Timing to promote initial swimbladder inflation by surface film removal in Pacific bluefin tuna,Thunnus orientalis (Temminck and Schlegel), larvae |
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| Authors: | Michio Kurata Manabu Seoka Yasunori Ishibashi Tomoki Honryo Shigeru Katayama Kenji Takii Hidemi Kumai Shigeru Miyashita Yoshifumi Sawada |
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| Institution: | 1. Ohshima Experiment Station, Fisheries Laboratory, Kinki University, Kushimoto, Japan;2. Toyama Experiment Station, Fisheries Laboratory, Kinki University, Imizu, Japan;3. Department of Fisheries, Faculty of Agriculture, Kinki University, Nara, Japan;4. Ohshima Station, Fish Nursery Center, Kinki University, Kushimoto, Japan;5. Uragami Experiment Station, Fisheries Laboratory, Kinki University, Nachikatsuura, Japan;6. Shirahama Experiment Station, Fisheries Laboratory, Kinki University, Shirahama, Japan |
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| Abstract: | This study investigated the optimal timing of day to promote initial swimbladder inflation (ISI) for improved Pacific bluefin tuna (PBT), Thunnus orientalis, larval survival. Larval swimbladder inflation frequency was compared based on three experiments using different time schemes of surface film removal (SFR) from 3 to 9 days post hatch (dph). SFR was conducted from 05:00 to 19:00 hours (light period: S.5–19), 19:00 to 05:00 hours (dark period: S.19–5), 08:00 to 19:00 hours (S.8–19) and the entire day (S.24) in Experiment 1; from 08:00 to 19:00 hours (S.8–19‐E2), 08:00 to 13:00 hours (S.8–13), 13:00 to 19:00 hours (S.13–19) in Experiment 2; and from 13:00 to 16:00 hours (S.13–16), 16:00 to 19:00 hours (S.16–19), 18:00–19:00 hours (S.18–19) in Experiment 3. The swimbladder inflation frequency at the experiment termination (9 dph) was significantly higher (P < 0.001) in S.24 (91.1 ± 5.7%), S.5–19 (92.2 ± 5.1%) and S.8–19 (93.3 ± 3.4%) than in S.19–5 (11.1 ± 5.1%) in Experiment 1, and remarkably higher in S.8–19‐E2 (81.7%) and S.13–19 (88.3%) than in S.8–13 (0.0%) in Experiment 2, and significantly higher (P < 0.001) in S.16–19 (84.4 ± 5.1%) and S.18–19 (70.0 ± 12.0%) than in S.13–16 (7.8 ± 3.9%) in Experiment 3. These results suggest that the optimal timing to promote larval ISI by SFR is a few hours before the end of light period (16:00–19:00 hours) from 3 to 9 dph. |
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| Keywords: | bluefin tuna
Thunnus orientalis
larvae swimbladder survival |
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