Under Work Package 4 of the NewTechAqua project, experiments are well underway. The potential of using large tanks to allow Greater Amberjack – spawned in sea cages during the year – to undergo maturation and spontaneous spawning, without use of exogenous hormones, was explored. The experiments began on the 9th of June 2020 at the facilities of Argosaronikos Fishfarms, with the supervision of the Hellenic Centre of Marine Research. The goal of this study is to pave the way for organic production of greater amberjack, and reducing the reliance of the industry on frequent handling and hormonal treatments of these large breeders.
Fish reared in a sea cage were selected based on their reproductive stage -after obtaining a gonadal biopsy- and were grouped in two broodstocks placed in separate 70 m3 tanks. One broodstock was treated with the established hormonal treatment using controlled release GnRHa implants, which has been shown in previous studies to induce spawning. The other broodstock was left untreated.
As expected, the GnRHa-treated broodstock started spawning the following day, as in the previous years with the already established and published protocol. Untreated fish also begun spawning and they have so far produced 2 spontaneous spawns with about 2.5 million eggs each, with very high fertilization rates (>75%). . The results confirm the experimental hypothesis, that Greater Amberjack reared in sea cages during the year and placed in large tanks during the spawning season, do not need to be treated with exogenous hormones to undergo maturation and spawning. The experiment will be concluded in early July.
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