Author(s): James A. Harvey; Vincent S. Neary; Hayden Mattingly
Linked Author(s): Vincent Neary
Keywords: No Keywords
Abstract: The predictive performance of exhaustion-threshold (ET) curves was examined for western mosquitofish (Gambusia affinis) and the Barrens topminnow (Fundulus julisia) under volitional swimming conditions for three culvert flow regimes. The ET curves were previously developed using standard protocols based on fixed velocity swimming endurance tests. As plots of mean flow velocity versus passage-barrier length, these curves ideally predict the threshold condition for passage of a given species in a culvert. The culvert is assumed to be a barrier to fish passage when ordinates, based on these parameters, fall above the ET curve and to allow passage when ordinates fall below the curve. In this study passage was reported for both species. Sixteen trials for each species were conducted and passage was monitored for 240 topminnows (29.0-89.8 mm total length) and 238 mosquitofish (31.7-56.9 mm total length). Three outlet control culvert flow regimes were considered: a fully pressurized pipe flow, a drawdown (M2) flow profile, and a backwater (M1) flow profile. For all three culvert flow regimes, the mosquitofish ET curves successfully predicted passage and exclusion for 93.4% and 90.0% of the fish, respectively. For the pressurized and drawdown flows, the ET curves successfully predicted exclusion for 91.7% and 78.3% of the fish, respectively. For the backwater flow, they successfully predicted outright (100%) exclusion. For all three culvert flow regimes, the topminnow ET curves successfully predicted passage for 71.7% of the fish. Successful passage was predicted for 65.2%, 73.2%, and 77.1% of the fish for the pressurized, drawdown, and backwater flow, respectively. This study suggests that ET curves can provide reasonable predictions of fish passage despite differences between fixed and volitional swimming conditions and the common disregard for spatially non-uniform local flow conditions. It supports the application of ET curves as passage screens in regional culvert assessments for the species tested.
Year: 2009