Development and application of an agent-based model to evaluate methods for estimating relative abundance indices for shoaling fish such as Pacific rockfish (Sebastes spp.)

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Authors James T. Thorson, Ian J. Stewart, André E. Punt
Journal/Conference Name ICES Journal of Marine Science
Paper Category
Paper Abstract Many marine fish, including Pacific rockfish (Sebastes spp.), exhibit habitat-selective and shoaling behaviours, which can lead to imprecision when using survey data to estimate an annual index of stock abundance. We develop a spatial agent-based model (ABM) for Pacific rockfish, which generates data similar to those observed in existing bottom-trawl surveys and can represent various spatial and shoaling behaviours. We use the ABM to evaluate the performance of a model that uses mixture distribution methods to account for fish shoals and delta-methods to account for range expansion or contraction. This delta-mixture model is compared with conventional delta-generalized linear models (delta-GLMs) and a quantile regression delta-model. The delta-mixture increases precision by 15% relative to delta-GLMs in estimated abundance indices when shoaling behaviours are present, whereas precision is similar between delta-GLM and delta-mixture models when shoals are absent. The delta-quantile method has similar improvements over conventional delta-GLM methods, and the improved precision from delta-mixture and delta-quantile methods is decreased but not eliminated by decreased sampling intensities. These simulations represent the first evaluation of delta-mixture models for index standardization and show a substantial improvement over conventional delta-GLMs for shoaling species such as Pacific rockfish.
Date of publication 2012
Code Programming Language R

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