Introduction
Pikeperch (Sander lucioperca) farming has been studied extensively in last couple of decades, nevertheless, the progress is still slow. One of the main bottlenecks is still the variable outcome of juvenile production (Policar et al., 2019). According to Müller et al. (2017) hybridization with Volga pikeperch (Sander volgensis) may result in an upturn of favorable properties in production, such as straightforward weaning to the dry feed, and more efficient start of first exogenous feeding as well as the reduction of cannibalism which could improve the rearing in all types of production systems of pikeperch. Triploidization as a method to improve production has already found its application in aquaculture. It is now commonly used in salmonid fish species with the main aim to avoid sexual maturation of animals and thus improve meat quality and growth (Janhunen et al. 2019). Likewise, the existence of a third set of chromosomes increases the chance that recombination of genes will avoid population depression (Fraser et al. 2012). Triploidization might reduce the aggressiveness of the fish (Garner et al. 2008) what might be beneficial in pikeperch considering its cannibalistic behavior in young juvenile stage (Ljubobratović et al., 2015; Colchen et al., 2020) The aim of the present study was to evaluate the effects of hybridization and triploidization on pikeperch larviculture.
Material and Methods
The eggs used in the present trials were obtained via artificial reproduction of six female pikeperch in preseason according to protocol described by Ljubobratović et al. (2021). The eggs of three females were fertilized with the sperm of pikeperch and the rest with sperm of Volga pikeperch. Half of the eggs of each group was submitted to the triplodization induction via hydrostatic pressure shock as described by Káldy et al. (2021). Following hatching all larvae from each group were mixed. At 6 days post-hatch, larvae were stocked in a larviculture recirculation system. Thus, in total four duplicate groups were formed: diploid (D), triploid (T), hybrid diploid (HD), hybrid triploid (HT). The trial lasted 40 days, in a temperature range of 16 ± 0.5 ºC and a light regime of 14:10 L:D. Larvae were fed with freshly hatched and enriched Artemia nauplii and starter feeds, finally weaned at 32 DPH. Sample measurement of body weight and length were performed on a weekly basis while all larvae were counted at the end of the trial and evaluated for the presence of swim bladder inflation.
Results
Chromosome analysis showed that the triploids were free of the presence of mosaic structures in the sample. Condition factor was significantly affected by triploidization being lower in triploids. Juvenile yield in form of swim bladder inflated juveniles per volume of rearing unit was significantly affected by hibridization. Likewise, hybridization had a significant effect on the percentage of swim bladder inflated fish.
Discussion
Hybrid groups showed enhanced larviculture performance in terms of production of fish with inflated swim bladder. With respect that the larviculture survival is the main bottleneck for the upgrade of pikeperch farming, this improvement might be beneficial for the sector and thus further evaluated in future studies. Triploidization did not yield positive results in in this study, however should be evaluated in more appropriate nutritional regimes.
Acknowledgements
This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement (Grant number: 871108 (AQUAEXCEL3.0).
Reference
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