Determining and testing the optimal pure-tone frequency for use in acoustic conditioning of free-ranging common carp (Cyprinus carpio)

Abstract

Pure-tone frequencies of 400, 700, and 1000 Hz were tested to determine which achieved the strongest response when used in conditioning experiments on captive common carp (Cyprinus carpio) for the purpose of determining the most effective frequency to use in conditioning experiments on free-ranging common carp. Captive common carp were shown to have the strongest response to the 400 Hz frequency after training that associated sound with food. Response was quantified as moving into a feeding arena when the sound was broadcast, and all frequencies achieved conditioning within five days. Secondly, the attenuation of the three frequencies were compared in a Waikato lake (Lake Kaituna) containing common carp. The ability to maintain signal strength over distance is necessary for frequencies used in the acoustic conditioning of free-ranging common carp due to the potentially large distances involved. Attenuation of the 400 Hz and 700 Hz pure tone frequencies were not significantly different but were both lower than that of the 1000 Hz frequency. The 400 Hz pure tone frequency was used in subsequent experiments on the acoustic conditioning of free-ranging common carp in Lake Kaituna because of superior performance in acoustic conditioning of captive common carp and low attenuation in a natural water body containing free-ranging common carp,. Thirdly, the 400 Hz pure tone was evaluated for its ability to be associated with food by free-ranging common carp. Capture rates at treatment sites where 400 Hz pure tone was broadcast compared to control sites where no sound was broadcast following a five-day training phase and 24 h of no sound or food, were 2.1 times greater during a three-day capture phase. This study demonstrates the trainability of common carp, a trait that can be used to improve control of wild common carp populations.