Throwing Away 50 Years of Laboratory Results: What Recent Data on Volitional Swimming Performance Tell Us about Predicting Passage through Velocity Barriers

When Brett first developed the protocols for measuring swimming performance in 1964, a primary goal was to develop velocity criteria for turbine intakes.  Since then his techniques for U_crit and fixed velocity tests have been widely repeated and have formed the basis for design of fishways and road crossings.  The biology underlying many of these design standards is surprisingly weak, however, and has strayed far from Brett’s original intentions.  Furthermore, work at a number of laboratories using a range of techniques has shown that Brett’s methods radically underestimate swimming abilities of free-swimming fish at sustained, prolonged, and sprint speeds.  These new data not only challenge our understanding of what fish are capable of in terms of speed and endurance, but they also demonstrate that behavioral strategies for overcoming velocity challenges are at least as important in driving passage success as physiology.