Culvert Length and Interior Lighting Impacts to Topeka Shiner Passage

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Status:  Complete
Report Date:  11/15/2017


Long culverts can block sunlight, creating a potential behavioral barrier as fish approach a long, dark culvert. Little research was available about low light as a potential barrier to fish passage, particularly with warm water species such as the federally endangered Topeka shiner. As MnDOT replaces older culverts with longer culverts, information was needed to determine when and if light mitigation strategies are necessary, and to design appropriate light mitigation strategies if necessary. Based on a literature review, field monitoring and laboratory experiments, researchers concluded that low light was not a barrier to the movement of Topeka shiners and other small prairie stream fish. Although two out of the three box culverts monitored limited some (but not all) fish passage, no light mitigation for large box culverts (up to 150 feet in length) was recommended for similar fish communities. Culverts that are very long or have very small openings may benefit from additional light, and other aspects of culvert design may affect fish passage.

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