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

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.