Tag Archives: Topeka shiner

Darkness in Box Culverts Not a Likely Barrier to Topeka Shiner

Darkness box culverts does not present a complete barrier for southwestern Minnesota fish species, according to a new MnDOT study. The findings will reduce the cost and  delay of future box culvert replacement projects.

“This research will allow MnDOT to save both time and money when replacing other box culverts in southwestern Minnesota by eliminating the need for a fish passage study for each one,” said Scott Morgan, Principal Hydraulics Engineer, MnDOT District 7.

The research project is one of several undertaken by MnDOT and the Local Road Research Board to better understand fish passage (more at mndot.gov/research), and ultimately develop a Minnesota culvert design manual for accommodating aquatic species.

What Was Our Goal?

In this study, researchers developed several objectives in their efforts to assess the effect of low light levels on fish passage through replacement box culverts. As part of this effort, they wanted to determine typical light levels in the replacement culvert and other box culverts in the region. They also sought to determine if the Topeka shiner and other fish move through culverts in the same numbers they pass through control areas in the same stream, and whether light levels affect frequency of movement. Finally, if a barrier is determined, researchers sought to design or recommend a method for mitigating light in the culvert.

What Did We Do?

In the field, researchers characterized light in long box culverts (at least 8 feet by 8 feet) by collecting many light levels with a light meter at the water surface within the three culverts and at control reaches. They also measured light levels within the water column to characterize the light conditions a fish would experience.

To determine whether Topeka shiners passed through culverts in similar numbers as through control reaches of the same stream, and whether light levels affected their passage, researchers employed a mark-and-recapture process. They caught fish upstream and downstream from the culverts or control reaches, marked them with an identifier indicating where they were caught and released, and then resampled to see where fish moved. They also noted other culvert features that could affect passage, such as water depth and velocity.

Image of fish tank.
In light manipulation experiments at the St. Anthony Falls Laboratory, Topeka shiners and fathead minnows were allowed to choose channels to swim along. The degree of shade in one channel was adjusted from light to deep shade.

To control for confounding variables that could affect fish movement, a laboratory study measured Topeka shiner preference for light or dark channels. Researchers used a 25-foot-long double channel box with water diverted from the Mississippi River. Fish could choose to swim along light or shaded lanes as they preferred in this light manipulation experiment.

What Did We Learn?

Although there has been increasing concern over the potential for culverts to create behavioral barriers for fish and other organisms, this was the first study that quantified these behavioral effects for fish passage. Light levels in large box culverts were not identified as a potential barrier to the fish communities present in southwestern Minnesota. Two out of the three culverts monitored showed reduced fish passage compared to the control reaches; however, fish—including Topeka shiners—were able to pass through all three.

The longest and darkest culvert had the greatest difference in movement between the culvert and the control, but this variation could not be attributed solely to light levels. This finding was supported by experiments at the St. Anthony Falls Laboratory, where fish that could select either a shaded or lighted channel showed no avoidance of the shaded channel regardless of the shading level.

The light measurements in three culverts yielded an extensive data set that can be used to model light levels through culvert barrels. Light levels at the water surface depended on the culvert entrance, dimensions, construction material, orientation and elbows, while light levels in the water column were also affected by turbidity.

What’s Next?

The conclusions of this study apply only to Topeka shiners and other small warm water fish species, and to large box culverts like those studied. Additional research is required to investigate possible barriers created by smaller, darker culverts to light-sensitive fish species and the interactions between light and other variables such as velocity.

This post pertains to Report 2017-44, “Culvert Length and Interior Lighting Impacts to Topeka Shiner Passage,” published November 2017. The full report can be accessed at mndot.gov/research/reports/2017/201744.pdf.

Culvert research aims to protect endangered small fish

The Topeka shiner
The Topeka shiner, a small minnow that inhabits slow-moving prairie streams, was once widespread and abundant in portions of Iowa, Kansas, Minnesota, Missouri, Nebraska and South Dakota. It now inhabits less than 10 percent of its original geographic range.
(Photo courtesy of the Minnesota Department of Natural Resources)

In a new study funded by the Minnesota Department of Transportation, engineers are trying to ensure that new culverts do not degrade the habitat of an endangered fish in southern Minnesota.

The state has already researched how to better accommodate fish passage at river and stream crossings. Now it is looking at design guidelines for culverts that specifically impact the Topeka shiner, a small endangered fish found in five Midwestern states.

In Minnesota, the Topeka shiner is known to live in at least 57 streams, totaling 605 miles, within the Big Sioux and Rock River watersheds.

“The Topeka shiner is reported to have been erased from about 50 percent of its historic range in Iowa and much of its range in Minnesota, which is why Minnesota is so intent on doing what it can to help this fish thrive here,” said Alan Rindels, MnDOT’s project coordinator for the research.

The Topeka shiner is endangered due to the degradation of stream habitat, stream channelization, non-native predatory fishes and construction within waterways.

Culverts might impede the passage of this small minnow for a number of reasons, including that they might be too long, lack sufficient depth or carry water too fast.

Culverts allow water to pass under roads.
Culverts (also called small bridges) allow water to pass under roads. Occasionally, they can harm a stream’s fish habitat by inadvertently acting as a barrier to fish passage or migration. On the West Coast, large-scale efforts are under way to protect migratory salmon, and in Minnesota, culvert designers are concerned about fresh water species.

In addition, long culverts block sunlight, which possibly discourages fish from swimming through. Typically, older culverts are replaced with longer culverts to improve road safety and minimize maintenance costs. To eliminate or minimize impacts to the Topeka shiner, the state is trying to determine if light mitigation strategies are necessary.

Researchers from the University of Minnesota’s St. Anthony Falls Research Laboratory will monitor a newly installed culvert (110 feet in length) and a few other culverts in critical Topeka shiner habitat streams during spawning and fall movement.

Additionally, a laboratory-based light manipulation experiment will examine the behavior of the warm-water fish when presented with a dark culvert.

Guidelines for culvert design in Topeka shiner habitat will be developed based on these results, as well as examples from neighboring states. The state is also collaborating with the U.S. Fish and Wildlife Service and affected Minnesota counties.