Session C6: Efficiency of a Horizontally and Vertically Oriented Studded Fish Pass Substrate for Upstream Moving European Eel (Anguilla anguilla) and River Lamprey (Lampetra fluviatilis)

Abstract: For diadromous anguilliform fish, such as eel (Anguilla spp.) and lamprey (Petromyzon spp. and Lampetra spp.), conventional fishways function poorly. Often this is a reflection of their alternate life history strategies and/or poor swimming performance in comparison to subcaragiform species, for which fishways are more frequently designed. Unique behavioural strategies adopted by anguilliform fish during upstream migration (such as climbing) provide an opportunity for the development of novel, species specific solutions. For eel, synthetic bristle board passes have been developed and widely implemented. More recently, boss or studded substrates (commonly referred to as eel or lamprey tiles in the UK) have been installed oriented either horizontally (with upward facing studs) or vertically (and side mounted with studs facing the channel wall) at numerous low-head barriers. Despite implementation in the field, here we will present results from the first controlled study on the efficiency of eel/lamprey tiles. Using a large open channel flume we were able to quantify passage success, passage efficiency and observe the behaviour of yellow phase European eel (Anguilla anguilla) and upstream migrant adult river lamprey (Lampetra fluviatilis) as they encountered a model crump weir. The weir was either unmodified or modified with horizontally or vertically oriented tiles. The addition of the tiles improved passage; however efficiencies remained low in some instances, particularly for lamprey. Potential causes for poor passage are discussed, as is the need for further research on design optimisation, which if conducted may enable eel/lamprey tiles to significantly improve the connectivity of rivers fragmented by anthropogenic barriers