ABSTRACT
One problem that occurs increasingly frequently is the blockage of fish passage at road culverts. Road and highway construction has increased rapidly in most countries, and shows no signs of slowing down. Road design and construction involves the design of bridges and culverts over every stream crossing, and while bridges are preferable for providing fish passage, the development of new types of piping for culverts has encouraged engineers to give preference to culverts rather than bridges. In addition to swimming ability the biologist must be prepared to provide the limits for timing of migration, so that it can be related to culvert design and timing of flood flows. It must be known or deduced what triggers the migration and whether a delay in migration can be imposed without danger to the fish. There are many ways of reducing the velocity at fish migration flows, all of which involve placing baffles within the culvert.
