# Acoustic Characterization for The Feeding Activities of _Haliotis_ _discus_ _Hanmai_
###### Abstract
Abalone is an economically important cultured mollusk species in the world and has been regarded as the jewel in the seafood crown for thousands of years in China. With continuous overfishing and water pollution in the wild, more and more natural habitats are destroyed and the number of wild abalones has become lower and lower [24]. As a result, abalone farming production has substantially increased in the past two decades. Therefore, there are many related studies focusing on abalone farming, including genetic breeding [25; 26], behavior [27], nutrition and feed [28], physiological ecology [29], etc. However, abalone likes to stay in an environment with relatively dim light, and aquaculture water is always turbid, which makes it difficult to use underwater cameras to observe and study the behaviors of abalone. [PERSON] pointed out that sounds produced by _Haliotis crackerodii_ can be heard during feeding [22]. However, to the best of our knowledge, there are no studies focusing on abalone acoustics. Passive acoustic technology is an acoustic method that can be used to detect the sound of animals in their natural environment [30]. In an underwater environment, a hydrophone can be used to monitor the sound actively produced by the target [31]. By studying the acoustic characteristics of aquatic animals, it is possible to crack the biological significance of those sounds and to identify the species and activity behaviors of the vocalizing animals [1]. In underwater environments, acoustic wave is the optimal choice for propagations in most scenarios [32]. Furthermore, passive acoustics do not require any attachments equipped on the detected objects. To monitor the feeding activities of aquatic animals, most of the research relied on direct observation [33] or video recording [34]. These methods, especially direct observation, are difficult for further analyses of the acoustic characteristics. Meanwhile, with passive acoustics, we can clearly review and analyze the acoustic signal. By comparison, the application of passive acoustics in aquaculture has great potential [35]. Therefore, passive acoustics has been used to monitor the behavior, distribution, and sound characteristics of shrimp, whales, manatees, etc. [30]. [PERSON] et al. [20; 35] realized the analyses of the feeding sound of prawn and measured the feeding consumption through passive acoustics. [PERSON] et al. [36] evaluated the relationship between acoustic signals and diet lengths of _Litopenaeus Vannamei_ through passive acoustics. The research on the acoustic behavior of fishes such as _Micropterus salmonide_[37; 38] and _Scophthalmus maximus_[8]has also been applied to their farming activities. Based on the extensive acoustic research results of fish and crustaceans, passive acoustics has been gradually applied in the actual aquaculture production process, such as shrimp productions reported by [PERSON] et al. [39]. Our research on the acoustic characteristics of abalone is conducive for further biological research on abalone and can help abalone aquaculture practitioners improve their farming strategies to increase the revenues. Therefore, the objective of this work is to study the acoustic activities of abalone using passive acoustic method in order to quantify the acoustic characteristics of abalone feeding activity and to study the pattern of acoustic signal during abalone feeding. The results can serve the abalone farming industry, wherein the acoustic description and measurement can be adopted for optimizing the feeding strategy and improving the farming efficiency of abalone. The rest of the paper is organized as follows: Section 2 describes the experimental setup, method, and software and hardware used to record and process the acoustic signals of abalone. In Section 3, the eating process of abalone is described and the acoustic characteristics of abalone feeding activities are analyzed.