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How dams affect crayfish

Crayfishes play an important role in stream ecosystems. However, many species are threatened or endangered. Dams are among the threats to crayfishes, and a new study shows that large dams may harm hundreds of crayfish species over thousands of stream miles.

A side view of a floating crayfish.
Courtesy photo by Guenter Schuster, Eastern Kentucky University (Emeritus Scientist).

Dams are one of many threats to crayfishes. For crayfish, major life events – spawning, survival, and growth – are synchronized with a stream’s historic patterns of flow. Dams change these streamflow patterns, disturb habitat, and impede migration.

A team of researchers assessed the effects of large dams on crayfish assemblages in southern Appalachian Mountain streams. The results show that large dams harm crayfishes and may affect hundreds of crayfish species in thousands of stream miles, possibly altering stream systems by interfering with the numerous ecosystem functions influenced by crayfishes.

The researchers compared crayfish assemblages in similar streams, some with dams and others without. In all the dammed streams, crayfish diversity was lower – both upstream and downstream of the dam. In the un-dammed streams, crayfish diversity was higher farther downstream. Finer-scale assessments did show that, in dammed streams, crayfish density and richness eventually increased farther downstream, which suggests that recovery is possible.

The study shows that large dams negatively affect crayfishes and may affect hundreds of crayfish species in thousands of stream miles, possibly altering stream systems by interfering with the numerous ecosystem functions influenced by crayfishes.

Principal Investigators
Zanethia C. Barnett, Research Fisheries Biologist
Susan B. Adams, Team Leader, Research Fisheries Biologist
RWU
4155 - Center for Bottomland Hardwoods Research
Publication
Effects of impoundments on stream crayfish assemblages
External Partners
Western Carolina University
Memphis Zoo
MS Sandhill Crane National Wildlife Refuge
US Army Corps of Engineers
Eastern Kentucky University