying their abundances and locations, and for monitoring their population changes. However, the use of imprecise fishing survey data may influence mapping and delineation of locations with high catch rates. We evaluated the incorporation of measurement uncertainty in recreational catch rate data for three important recreational fish species with different behavioural and distributional characteristics. The study combined a soft indicator kriging approach that uses a logistic function transformation and p-field simulation to determine the effect of measurement uncertainty on catch rate mapping and fishing area delineation. The results suggest that measurement uncertainty can influence the degree of spatial autocorrelation and the precision of kriging estimation. In addition, measurement uncertainty was found to influence the probability of classifying a location as either being a high or low catch rate zone. In general, the incorporation of the measurement uncertainty improves the ability to draw valid conclusions about the estimation results, which may influence any decision regarding the delineation of areas of abundance for spatial management. The use of a soft indicator kriging approach is a promising tool for catch rate mapping, in particular for survey data with class-specific patterns of spatial continuity.