Effect of washing unfertilized eggs with isotonic solution on egg viability in chum salmon Oncorhynchus keta and masu salmon Oncorhynchus masou
2016
Ohmoto, K. (Tohoku National Fisheries Research Institute, Fisheries Research Agency, miyako, Iwate (Japan). Research Center for Coastal Fisheries and Aquaculture, Salmon Resources Research Group) | Ono, I. | Hirasawa, K. | Kawana, M. | Yoshimizu, M.
The effectiveness of washing eggs with an isotonic solution as a measure for preventing fish pathogens was examined at a practical scale in cultured salmonid fish. The effectiveness of washing on the number of viable bacteria infecting eggs at the eyed stage of development, as well as the survival rates of hatched fry, were examined in masu salmon Oncorhynchus masou and chum salmon O. keta. In masu salmon, the number of bacteria on the egg surface before washing was approximately 10E4 CFU/mL, which decreased to 10E2 CFU/mL after washing. In chum salmon, the number of bacteria was 10E3 CFU/egg before washing, which decreased to 10E1 CFU/egg after washing. The findings showed that washing was effective for reducing the number of bacteria on eggs. In the case of shower washing with stirring, the fertility rate decreased due to physical shock. The mortality of hatched fry was significantly lower in breeding ponds stocked with fry from eggs that had been subjected to washing, suggesting that it was effective for increasing fry survival in aquaculture ponds. For masu salmon, a combination of rinsing and showering without stirring is proposed, whereas for chum salmon, showering without stirring is proposed.
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