Predicting population's oocyte maturation competence and evaluating individual's latency time using in vitro oocyte maturation in pikeperch (Sander lucioperca)

Artificial reproduction of pikeperch (Sander lucioperca) is characterized by the unpredictability of latency time (LT) as well as the variability of egg quality depending on the time of hormonal stimulation. To predict latency time and thus enhance fertilization outcomes, the present study evaluated whether in vitro maturation techniques could be utilized to assess the status of oocyte maturation competence (OMC). Oocyte samples from nine pond-reared females originating from the Czech Republic (CZECH) and 12 intensively cultured females originating from river Ko spexpressioncing diexpressioneresis ro spexpressioncing diexpressioneresis s (HAKI) were catheterized at the time of hormonal stimulation and cultured in L15 medium supplied with 100 ng/mL of DHP. The stage of final oocyte maturation (FOM) was monitored both in vivo and in vitro and egg quality features were evaluated. HAKI group was characterized by larger oocytes at the time of stimulation (934.4 +/- 32.9 mu m vs. 860.0 +/- 22.7 mu m), as well as higher embryo survival (77.7 +/- 10.4% vs 53.5 +/- 28.8%), suggesting that artificial reproduction was performed prematurely for CZECH group. Oocytes from HAKI fish displayed a higher share of maturing oocytes (41.4 +/- 9.1% vs. 13.8 +/- 17.6%) and in all samples germinal vesicle breakdown was noticed, while in the CZECH group it was so only in oocytes of one fish. With respect that all fish ovulated after the gonadoliberin stimulation, gonadotropin-regulated OMC is assumed. A correlation was found between the in vivo and in vitro LTs in the HAKI group only (r = 0.791, P = 0.002), indicating a certain autonomy of ovarian follicle of other parts of the physiological axis after completed OMC. The in vitro techniques show great promise for practical application in hatcheries to evaluate the aptness for hormonal stimulation on both individual and population levels.

Automated summary

In vitro maturation techniques have the potential to predict latency time and improve fertilization outcomes in pikeperch artificial reproduction. The study found that artificial reproduction may have been performed prematurely for the pond-reared fish from the Czech Republic. Fish from the intensively cultured group from Hungary showed larger oocytes at the time of stimulation and higher embryo survival rates. There was a correlation between in vivo and in vitro latency times in the Hungarian group.