# Acoustic Characterization for The Feeding Activities of _Haliotis_ _discus_ _Hanmai_
###### Abstract  
In order to analyze the sound production mechanism and the acoustic characteristics of _Haliotis_ _discus_ _Hanmai_ during feeding, this paper proposes a multi-source information fusion approach combining passive acoustics with videos. In the experiments, abalones with a shell length of 60 \(\pm\) 2.7 mm were divided into two groups: Group A was fed with fresh macro algae _Gracilaria_ _lemaieformis_ as food once each day; Group B was placed on a small amount of sand as impurities at the bottom of the tank. As control groups, Group C did not have abalone or food and Group D did not have abalones but food was added. The eating acoustic signals of abalone were mainly concentrated in the frequency range between 9.49 kHz and 44.36 kHz, wherein the peak frequency is 37.86 \(\pm\) 2.55 kHz, with the maximum energy \(-\)66.43 \(\pm\) 5.17 dBm/Hz. Each pulse sequence is with a duration of 119.12 \(\pm\) 70.51 ms and consists of several sub-pulses. Nearly 70% of the pulse sequences consist of 1-2 sub-pulses and the duration of the pulse containing one sub-pulse is 42.62 \(\pm\) 19.72 ms. The eating rate was kept at 0.61 \(\pm\) 0.04 times/min at the beginning and was decreased significantly to 0.48 \(\pm\) 0.08 times/min after 60 min. Note that the characteristic analysis of abalone acoustic signals during feeding are first reported in this manuscript to the best of our knowledge, and this paper also demonstrates that the sound of abalone is produced by scraping and grinding food with radula. Because the eating rate decreases with the reduction in the abalone's level of hunger, the results may be used as an acoustic indicator of feeding strategy for the abalone aquaculture industry. p 2023 13 559 2023 10 April 2023 28 April 2023 29 April 2023 29 April 2023 29 April 2023 29 April 2023 29 April 2023 29 April 2023 29 April 2023 29 April 2023 29 April 2023 29 May 2  
their differences under various feeding patterns. The acoustic pressure of _Scophthalmus maximus_ changes significantly during feeding, which can be used in controlling the feeding intensity [8]. [PERSON] et al. [9] tracked ecological acoustics on coral reefs and other marine habitats, which could be used to infer breeding, feeding, and ecosystems' condition. Marine invertebrates have very limited sound production abilities compared with fishes, so there are few related studies, among which shrimp is the most extensively studied. These include bumping, rubbing, carapace vibration, stick-slip friction, biting, bubbling, and contracting muscles [10; 11; 12; 13; 14; 15; 16; 17]. There are different sound mechanisms for different behaviors: when the snapping shrimp encounters danger, it will quickly close its frontal chela and make a harsh sound to deter intruders [18]. Some lobsters can make stridulation through the friction of two parts of their bodies to deter predators [19]. Based on the relationship between the hunger level and the activity behavior, researchers can indirectly judge the appetite of _Penaeus monodon_ by detecting the frequency of the acoustic signal during the feeding activity. Therefore, the feeding can be controlled [20]. Mollusks have a lower frequency and smaller range of activity and less sound signals compared with fishes and crustaceans. There are several reasons for this phenomenon; first of all, shellfish do not have the agility and aggressiveness as animals that need to use sound to deter, evade, or attack predators. Secondly, because some gastropoda feed on algae that are at the bottom of the food chain, they do not need to locate their prey by acoustics [1]. In addition, making sound also tends to attract predators [21]. Therefore, there are currently few studies on shellfish, with most research focusing on the sounds produced during eating. [PERSON] [22] documented the sounds when different species of mollusks rasp different algae or scrape rock. [PERSON] and [PERSON] [23] used passive acoustic to track the spatial requirement and broad movement of spider conch.