Responses of Fish Assemblages to Dam Removal on the Chattahoochee River, Alabama-Georgia

Two mainstem dams on the Chattahoochee River, Alabama-Georgia, USA, were breached in 2012 and 2013 to restore an approximately 3.7-km reach to an unimpounded condition.  Fish were sampled in summer and fall 2014 using electrofishing from three areas within the restored area, as well as from the small reservoir immediately above the upstream dam, which served as a reference area.  A total of 3,069 fish was collected in summer and 1,906 in fall, representing 32 and 30 species, respectively.  Number of species collected declined progressively from the most-downstream to the most-upstream sites below the remaining dam.  More species were collected above the dam than in the two areas within the removal area, but the highest species diversity was below the dam removal area, despite also being effectively the headwaters of the large mainstem reservoir downstream.  Overall, the fish community appears to be characterized by relatively low species diversity and composed mainly of reservoir or river-reservoir fishes.  True recovery of the fish community to pre-impoundment conditions is likely to be a long process, and may need to involve active management actions such as stocking or transporting fish into the restored reaches.