Fishway Entrance Gate Experiments With Adult American Shad

Abstract:

A common problem among fishways is attraction and entry. Competing flows and complex hydraulics in and around the fishway can at times hinder passage and result in significant migration delays. The purpose of this study was to evaluate how flow conditions at a fishway entrance and the structural design of the entrance can affect entry. In most instances, a fishway entrance consists of a fully submerged hydraulic control (e.g. gate, weir) located at the downstream end of an open channel that guides fish to the main body of the fishway (e.g. lift, pool-and-weir). Changes to this hydraulic control design can influence the hydraulics (e.g. entrance jet velocity, flow pattern) and thus attraction and entry performance. To address these issues, a pilot study was performed in 2016 with upstream-migrating, adult American Shad (Alosa sapidissima) which documented the performance of a variety of hydraulic controls under a limited number of conditions. Water depth over the crest of the gate was shown to be the main driver in performance rather than gate design. Additional trials were completed in the spring of 2017 and demonstrated similar results. Water temperature also significantly affected fish performance in both years. The results of these studies provide guidance to state and federal resource agencies and the hydropower industry on methods to improve fishway attraction and entry rates.