# Acoustic Characterization for The Feeding Activities of _Haliotis_ _discus_ _Hanmai_
## 2 Materials and Methods  
### Experimental Design  
The Pacific abalones _H. discus hannai_ with shell length of 60 \(\pm\) 2.7 mm were from Fuda Abalone Farm in Jinjiang, Fujian Province, China. All abalones were transported from the farm into the laboratory and then acclimated in the same environment for 3-5 days before the experiments. The experiments were divided into four groups: abalones in Group A were fed with fresh _Gracilaria leananeiformis_ once a day at 6 p.m.; Group B were placed on a small amount of sand as impurities at the bottom of the tank. As the control groups, Group C did not have abalone or food and Group D did not have abalone but _G. leananeiformis_ was added. Throughout the experiments, only one abalone was observed in Groups A and B each time, and each abalone was continuously observed for 5 days. During the experiments, 10 abalones were used in Groups A and B, respectively, and each abalone was only used once. Group A was provided about 5 g of seaweed every day to ensure that the food would not be eaten up, Group B was provided about 10 g of sand for each abalone, and the weight of the food placed in Group D was the same as that in Group A. During the experiments, acoustic signals were recorded using an acoustic recorder (Song Meter SM4 BAT FS Ultrasonic Recorder). Because abalone is a nocturnal benthic animal, an infrared camera (Shenyou 5 megapixel high-definition infrared camera) was used to record abalone's activities in the environment without artificial light. Table 1 shows the detailed information of the devices. \begin{table}
\begin{tabular}{c c c} \hline
**Equipment** & **Parameter Name** & **Parameter Information** \\ \hline \multirow{6}{*}{Song Meter SM4 BAT FS Ultrasonic Recorder} & Channels & 1 \\  & Recording Format & 16-bit PCM WAV \\  & Supported Sample Rates (kHz) & 192, 256, 384, and 500 \\  & Amplifier Gain & 0 or 12 dB \\  & High Pass Filter & Selectable 2-pole at 16 kHz \\  & Anti-alias Filter & 2-pole at 156 kHz \\  & Equivalent Input Noise & in dBVrms (>10 kHz, 0 dB gain) \\ \hline \multirow{2}{*}{Shenyou 5 megapixel high-definition infrared camera} & lens size & 3.6 mm \\  & video format & H.265 \\ \multirow{2}{*}{Shenyou 5 megapixel high-definition infrared camera} & SNR & \(\geq\)48 dB \\  & pixel & 5 million \\ \hline \end{tabular}
\end{table} 
Table 1: The detailed information of the equipment used in the experiments. The abalones were placed in a cylindrical acrylic tank (as shown in Figure 1) filled with fresh seawater. The hydrophone was placed in the center of the tank and connected to an external acoustic recorder. An infrared camera equipped with a filter was placed under the tank to assist the acoustic signal to judge the eating behavior. A layer of sound insulation cotton was wrapped around the data acquisition device to absorb the noise of the surrounding environment, especially the noise from the water circulation device. In order to eliminate the noise as much as possible, we also used sound insulation cotton to wrap the water circulation device and put it as far from the tank as possible. The water circulation device delivers and oxygenates seawater during the experiment, and it was placed at the same height as the data collection device. During the experiments, the water pump was used to pump water from the water circulation device to the data collection device through the water pipe. At the same time, due to the principle of the connector, the water in the data collection device also flowed back through the water pipe. In this way, the water could be circulated and the two separated devices could also effectively reduce the influence of the noise of the water flow on the acoustic data collection. During the experiments, the water temperature was controlled in the range of \(20\pm 1\)\({}^{\circ}\)C, and half the seawater was regularly replaced every day to remain fresh. Aeration was  
Figure 1: The experimental setup and abalone in the abalone acoustic experiments.