Synchronization of common carp (Cyprinus carpio) feeding aggregations through acoustic conditioning in a natural lake setting

Common carp (Cyprinus carpio) is one of the world's most widely distributed invasive fishes.Their high abundance and destructive feeding habits often lead to eutrophication, high water turbidity, and decimation of aquatic macrophytes.A relatively new control method for carp uses pop-up net systems ("box nets") and bait placed within the net.Carp can quickly learn the bait location, which is often carp-specific, and form feeding aggregations, allowing large numbers of carp to be removed without significantly impacting native fish.However, the efficacy of box nets depends on the size and synchronization of carp feeding aggregations.Here, we investigated if acoustic conditioning might be used to enhance bait-induced carp feeding aggregations in a lake.Two study sites were established in Harrisons Bay, Lake Minnetonka, Minnesota, USA, in which 142 carp were tagged with passive integrated transponder (PIT) tags.Each site was subjected to sound-plus-bait, baitonly, sound-only, and no-stimuli treatments over the summer while the presence of carp visiting each site was continuously monitored using PIT antennas.While the carp did not respond significantly to the acoustic cue alone, pairing it with bait seemed to contribute to more synchronized feeding aggregations, resulting in faster and greater recruitment of carp to the sites after bait was dispensed.Specifically, the sound-plus-bait treatment was expected to recruit, on average, 11% more carp than the bait-only treatment.Further, the time to recruit 90% of the nightly tags decreased by 28% when bait was administered with the acoustic cue vs. alone.These findings suggest that adding an acoustic cue to bait applications might enhance the efficiency of bait-and-removal strategies and accelerate control of common carp populations.