The Behavioral Mechanics of Barriers: A Movement-Theoretic Approach

Too often attempts to pass fish at dams or road crossings fail to meet performance expectations.  Passage through engineered structures is often poor, and dam removals and stream simulation solutions can be expensive and slow, diverting resources that might be spent more efficiently on simpler solutions.  Advocates for dam removal often promise that improved fish passage will be an inevitable result, but data to support these claims are scarce.  Part of the problem with underperforming structures and solutions comes from unrealistic expectations of passage performance.  Performance metrics based on rates of movement are at once biologically defensible, and also provide engineers with the information required to optimize design.  These rates can be comprehensively defined in units of distance/time (velocity) or %/time (diffusion).  Theoretical and empirical data demonstrate the application of this approach, which could form the foundation for a universal framework of performance standards for passage at both engineered and natural barriers.