Introduction: Hormone application by intramuscular or intraperitoneal is a standard method in many fish to induce ovulation of eggs as much as equally. However, the success of the hormonal injections depends on many factors like timing, environment, handlings stress. The aims this study are to increase egg quality and received amount of egg per kg female at a synchronized time in marine fish species.
Method: European seabass (Dicentrarchus labrax) was used as a model fish. Females were injected intramuscularly by 30 µg/kg BW LHRHa, single shot (600-650 µ oocyte size) in Control Group (CG) and this group representing a routine culture method. Same dose of hormone application to females in examination group (EG) was carried out by ovarian lavage method using poultry egg albumin (as a hormone carrier). In the EG, the sperm collected from selected three males was inseminated (0.5 mL per ovarium per kg) to two female breeders 54 hours after hormone application (Müller et al. 2018). The experiment was tested in triplicate tanks. Eggs were collected, weighed and then placed in incubator tanks for hatching. Embryonic developments were checked separately in the cooled incubator at 14.5°C for 4 days (Panini et al 2001). Hatching rates were checked in incubation tanks and larvae were distributed for larval rearing condition. Finally, pGSI, larval survival rates were calculated after 28 days of larval weaning. This study was funded by TÜBITAK 121N529.
Results: Except the fertilization and larval survival rate all other parameters were better in EG than CG but not significantly different (P>0.05). In EG and CG no significant differences found in fertilisation (72.28% and 75.08% respectively) and larval survival rate (24.36% and 26.38 respectively) either (P>0.05). Latency time of both groups after hormone application to spawning occurrence was similar, between 38-92 hours according to oocyte size and readiness of the female.
Application of ovarian lavage hormone method gave successful results with better results of pGSI and viable egg ratio. This method can be applied to more sensitive fish under anaesthesia.
Literature:
Müller et al. 2018. https://doi.org/10.1016/j.aquaculture.2017.09.025
Panini et al. 2001. https://doi.org/10.1023/A:1014261830098