Catch-Per-Unit-Effort: A Statistical Model for Pacific Halibut (Hippoglossus stenolepis)

The empirical distributions of catch-per-unit-effort (CPUE) of Pacific halibut (Hippoglossus stenolepis) were positively skewed and could be modeled by a general family of distributions involving power transformations. The root normal distribution, a special case from the family, was found to be a convenient model for the data. Measures of the central tendency and variance of the distribution were derived. Estimators of the central tendency based on increasing variance of a function of catch as a function of effort were most appropriate for the data. A median-based estimator performed better than a mean-based estimator. Thus, statistical modeling of CPUE provided a tool for constructing a better estimator of an abundance index.