A simple method to predict regional fish abundance: An example in the McKenzie River Basin, Oregon

Abstract

Regional assessments of fisheries resources are increasingly called for, but tools with which to perform them are limited. We present a simple method that can be used to estimate regional carrying capacity and apply it to the McKenzie River Basin, Oregon. First, we use a macroecological model to predict trout densities within small, medium, and large streams in the McKenzie Basin. Next, we evaluate the reliability of the predicted trout densities by comparing them with field-measured densities. We then calculate the total surface areas of small, medium, and large streams within the basin and multiply these surface areas by the predicted trout densities to estimate regional carrying capacity. Predicted carrying capacity within the basin is approximately 2.1 million trout (median predicted abundance). Our method requires minimal input data, and much of this data can be compiled from literature sources. The method may therefore have broad utility.