How dams affect crayfish

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.