Short-Term Effectiveness of Constructed Barriers at Protecting Apache Trout

Abstract

Placement of fish migration barriers (primarily of gabion construction) on select streams is one of the major recovery actions used to isolate and protect upstream populations of Apache trout Oncorhynchus gilae apache from downstream populations of nonnative salmonids. However, the effectiveness of the recovery action has not been evaluated. We evaluated the success of constructed barriers at preventing upstream movement of nonnative salmonids into areas occupied by native Apache trout. We collected and marked salmonids downstream of six barriers on six streams in the White Mountains of east-central Arizona and subsequently electrofished upstream of the barriers to determine whether marked fish had moved past them. Only 1 of 1,436 marked salmonids was collected upstream of one of the six barriers evaluated over a 3-year period. Our results showed that the barriers evaluated in our study are effective for a short term; however, long-term evaluation is needed, as these failure rates represent minimum failure rates and they could increase as the number of years since barrier construction increases.