Bull Trout Monitoring; Look Deep and Wide

Abstract

In most of the Bitterroot drainage fluvial westslope cutthroat (Oncorhynchus clarkii lewisi) trout are fairly common and fluvial bull trout (Salvelinus conftuentus) are rare. Monitoring the fluvial cutthroats is not difficult because mainstem population estimates are possible. However, due to the small number of fluvial bull trout, population estimates are not obtainable and redd counts are inconclusive. Monitoring of juvenile and resident populations also presents challenges. Population estimates (intensive) of bull trout that have the potential of providing quantitative data can be difficult to collect and basin-wide distribution (extensive) generally does not provide quantitative information. On the Bitterroot National Forest we have monitored bull trout and westslope cutthroat trout using mark-recapture population estimates for nearly 20 years. While these data allow us to follow trends within the reaches of a stream where populations are densest, it is not designed to identify trends in distribution. We have collected more extensive data but not in a systematic manner. We propose formalizing the collection of single pass electrofishing on short reaches throughout selected streams to augment the monitoring reaches established many years ago.