Capture of wild juveniles, growth and spawning of the southwestern Atlantic wreckfish (Polyprion americanus) in Argentina

Abstract

Wreckfish (Polyprion americanus) is a marine fish of great interest as a new aquaculture species due to its easy adaptation to farming conditions, rapid growth and market price. In the Southwestern Atlantic Ocean, the species forms a genetic stock different from that of the Northern Hemisphere and also to populations of the South Pacific. This study presents the research conducted in Argentina from 2011 to 2020 on the development of a wreckfish broodstock from juvenile specimens. Wreckfish (n = 21) were caught with fishing rods at depth between 18 and 75 m depth, off the coast of Buenos Aires Province, Argentina (37°30′S - 39°00′S). All fish suffered barotrauma, but specimens captured at a depth < 45 m and whose swim bladders were deflated by puncture had a survival rate > 90%. Juvenile wreckfish (n = 12) with an initial body weight of 2–3 kg were kept in a recirculating aquaculture system (RAS) and fed local fish for 36 months. During this on-growing stage, a natural photoperiod regime with reduced light intensity was accompanied by seasonal variations in the RAS's thermal regime (14–19 °C). From then on, a maturity and reproductive protocol was implemented, where the temperature was lowered (12–17 °C) and the diet was complemented with a formulated semi-moist feed. Juvenile wreckfish grew fast, gaining about 2.5 kg in 11 months with a specific growth rate (SGRBW) of 0.2% day−1 and reaching 10–12 kg in 36 months. There was no significant difference in growth performance between sex groups during the on-growing stage. However, from months 36 to 57, the SGRBW of females (0.058 ± 0.008% day−1) was significantly higher than males (0.035 ± 0.005% day−1). After 67 months in captivity, the first natural spawning was achieved in a communal tank with a sex ratio 4 females: 6 males. Two consecutive spawning seasons were analysed, which showed a large daily variation in total number of eggs, percentage of floating eggs (potentially viable eggs) and spawning intervals. A marked improvement in spawning performance was observed from one season to the next. In the first season, a total production of 5.21 million eggs was reached, of which only about 2.7% were floating, while in the second season the values increased to 13.23 million eggs and 32.6%, respectively. We have successfully developed a broodstock of wreckfish capable of achieving natural spawning. Further research is needed to obtain reliable spawning and large production of high-quality eggs.