The Effects of Culverts and Stream Barriers to Movement and Gene Flow in Stream Fishes: A Landscape Perspective

Focus Area

Wildlife & Ecosystems


Natural Resources






Over 3 years

Research Idea Scope

The southeastern United States is the center of biodiversity for freshwater fishes and mussels in North America.  Many of these species are imperiled and one of the leading causes of imperilment is habitat degradation (Jelks et al. 2008). A large number of imperiled species live in small streams and road and culvert construction constitute major sources of habitat degradation in these systems Warren & Pardew 1998).  In addition, road construction, culverts and other stream barriers may halt movement of fishes resulting in population fragmentation, loss of gene flow or even extinction (Winston et al. 1991; Wheeler et al. 2005; Wofford et al 2005).  Although studies of the effects of culverts and road construction on stream fishes exist (Benton et al 2005; Norman et al. 2009), most are limited to a few streams or one to two seasons of sampling in a single year and few take into account stream landscape features such as geomorphology and the presence of velocity barriers such as submerged timber. In addition, although movement behavior has been studied, there is almost no information on gene flow and population fragmentation which are the primary subjects of concern for conservation. Consequently further study is needed of how culverts and roads affect movement, gene flow and fragmentation of stream fish populations and habitat quality.  

We will evaluate the effects of different culvert/crossing types including but not limited to: pipe culverts, box culverts, slab culverts, and bottomless culverts, on movement and genetic mixing of the dominant stream fishes in a series of small streams in both Piedmont and Appalachian regions of Georgia.  We will chose streams representative of habitats in other southeastern states to increase generality of our findings.  In addition, we will quantify habitat availability in stream sections above and below crossings.  Specifically we will test whether: 1) movement through different culvert types differs from that in comparable sections of intact stream, 2) genetic exchange above and below various culvert types differs from that in a comparable sections of intact stream, 3) specific culvert types produce different changes in stream habitat above and below the barrier, 4) whether movement/genetic exchange is affected by local stream geomorphology, velocity barriers or other landscape factors, and 5) via replication of culvert type, flow and year, whether results are stream-specific, flow specific, or culvert specific.

We will use a stratified design and instrument sections of stream above and below culverts with Passive Integrated Transponder antennae and then we will tag fish with individually recognizable PIT tags.  Tags small enough for use on stream fishes, many of which have a maximum size of less than 150mm, are now made and have been tested in our laboratory.  We will choose sites in both Appalachian and Piedmont regions because these regions contain the majority of imperiled species in the Southeast.  We will locate 2-4 watersheds in each region with and without culverts and instrument 2-5 streams within watersheds for one to two week periods in spring, summer and fall.  We will attempt to replicate culvert types and have at least one control site per culvert type. If possible, we will tag at least 50 individuals of each species but imperiled species will not be tagged.  At the time of tagging and subsequent recapture, specimens will be identified to species, weighed and measured for length and a small fin clip made for genetic analysis.  Specimens for tagging will be collected via electrofishing, seining or snorkeling.  Instrumentation will include bidirectional antennae located directly below and above the culvert with two bidirectional antennae located further downstream and two more upstream.  Records of fish movements will be recorded on data loggers and checked daily.  Because of the nature of the equipment, personnel will be stationed at each field site during sampling. Habitat analysis ranging from the microhabitat to the landscape level will be conducted during movement sampling events, using the random sampling technique of Grossman & Ratajczak 1998 and GIS with available coverages. At the end of the sampling year (end of autumn) we will electrofish 500 – 750m above and below each sampling site to recapture tagged individuals and record annual growth in mass or length.  Genetic analysis will be conducted as per Scott, Cashner Grossman & Wares 2009.  Whenever possible, we will identify surrogates for imperiled species and devote special attention to these species. We will conduct tagging and genetic studies for two – three years.


Grossman, G. D., and R. E. Ratajczak. 1998. Long-term patterns of microhabitat use by fishes in a southern Appalachian stream (1983-1992): effects of hydrologic period, season, and fish length. Ecol. Freshwat. Fish 7: 108-131.

Jelks H.L.W., Stephen J.. Burkhead N. M. Contreras-Balderas S., Diaz-Pardo E., Hendrickson D.A., Lyons J., Mandrak,N.E., McCormick F. Nelson J. S., Plantania S.P., Porter B. A., Renaud C. B., Schmitter-Soto J. J., Taylor E., Warren M.L. Jr. (2008) Conservation status of imperiled North American freshwater and diadromous fishes. Fisheries, 33,372-407.

Norman, J.R., Hagler, M.M., Freeman, M.C. & Freeman, B.J. (2009) Application of a Multistate Model to Estimate Culvert Effects on Movement of Small Fishes. Transactions of the American Fisheries Society, 138, 826-838.

Scott, C.H., Cashner, M., Grossman, G.D., & J.P. Wares. 2009. An awkward introduction: phylogeography of Notropis lutipinnis in its ‘native’ range and the Little Tennessee River.  Ecol. Freshwat. Fish: 18- 538-547.

Warren, M.L. & Pardew, M.G. (1998) Road crossings as barriers to small-stream fish movement. Transactions of the American Fisheries Society, 127, 637-644.

Wofford, J., Gresswell, R.E & Banks, M.A. 2005. Influence of barriers to movement on within-watershed genetic variation of coastal cutthroat trout. Ecol. Appl. 15: 6628-637.

Wheeler, A.P., P.L. Angermeier, and A.E. Rosenberger. 2005. Impacts of new highways and subsequent landscape urbanization on stream habitat and biota. Reviews in Fisheries Science 13:141-164.

Urgency and Payoff

The southeastern United States faces two factors that render information on the effects of culverts and other stream barrier of high importance: 1) increasing urbanization with concomitant increases in road construction, and 2) climate change. The southeastern United States is the center of biodiversity for stream fishes in the nation, yet many species have restricted home ranges that render then highly subject to disturbance by stream barriers.  The fact that many species have restricted distributions coupled with increased road construction and an increasingly variable climate, make information on how stream barriers such as culverts affect movements and gene flow within these populations of utmost importance.  The resulting information will enable managers to determine the appropriate culvert type for new construction, that is, the culvert type that will minimize the effects of fragmentation and reduced gene flow on stream fishes.  In addition, it will aid managers in identifying existing “problem” culverts and determining if remediation efforts are necessary.  Finally, these data will aid in identifying landscape level habitat factors that either facilitate or inhibit movement and gene flow by stream fishes through culverts or other stream barriers.

Suggested By

Gary D. Grossman & Brian Irwin, University of Georgia & US Geological Survey, 706-255-9082

[email protected]