Sound is one of the most important sensory stimuli underwater due to the far distances and speed that it is able to travel at. It has been previously shown that anthropogenic sounds in the ocean can affect foraging as well as other behaviors. Scientists have been using Acoustic Deterrent Devices (ADD) in order to deter possible predators from aquaculture facilities. The auditory structure in sharks is arranged with paired inner ears that can detect the particle motion component of sound. Furthermore, cartilaginous fishes do not have a swim bladder which enables them to have a reaction to the pressure changes created by sound and it has thus been thought that they are only sensitive to the particle motion. The sacculus and macula neglecta are the parts of the body that have been shown to have responsiveness to particle motion in these fishes and are also sensitive to low frequency sounds, such as waves or bubbles, and could reach up to 1.5 kHz and, depending on the species, 200-600 Hz. When an atypical sound is high frequency, loud or abrupt, or chaotic/arrhythmic, it could cause the shark to have an aversive or more investigative behavior. 

It has been previously shown that orcas (Orcinus orca) prey on cartilaginous fishes, including rays and sharks. Orcas are highly vocal animals that can produce complex and specific calls along with echolocation clicks and whistles. Some of the orca calls possess a high-frequency component (HFC); but the calls always have a low-frequency component (LFC). The LFC has different temporal sequences that are separated by shifts of the pulse repetition rate and are able to have frequencies lower than 3 kHz which thus overlap with the previously described shark hearing range. 

In an experiment conducted by Chapuis L. et.al. it was found that in both types of sharks studied (reef and coastal sharks along with white sharks) there was a significant difference in the time spent in close proximity to the source of the acoustic stimulus while the orca sound was being played in contrast to the control trials. Using a baited underwater camera rig, the scientists were able to record the behavioral responses of eight species of sharks (seven reef and coastal sharks, and white sharks). The studying of the reef and coastal sharks took place at three field sights in Exmouth, Western Australia specifically at VLF Bay, Burrows Reef, and North West of the Marion Islands. The reef and coastal sharks were unable to be individually identified.The study of the white sharks took place in Mossel Bay, South Africa at two field sites over twelve days at Seal Island and Hartenbos river mouth. The white sharks were able to be identified by individualized markings, scars etc. The scientists predicted that there “would be an ‘orienting’ response (either toward or away) instead of a startle and/or defense reaction, which could be expected following a sudden presentation of a novel sensory stimulus” (Chapuis, L. 2019) It was found that it took the white sharks a longer time to present themselves on the screen and also spent less time on screen while the artificial sound was played. The reef and coastal sharks showed specifically that they respond differently to both of the sound stimuli when compared to the control. The white sharks showed no behavioral difference to the orca calls that were recorded off the coast of South Australia; they might show sensitivity to orca calls from a different region but that has yet to be confirmed. The reef and coastal sharks displayed interspecies differences within the behaviors displayed. The ‘species’ factor was a very good predictor of the time spent within the area, the time the sharks arrived along with the total behavioral resources. Findings from this study suggest that species have different responses to auditory stimuli and that the behavioral reactions to auditory stimuli can vary within individuals. The intraspecies differences could possibly stem from differences in sex, age, size, and group dynamics/social hierarchy but there is still so much more to be understood about the behavioral aspects of cartilaginous fishes. In the future, it may be possible to develop long-term, static management strategies to use in shark mitigation and it would be even more likely if this would be able to be combined with a multimodal system. 

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