Relationship between survival and body size of age-0 Pacific bluefin tuna Thunnus orientalis reared from eggs in sea cages during winter
2018
Higuchi, K. (Seikai National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Nagasaki, Nagasaki (Japan)) | Yoshikawa, S. | Hamasaki, M. | Baba, K. | Sakurai, K. | Norita, T. | Miyagishima, S. | Yamashita, S. | Takashi, T. | Gen, K. | Oka, M.
High mortality of age-0 hatchery-reared Pacific bluefin tuna (PBT) frequently occurs in sea cages during winter, particularly in fish farms around northern Kyushu in Japan. The hatchery-reared PBT are usually smaller than wild captured fish, suggesting that body size would be related to survival during winter. To reveal the relationship between survival and body size during winter, we examined survival and growth of age-0 PBT reared from fertilized eggs obtained in June (large-size group) and August (small-size group) in sea cages. The survival rate of age-0 PBT in the large-size group, after transfer from indoor tanks to sea cages till the next spring, was higher than the small-size group. High mortality occurred in PBT juveniles in the small-size group during winter, which showed a correlation with a decrease in water temperature. Moreover, the body size of large-size group was significantly larger than that of small-size group during the experimental period. These results suggest that body size is a critical factor affecting the survival of age-0 PBT during winter.
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