Proceedings of the Vertebrate Pest Conference

Double-crested cormorants commonly depredate channel catfish at aquaculture facilities in the southeastern U.S., causing significant economic loss. Prior research has demonstrated regional night-roost harassment (i.e., “major pushes”) to be an effective technique to temporarily reduce cormorant use on aquaculture ponds; however, these efforts were extremely labor intensive and changes in impacts were difficult to quantify. We conducted a preliminary study to investigate the efficacy of site-specific, night-roost dispersal (n = 6) using lethal control on cormorant abundance by monitoring the number of birds at randomly selected aquaculture facilities for 3 days prior to and following night-roost dispersals. The effect of dispersal varied greatly by study site. At one site, the mean abundance of cormorants on catfish production ponds decreased following dispersal; however, on the other 5 sites the mean abundance of cormorants did not change on catfish production ponds following night-roost dispersal. We recommend further research to evaluate the effectiveness of night-roost dispersal using lethal control. Furthermore, we offer recommendations for the design of future large-scale studies, which include improvements to reduce large variation.