Effects of interlocked carpet ramps on upstream movement of brown trout Salmo trutta in an upland stream

Abstract This paper assesses the extent to which Interlocked Carpet Block Ramps (ICBRs) impede the upstream movement of brown trout Salmon trutta (L. 1758). It presents model simulations of hydraulic conditions across an ICBR of the type used widely for energy dissipation in high gradient rivers. Model simulations were related to published hydraulic suitability criteria for upstream movement of fish to assess the usability of individual routes, connectivity between routes and whether routes were available to allow upstream passage across the whole ramp. Results suggest that connected routes were available at most of the simulated discharges. Nevertheless, higher and lower discharges appeared to impose constraints, due to swimming ability and minimum useable water depths, respectively. Precise patterns of hydraulic suitability and connectivity of potential routes at different discharges varied appreciably between simulations using the different hydraulic criteria.