Article in aquaculture europe VOL. 47 (2) SEP 2022
Fish farm drum orchestra: Is it possible?
Fig. 1: Underwater cameras
Fig. 2: Externally tagged fish
Yes it is! Not because a fish farm can be considered an ideal place for a percussion concert, since we know that the manmade sounds have a negative effect on the behavior and physiology of fish. It is because a batch of fish is in spawning phase and they are drumming! The meagre (Argyrosomus regius) is an emerging species in the EU-aquaculture sector due to its fast growth rate, low FCR, excellent taste and low fat content (http://www.diversifyfish.eu/meagre-argyrosomus-regius.html). It is a member of Sciaenidae family, commonly known as drummers and croakers. The meagre is one of the five known sciaenid fishes in which both sexes possess sonic muscles and can emit sounds by vibrating the swim bladder (Bolgan et al., 2020). It can produce more than 50 beats per second, when the fastest human drummer only 20! In the framework of NewTechAqua project (https:// www.newtechaqua.eu/), we are trying to decipher the reproductive behavior of meagre (Fig. 1). On May 2022, underwater cameras (Fig. 2) and hydrophones were mounted in two tanks of the Fish Reproduction and Physiology Lab (https://fishrepro.weebly.com/) of IMBBC (https://imbbc. hcmr.gr/). Two females and 3 males were marked externally (Fig. 3) and were placed in each tank after spawning induction using Gonadotropin Releasing Hormone agonist (GnRHa), using well-established protocols (Fakriadis et al., 2020; Mylonas et al., 2015). For five consecutive days, video and audio was recorded and egg quantity and quality was evaluated. Egg samples were collected for further parentage analysis. More than 5 million eggs with high fertilization success were spawned in each tank. In each spawn, a frenzy swimming circle was observed by the fish, guided by the spawning female and followed by the males, which were trying to acquire the best possible place to fertilize the released eggs. Knocks and grunts were recorded and are going to be analyzed in order to be matched – if possible- with specific reproductive behaviors.
Fig. 3: Sampling in Aqualabs, IMBBC, HCMR
What is the ultimate goal? But of course, trying to induce spawning without the use of exogenous hormones, just by mimicking their natural reproductive environment using the proper series of sounds! A very ambitious objective, but one that will help farmers manage their meagre broodstocks and produce “organic” eggs.
References
Bolgan, M., Crucianelli, A., Mylonas, C.C., Henry, S., Falguière, J.C., Parmentier, E., 2020. Calling activity and calls’ temporal features inform about fish reproductive condition and spawning in three cultured Sciaenidae species. Aquaculture. 524.a Fakriadis, I., Zanatta, E.M., Fleck, R., Sena Mateo, D.L., Papadaki, M., Mylonas, C.C., 2020. Endocrine regulation of long-term enhancement of spermiation in meagre (Argyrosomus regius) with GnRHa controlled-delivery systems. Gen Comp Endocrinol. 297, 113549. Mylonas, C.C., Fatira, E., Karkut, P., Sigelaki, I., Papadaki, M., Duncan, N., 2015. Reproduction of hatchery-produced meagre Argyrosomus regius in captivity III. Comparison between GnRHa implants and injections on spawning kinetics and egg/larval performance parameters. Aquaculture. 448, 44-53