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Man-made barriers have resulted in a decline in migratory fish species populations by reducing the geographical range of migration, limiting access to necessary habitat including spawning grounds and nursery rearing areas, impacting species life cycles and ecosystems, ultimately resulting in an overall decrease in species biodiversity. Fishways generally allow fish to maintain, extend, or even re-establish migrations over both man-made and natural barriers. Fishways, used in both upstream and downstream lotic environments, are generally classified as either technical or nature-like and are designed to provide aquatic ecosystem sustainability and river connectivity worldwide. In the case of upstream technical fishways (i.e., fish ladder), when appropriately designed and situated, fish ladders allow upstream migrating fish to bypass river barriers to reach river segments suitable for growth and reproduction. While a common method of providing passage in many systems, fish ladders can present biological and engineering challenges and limitations. Importantly, there are common misconceptions related to fish ladders as well as uncertainty regarding their appropriateness as the only perceived solution to a fish barrier. This paper explores and presents some of the shortcoming of fish ladders, and more specifically upstream technical fish ladders, and highlights design elements to consider for providing the highest degree of fish passage efficiency.
Published Date: 2021-12-31; Received Date: 2021-12-10