Poster Presentation International Conference on River Connectivity (Fish Passage 2018)

Determining fish passage solution success for river-resident brown trout; the importance of ‘before’ data and understating the influence of flow, fish size and translocation. (52939)

Jon D Bolland 1 , Jamie R Dodd 1 , Ian G Cowx 1
  1. University of Hull International Fisheries Institute (HIFI), Hull, YORKSHIRE, United Kingdom

Man-made, physical barriers have disrupted longitudinal connectivity for fish in many river systems throughout the world for centuries. To date, most research has focused on remediation measures to ease movement of anadromous salmonids past such barriers. Indeed, little research has examined their efficacy for river-resident fish, which may be less motivated to move, require passage over a wider range of flows and smaller than anadromous counterparts, especially at low-head structures that may not be a complete barrier to fish movement. Passive Integrated Transponder (PIT) telemetry was used to assess the upstream-directed movements of river-resident brown trout into and through three fish passes in northern England. A LCB fish pass significantly improved overall passage efficiency from a maximum of 64% before construction to 91% after. In addition, there was a significant decrease in delay at the obstruction after the LCB fish pass was constructed and fish passed on a greater range of flows (Q4 – Q93) in comparison to before (Q34.5 – Q16.5). Attraction (51%), entrance (86%), passage (78%) and exit (97%) efficiencies were high in the nature-like bypass channel, and trout of a wide range of sizes entered and exited the pass across a wide range of flows (entrance = Q2 - Q97 and exit = Q13 - Q93). At another LCB fish pass, more fish displaced from upstream approached (76%), entered (59%) and ascended (95%) in comparison to resident trout caught below the weir (29%, 14% and 100%, respectively). The size of fish that approached the weir and the time between release and first approach to the weir were similar for displaced and non-displaced fish but the influence of fish length on fish pass entry was highly significant. The main lessons learned during these investigations will be discussed in relation to defining a successful fishway for river-resident fish.