Size matters: Variability in the acoustic parameters during feeding activity of Penaeus vannamei in different size classes

Abstract

Penaeid shrimp emit click sounds during feeding activity generated by the collision of mandibles. These sounds have been used as a basis for research of feeding behavior and acoustic-based automatic feeders in shrimp farming. However, the use of automatic feeders is generally recommended for shrimp larger than 2 g or more. The aim of the present study was to evaluate the click acoustic parameters during feeding activity of Penaeus vannamei from post-larvae up to 12 g in laboratory. Twelve progressive weight classes (0.01 to 12 g) along nursery and grow-out phases were recorded in tanks internally covered with an acoustic foam. Recordings were carried out using an omnidirectional SoundTrap 300 STD hydrophone (sampling rate: 288 kHz; 16 bits). At the end of the recordings, shrimp were measured (body weight and cephalothorax length) and had their mandibles dissected for length measurements. The clicks emitted by shrimp during acoustic recordings were automatically detect using Raven® software, and 100 clicks per weight class were randomly selected for acoustic sound characterization (low, high and peak frequency, maximum power and duration time). The clicks start to be emitted by P. vannamei at the average weight of 0.01 g, with a band frequency between 15.4 and 70.5 kHz and low maximum power (23.2 dB). The low and peak frequency showed an abrupt decrease until shrimp reached 1.16 g, while maximum power and high frequency presented an opposite pattern. The click sound duration time did not show a clear variation among the different weight classes evaluated. Acoustic parameters showed a significant linear relationship with mandible length, indicating a direct influence of this structure on sound emission. The regression derivative analysis estimated that click maximum power stabilized from 1.48 g onwards, while low, high and peak frequency stabilized from 3.08 g shrimp onwards. The results suggest that it would be possible to anticipate and optimize the use of acoustic-based automatic feeders in P. vannamei farming.