Evaluating a Permeable‐Style Fish Barrier to Prevent the Upstream Recolonization of Nonnative Trout during an Eradication Project

Abstract

In the western United States, the introduction of nonnative Brook Trout Salvelinus fontinalis has had deleterious effects on native Cutthroat Trout Oncorhynchus clarkii subspecies, and often their populations must be controlled or removed if Cutthroat Trout are to persist. Man-made fish migration barriers are integral components of stream restoration projects, and typical designs are intended to be permanent and to funnel water over a drop and onto a splash pad. The water elevation drop and the splash pad, which prevents a jumping pool, are mechanisms intended to prevent fish from navigating upstream past the structure. In this study, we installed a temporary, permeable-style barrier that was designed to have water flow onto and through a horizontal, expanded steel panel. When fish attempted to move upstream, they would follow the water flow and end up underneath the barrier, with no opportunity to move further. The permeable barrier proved effective in preventing the upstream movement of Brook Trout, and additional advantages to this barrier style included straightforward permitting, low cost, ease of installation, and quick removal. The main disadvantage was the periodic cleaning (average of 7 trips/year) that was required to maintain its intended function. The permeable barrier separated stream reaches for 5 years, allowing biologists to (1) eradicate Brook Trout upstream through multiple-pass backpack electrofishing while preserving native Yellowstone Cutthroat Trout O. clarkii bouvieri and (2) apply a successful piscicide treatment below the barrier.