Seabird Diversity and Deterrence on Floating Oyster Cages

Abstract

Off-bottom oyster aquaculture involves the use of floating gear, which increases the surface area at the farm and provides roosting sites for seabirds. State authorities require oyster growers to have operational plans that outline mitigation or deterrent strategies to prevent interactions between birds and floating aquaculture gear. However, the effectiveness of deterrents varies based on bird species, and few studies have investigated the impacts of deterrents on seabirds. The purpose of this study was to describe seabird communities at an off-bottom oyster research farm and test the efficiency of a simple, inexpensive bird deterrent. Over 9 months, cameras captured 20,797 bird interactions with floating cages. The primary species or groups roosting on gear included brown pelicans (Pelecanus occidentalis), terns (multiple species), and double-crested cormorants (Nannopterum auritum), with interactions occurring most frequently during September and October. A simple bird deterrent made from plastic lattice and zip ties effectively reduced interactions by 85%. However, deterrent efficiency declined when large groups of brown pelicans were present. In conclusion, the use of a simple, physical bird deterrent on floating oyster cages significantly reduced the number of roosting seabirds while providing an example of an inexpensive and easily replicable design.