Study on large yellow croaker's pellet feed behavior using acoustic signals

In recent years, China has achieved remarkable achievement in deep-sea aquaculture of large yellow croaker (Larimichthys crocea), not only in terms of production, but also in terms of quality. Nevertheless, feeding operations are affected by natural calamities such as typhoons and powerful ocean currents. Therefore, to further improve the technological development of L. crocea culture in the deep sea, we used the fish with an initial body mass of (122.62±11.08) g and a body length of (17.9±1.04) cm as samples. Then we applied an underwater acoustic measurement system (Bandwidth of 20 Hz−20 kHz) to capture the underwater sound and observe the behavioral responses of the fish. The results indicate that the feeding sound of the fish could be distinctly classified into two types: pure swallowing and swallowing accompanied by chewing. Both swallowing and chewing produce sound mainly within the frequency of 6 Hz−13 kHz. Prior to feeding, the acoustic signals emitted by the fish were relatively sparse. However, when feeding began, the number of acoustic signals increased significantly. In a single feeding cycle, an individual fish exhibited 4−7 feeding behaviors, with pure swallowing being relatively infrequent. Swallowing was usually accompanied by 1−2 pulsed acoustic signals. Single pulses had a shorter duration, while double pulses had a longer one. The duration of these signals ranged from 0.05 to 0.25 sec, and the average sound pressure level generated was approximately (74.51±3.91) dB. When chewing, the fish most commonly produced 5−7 chews, with the chewing intensity gradually decreasing from (73.27±2.62) to (55.82±1.43) dB. Furthermore, as the number of feeding behaviors increased, the foraging duration of the fish also extended significantly, displaying a linear positive correlation.