Abstract Manager

The ability of fish to pass through watercourse crossings, particularly through culverts, is a function of specific variables, including the hydraulic conditions in the culvert, fish swimming abilities, and motivation of the individual often driven by species life history strategies. Culvert designs (i.e., length, width, slope, bottom type) affect the hydraulic and light conditions at the crossing location. Fish swimming ability is a function of the biometrics (e.g., size, form, and muscle tissue type) that affects both swimming speed and endurance. Motivation is a function of the type of purpose of the movement (e.g., migration to access spawning areas). Fish species who rely on migrating to specific spawning areas are more susceptible to impacts from watercourse crossings that affect fish passage, while populations of resident species may be less so.

Culvert length, which has received less attention as a specific design parameter, will become increasingly important as roads are upgraded to accommodate wider transportation corridors and as existing long culverts are slated for replacement or refurbishment. How many fish moving through a culvert should be considered adequate to maintain population viability? How important is lighting? How does this relate to the species inhabiting a watercourse? How should we determine benchmarks for adequacy in fish passage rates through culverts to determine whether there has been a harmful alteration, disruption and destruction (HADD) to fish and fish habitat? While a culvert results in change to fish habitat, not all change is necessarily adverse to all species. This presentation provides a jurisdictional review of culvert design criteria with particular attention to culvert length, environmental conditions created by culverts that may have adverse or beneficial effects on some fish species, and a discussion about evaluating fish passage in culverts from a population viability perspective.