A Simple Empirical Model of Data Fouling by High-Grading in Capture Fisheries

A serious problem facing fisheries managers is how to improve estimates of the distortion in stock assessments resulting from "fouling" of commercial catch data. We propose a simple analytical model of discarding and high-grading, and estimate the "data fouling factor"—the wedge between what is caught and discarded at sea, and what is reported to the regulator. Using available data on biology, harvesting technology, prices, and costs, the model is parameterized and solved numerically for the profit-maximizing effort level and the associated number of high-grading operations. Some illustrative policy implications are derived.