Limitations on the Application of Swimming Performance Estimates to the Design of Culverts for 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. Field studies on
culvert passage are limited and design usually relies on estimates from fish
swimming performance data. Such data though are usually collected in fairly
uniform flow conditions in swim chambers or volitional open channels and
complete data sets are limited to just a few species; yet optimum passage
conditions depend on how well-matched the swimming ability and behaviour of
different species and sizes are with velocity and turbulence distributions within
culverts. Proper interpretation of behaviour, speed, endurance and swim
distance estimates of different size fish to culvert hydraulics is rather
challenging. Limitations of swimming performance estimates and hydraulics on
culvert passage are outlined.