Sound production in relation with breeding behaviour in meagre (Argyrosomus regius) in aquaculture conditions

INTRODUCTION

Although sound production has been described so far in little more than 1100 fish species, recent studies demonstrate that this communication modality is shared by nearly two-thirds of actinopterygian species. The meagre (Argyrosomus regius) has a wide vocal repertoire and can emit sounds made of a single pulse up to more than 100 pulses. The calling rate and sound temporal features have been suggested as indicative of reproductive events. The aim of this study was to document sound production during spawning activities and to investigate how sounds relate with specific behaviors when fish are reared in aquaculture.

METHODS

Two broodstocks (Group 1 and 2, each with 2 females and 3 males) were used. At the expected spawning period, reproductive stage was evaluated through ovarian biopsies and sperm quality evaluation, and selected fish were injected with GnRHa. Each breeder was tagged externally, and their behavior was monitored using underwater cameras. Two HTI- 96-Min hydrophones were connected to the audio input of the camera. Using Adobe Premiere, audio files were extracted from the videos (May 5th to May 13th, 2022). All audio files were analyzed by audio and visual assessment (Raven Pro 64 1.4). Meagre sounds were manually labelled on the basis of the number of pulses as knocks, short, intermediate and long grunts (total of 243 h of recordings analyzed, 33,351 sounds selected). The occurrences in which a sound could be associated with distinct behaviors (i.e. trailing, darting and male-to-male agonistic behavior) or spawning, were annotated from the video observations. Sounds emitted during these events were measured for fine temporal features (number of pulses, pulse period and sound duration).

RESULTS & DISCUSSION

Fish spawned for three consecutive nights, beginning 2 days after GnRHa administration. The number of sounds produced increased significantly during spawning days, compared to the ones immediately before GnRHa treatment. Long grunts, in particular, were emitted only during spawning days, when knocks were emitted in long, dense series. Knocks were associated with all behaviors considered and were the only sound type associated with same-sex trailing and male-to-male agonistic interactions. Grunts, on the other hand, appeared associated with different-sex trailing during spawning. These results agree with previous studies that identified long grunts as potential indicators of spawning, as well as with studies conducted in the wild, which reported long choruses of knocks. Knocks and long grunts are, therefore, suggested as "carrier of information" during spawning in the meagre.