Common carp (Cyprinus carpio L.) are hearing specialists and can detect the pressure component of sounds over a broad frequency range (up to several KHz) and at low sound intensities. Experimentally, the application of underwater acoustical equipment to reproduce ‘fish’ sounds has been tested on cyprinids to elicit trained responses, restrict movements and most notably, to attract and concentrate dispersed populations. Regarding the latter, carp feeding sounds were successfully used to lure carp to specific locales within baited and unbaited lakes. This behavioural response was often immediate and resulted in large aggregations of carp at the sound projector. Further, carp are positively rheotactic and will actively seek the source of flowing water. While there are several potential sensory triggers for this movement (i.e. flow, entrained scent, sound), sound can travel vast distances underwater and is therefore a key sensory component that is likely to initiate exploration for the source of flow, particularly in fish at larger distances from the source that may not yet “feel” or “smell” the flow.
Notwithstanding, an attractive sound can be a repulsive sound if not played back at natural levels. While this requires careful experimentation in order to capture and replay attractive sounds at appropriate sound pressure levels (SPL) it also opens up the possibility of using acoustic repellents to dissuade fish from entering spawning grounds or to help herd fish to areas where they can be captured easily. Thus, when used in conjunction with current integrated pest management technology, acoustics may increase carp harvesting success; particularly in lentic systems (i.e. wetlands) where traditional olfactory cues (pheromones, amino acids) that rely on dispersal by flow are not effective.
The specific objectives of this study were to determine the utility of underwater sounds for attracting and repelling carp for management purposes. Two attractant sounds (carp feeding and flowing water) and one repellent sound (high, low/mid and very low frequencies coupled with explosion sounds) were tested over a series of 28 experiments at three different locations within an experimental lake. A VEMCO VPS array was used to monitor the response of eight acoustic tagged carp. This system provided positional data of each tagged carp approximately every 90 seconds. As a measure of attraction or repellence, Eonfusion 2.2 geospatial software was used to determine the time each tagged carp spent within four distances from the playback system (5 m, 10 m, 25 m and 50 m) both before and during each experimental period.
Although the frequency range and calculated sound pressure levels (SPL) confirmed that all experimental sounds were played at biologically relevant levels, the results indicate that feeding and flowing water sounds have a limited effect and therefore do not appear suitable for aggregating carp for harvesting purposes. As previous successful attraction experiments on carp were conducted in clear lakes, it is hypothesised that the reported attraction could be partly attributed to the visual stimuli provided by the researchers standing at the lakes edge or sitting within a boat during the experiments. There were no visual stimuli offered during the current experiments as they were conducted in a turbid lake and care was taken to stand away from the lakes edge during experimental periods.
Interestingly, the “assumed repellent” sound seemed to act as an attractant. Even though tagged carp were aggregated near the speakers by broadcast feeding prior to the repellent experiments there were distinct behavioural differences between feeding and experimental times. During feeding, carp displayed exploratory movements while during the experimental period all tagged carp formed a tight aggregation directly at the speaker. This indicates that the repellent sound or a component of the sound (i.e. mid/high frequencies) may be a useful attractant and this warrants further research.
Download the full report by clicking on the cover image above right or the link below.
|Author||Thwaites LA and Fredberg JF|
|Publisher||Invasive Animals CRC|
|Institution||South Australian Research and Development Institute (Aquatic Sciences)|
|ISBN/ISSN||Web ISBN: 978-1-921777-69-1|
Carp Acoustic Attractants and Repellents [3Mb PDF ]
PestSmart toolkit: Carp - www.pestsmart.org.au/pest-animal-species/european-carp/