For three consecutive years, the European Percid Fish Culture (EPFC) organized in collaboration with Inagro an international hands-on workshop on the out-of-season reproduction of pikeperch (Sander lucioperca). This year, the fourth edition of this workshop was suspended because of Covid-19.
This mandatory break was the best opportunity for Inagro staff to put in practice by themselves the knowledge acquired in the previous years. The broodstock maturation protocols, the techniques to evaluate the quality and stage of gamete, and the fertilization procedures taught by Daniel Żarski (IARFR, PAS, Olsztyn, Polan) and Uroš Ljubobratović (NAIK HAKI, Hungary) during the previous workshops were applied. As a result, more than 3 liters of good quality eggs were fertilized. An amount of these eggs was sent to colleagues in Germany for research.
Broodstock maturation protocol
The maturation protocol lasted 12 months and was carried out in a climate control room equipped with a recirculating aquaculture system (RAS), connected to two tanks, where females and males were stocked separately. Pikeperch broodstock followed a photo-thermal regime where water temperature, light intensity and photoperiod were continuously monitored and controlled to stimulate appropriate gonadal development. Our protocol is divided in four phases:
- Resting phase: Allows the broodstock to recover from the previous breeding season, and at the same time prepares the fish for a new reproduction cycle. During this period, water temperature is kept at 23 °C.
- Cooling phase: The temperature of the water is gradually reduced to 8 ⁰C to stimulate oocyte growth. The photoperiod and the light intensity also decrease to simulate seasonal changes.
- Winter phase: Used to promote the maturation of the oocyte. Short day length (i.e. 8 hours) and low temperature (i.e. 4 °C) are used in this phase.
- Warming phase: The water temperate is increased to 12 °C to stimulate the final maturation process.
During the whole process, with some exception, the broodstock was fed with a mixture of different commercial diets (i.e. broodstock and growout feed) to provide the necessary nutritional requirements, especially fatty acids, to produce high quality eggs and larvae.
Controlled reproduction and egg quality assessment
In the controlled reproduction of pikeperch, hormonal treatment is applied to synchronized ovulation. Injections are applied at the end of the maturation protocol, just after the winter period, when females are entering to the final oocyte maturation (FOM) stage.
After injection, the females were periodical checked for ovulation. When ovulated they are ready to spawn or in our case to be stripped. The first control on readiness to strip was 72 hours after injection, afterwards we checked all the females every four hours.
Fertilization in vitro
Females and males were stripped manually and the eggs and semen where mixed in a bowl. After a specific protocol aiming are removal of their adhesiveness they were incubated in McDonald jars.
Hatching of larvae
After six days of eggs incubation, at 16 ⁰C water temperature, around 2 million larvae hatched, this was a 35% increase in hatching rate compared to the last year. At day 4 after hatching, a significant number of them were sold true the EPFC network. At the moment, Inagro has more than 300,000 larvae in its hatchery system. An amount of these larvae will be sold once they reach the juvenile phase (5-10 g), the rest will be used as a stock for the grow-out phase in 2021. These adults will go to the fish market or become broodstock animals.
Do you want to know more details about all the steps involved in the artificial reproduction of pikeperch? In september 2021, the 4th workshop in reproduction of pikeperch out-of-season will be organised by the EPFC, hosted by Inagro and supported by the experts Daniel Żarski (IARFR, PAS, Olsztyn, Polan) and Uroš Ljubobratović (NAIK HAKI, Hungary). During this workshop, participants will learn the key concepts of pikeperch reproduction and out-of-season development processes in controlled conditions. Afterwards, they will have the opportunity to apply the theoretical learned knowledge in the practical center for aquaculture at Inagro.
Image: control of pikeperch females
Image: fertilized pikeperch eggs in McDonald jars
For more information, contact Stefan Teerlinck: firstname.lastname@example.org