Aquaculture is one of the largest industries in Norway and is expected to grow in the future. Atlantic salmon (Salmo salar) is one of the most recognised and valuable seafood products among salmonids in the world along with rainbow trout (Oncorhynchuss mykiss), which also has high demand. However, variation in oocyte quality is one of the main constraints for a sustainable production in aquaculture industry. Efficient production is relying on good gamete quality. Due to limited knowledge and lack of reliable methods in production facilities to predict oocyte quality in salmonids at the time of spawning, sub-optimal oocytes are not usually detected until later in the process. This increases the wastage of valuable spermatozoa, oocytes and incubator capacity, as well as increases the risk of contamination that leads to higher mortality. Therefore, enhanced knowledge on oocyte quality criteria would contribute to a better reproductive success in the aquaculture industry.
Thus, the approach in this project is to reveal good criteria for practical and applicable determination of quality in oocytes which enables to predict the fertilisation success. In other words, oocyte quality should be determined in the oocytes once released from the female fish and prior to the fertilisation process. Therefore, this study will be focused on physio-chemical properties in the oocyte and its ovarian fluid to evaluate the quality in oocytes. This project will contribute towards the goal of the Norwegian aquaculture industry and to the salmonid producers by bringing new insight to the field of reproduction in fish. The project will create value to salmon egg producers through increased salmon egg production and allow for operational cost efficiency in egg production.
Due to limited knowledge and lack of reliable methods in production facilities to predict oocyte quality in salmonids at the time of spawning, sub-optimal oocytes are not usually detected until later in the process. This increases the wastage of valuable gametes & incubator capacity, as well as increases the risk of contamination that leads to higher mortality. Thus, the approach in this project is to reveal good criteria for practical and applicable determination of oocyte quality in oocytes which enables to predict the fertilisation success. The term oocyte here is used for both un-ovulated oocytes and ovulated ova. Traditionally oocytes are collected from salmonids directly from the ovaries, after slaughter, but can also be obtained by stripping. In this study we will be focusing on physio-chemical properties in the oocyte and it's ovarian fluid to evaluate the quality in oocytes. In addition quality analysis will be conducted and compared in oocytes and ovarian fluid in natural spawning and off-season. All the experiments will be performed using oocytes from 24 females. The following analyses will be performed: lipidomics analysis by UPLC-MS/MS, cortisol level by ELISA , energy level in oocytes by bioluminescence assay, protein identification and quantitation by nano liquid chromatography high resolution accurate mass spectrometry analysis, aspartate aminotransferase enzyme activity by colorimetric assay, pH level and osmolarity in ovarian fluid. Visual inspection of lipid globules in oocytes will be performed using fluorescence/confocal microscope. The results will be further assessed with fertilisation trials using the same number of females. After in vitro fertilization, eggs will be incubated in a multi-incubator system at SINTEF Ocean, and egg quality parameters will be assessed during embryogenesis until hatching. All parameters will be analysed using multivariate statistics to identify key markers for good quality oocytes.