| Hi everyone The Fish Passage Action Team have been working on a simple one-page guide to help with the remediation of common structures causing a barrier to fish. The guide includes a link to an interactive decision tool and some helpful before & after examples. Happy holidays! |
 Fish Passage Remediation (existing structures) Overview Fish passage remediation is less about target species, specific swimming speeds, average velocities, Mannings numbers etc., and more about understanding the medium in which fish have evolved to navigate, i.e. water, with the dynamics of complex flows and boundary layers all at a fine resolution. Basic principles – “Match or better” the streamflow characteristics. – Provide complex flows (non-laminar) – multi-directional flows with rest pools. – Length of fast flow zones between rest pools must be shorter than fish burst-swim capabilities. – Provide sufficient depth. – Ensure continuity – no overhangs. – Give fish a range of navigation path options. – Ideally, retain bed material. General rules. – Rope should not be used in culverts if baffles can be fitted, even if climbing species are targeted. – Ramps should include splash zones and substrate, e.g. rope. – Ramps should extend into the plunge pool as far as practicable. – Baffles should be spaced so that the rest pool from one extends easily up to the next. – Baffles may be considered artificial bed material in some situations, i.e. create similar hydrological conditions – If rope is fitted through a culvert that is also perched, a second set of rope should be fitted at the outlet. – Rope should only be attached at the upstream end. – Interventions should not significantly reduce culvert capacity or increase the risk of debris jams. – Tide-gates should be designed/modified to delay the closing as long as possible. Which tools to use where? The above principles help to guide us towards selecting appropriate remediation tools. For more detailed guidance on the use of remediation tools click here: Remediation Decision-Tree Interactive Tool Before & after examples click here:https://www.ats-environmental.com/before-after-remediation/ Measures of success: Success should be outcome-focused and easy to measure or observe. – Complex flows similar to stream (depth, width, velocities) – Bed material retained. – Continuity – no perch or overhang. – Extended opening period for tide gates. Please note that the linked resources above are kindly provided by ATS Environmental. |
