On 9 May 2022, NewTechAqua partners launched their final experiments on describing the reproductive behaviour of meagre in captivity.
In the facilities of the Hellenic Center of Marine Research (HCMR) in Crete, Greece, sounds produced by meagre (Argyrosomus regius) during their breeding activity are currently regularly recorded and analysed. Meagre, a member of the Sciaenidae family, is also know known as “croaker” or “drummer” as they produce sounds similar to frogs. Meagre is equipped with sonic muscles along their abdominal cavity adjacent to their swim bladder. These muscles are among the fastest vertebrate striated muscles producing low-frequency sounds when contracted. These sounds are used for communication and are related to reproductive activity and spawning.
In 2022, NewTechAqua partners will produce both video and audio recordings of the sounds produced by meagre during courtship and spawning. Post-doc researcher Ioannis Fakriadis and MSc student Christos Siampazis have treated two broodstock consisting of two males and three males each (Fig. 1) with a GnRHa injection known to induce maturation and spawning.
The fish were placed in two tanks of 15 m3 volume (Fig. 2) after evaluation of their ovarian biopsies and sperm samples, and after being marked with individual visual tags (placed on the side of the fishes as observed in Fig.3) to facilitate the identification of each fish in the tank. The experimental tanks include two underwater cameras and hydrophones placed at the bottom connected to the same data recording device. These samples will be processed for histological evaluation and Computer Assisted Sperm Analysis (CASA), respectively.
The video and sound recordings of the two broodstocks (Fig. 3) will be examined to make an ethogram which will be used to describe and compare the behaviors associated with spawning in relation to sound recordings. The produced eggs will be collected and a sample will be genotyped, in order to assess parentage contribution of the males and examine the existence of any hierarchy. At the end, the objective is to use the recordings of the spawning sounds to “encourage” the fish to mature and spawn in captivity without the need of external intervention through the use of hormones.