How Did the Fish Get Across the Road?

Southern redbelly dace. Photos courtesy of CATT.

Early in the morning, a crew is gearing up for another day. Dip nets, waders, buckets, snorkeling gear and measuring devices are loaded into the truck. Off they go on another assignment—another stream to survey, monitoring equipment to install, aquatic organisms to inventory, stream crossings to photograph.  After a long drive back to the office, the crew downloads data, creates GIS maps, and prepares reports and restoration plans to give to resource managers. 

The crew is part of the Center for Aquatic Technology Transfer (CATT) located in Blacksburg, Virginia, a group of U.S. Forest Service Southern Research Station (SRS) scientists and technicians working mostly on National Forest Service System land. This science delivery program focuses primarily on aquatic related management challenges.

Challenges exist for many organisms where a stream intersects with a road crossing. 

A damaged stream crossing in need of repair, a difficult passage for fish and other aquatic organisms. Photo courtesy of CATT.

“Stream crossings are part of the larger issue of habitat connectivity,” says Craig Roghair, fisheries biologist with the SRS Forest Watershed Science unit.  “All aquatic organisms require connected habitats to persist, though the amount of habitat required and time it must be connected can vary widely depending on the species. Once connection to a particular stream reach is reduced or lost, whether from a dam or an impassable culvert, it is only a matter of time until species will be lost from that part of the stream.”

In the eastern United States, there are more than 50,000 places where roads cross streams on lands managed by the National Forest System. Each of these crossings represents a potential impediment or barrier to the movement of over 600 native freshwater fish species. The Forest Service recognizes the importance of modifying or removing those crossings identified as barriers to meet its objective of restoring and maintaining native species diversity, according to a report prepared by CATT in 2007.

Crossings can consist of a variety of structures which range from natural fords (driving through a stream), concrete fords, vented fords, culverts made of all types of materials, concrete boxes, pipe arches and open-bottom arches—to dams and bridges.  Fords and culverts are the most common crossing types on National Forest System managed lands and can present a variety of problems in terms of aquatic species crossing. 

A repaired crossing, now an easy passage for aquatic organisms. Photo courtesy of CATT.

CATT is giving aquatic organisms a better chance at moving freely along waterways by working with internal and external partners to deliver science-based ways to improve aquatic organism passage at road-stream crossings.

“We’ve focused  primarily on non-game fish species such as minnows and darters. Since fish are restricted to the wet area of the stream, they present a worst-case scenario for aquatic organism passage studies. Other stream inhabitants such as insects or crayfish have life stages that can fly or crawl over crossings,” says Roghair.

Since 1995, CATT has partnered with National Forests in 13 states and Puerto Rico, providing managers with tools and information from data collected on the forests. Recent examples of CATTs work on national forests include projects on the Chattahoochee-Oconee National Forest in Georgia, where 99 road-stream crossing sites were visited—35 of those inventoried—and work on the Mark Twain National Forests in Missouri, where 1784 crossings were assessed.  

The results provide managers with tools and information to prioritize money and resources to improve streams and provide ways for aquatic organisms to cross the road.

Read more about CATT projects, reports and results. 

For more Information, email Craig Roghair at

Access the latest publications by SRS scientists.

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