Are Swimming Performance Data Relevant for Culvert Fish Passage?

Effective culvert fish passage depends, among other factors, on the fish swimming abilities and behaviour of the different sizes of migratory species.  This is particularly important for hydraulic conditions within the culvert barrel, as well as the outlet and inlet over the hydrological range which corresponds to periods of upstream fish movements.  Such hydraulic conditions include mean velocities, as well as distributions of velocities and turbulence, which vary with culvert shape and roughness (e.g. round corrugated or rectangular concrete), as well as nature-like morphodynamic designs, stream simulation techniques, embedment, or baffle type.  Field studies on culvert passage are limited and design usually relies on swimming performance data.  Hydraulic conditions within the barrel or at the inlet, may also block movements or affect passage efficiency over the range of discharges.  Optimum hydraulic conditions depend on how well-matched the swimming ability and behaviour of different species and sizes are with velocity and turbulence distributions within a culvert.  Field and laboratory studies on hydraulics and swimming performance have contributed to improved understanding of fish passage effectiveness.  Proper interpretation of such study results and more focused ecohydraulic studies are key to advancing effective culvert fish passage mitigation measures.