2001 Fiscal Year Final Research Report Summary
Sensory responses to environmental changes and behavior controls of bluefin tuna larva and juvenile
| Project/Area Number |
11460091
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General fisheries
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| Research Institution | Hiroshima University (2000-2001)
Kagoshima University (1999) |
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Principal Investigator |
NAMBA Kenji Hiroshima University, Faculty of Applied Biological Science, Professor, 生物生産学部, 教授 (10034472)
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| Co-Investigator(Kenkyū-buntansha) |
ANRAKU Kazuhiko Kagoshima University, Faculty of Fisheries, Associate Professor, 水産学部, 助教授 (50274840)
KAWAMURA Gunzo Kagoshima University, Faculty of Fisheries, Professor, 水産学部, 教授 (30041718)
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| Project Period (FY) |
1999 – 2000
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| Keywords | bluefin tuna / sensory organs / morphogenesis / bumping / juvenile / retinomotor response / visual disorientation / larva / oxygen consumption |
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| Research Abstract |
Experiment 1 : At hatching eleutheroembryos were characterized by well developed mechanoreceptors ; the inner ear, oval-shaped otic vesicle, with two otoliths suspended in it and the siliated otic vesicle epithelium ; a pair of large free neuromasts with cilia and cupulae behind the eyes. Three semicircular canals and ossfication were completed at 8d. The retinae were innervated at 14h, lenses of a single layer were formed and the retina was layered at 18h, single cones and horizontal cells were differentiated in the retina at 2d, and the eyes were well pigmented at 3d. The olfactory pits opened and olfactory epithelium consisted of the ciliated receptor cells, microvillous receptor cells and ciliated nonsensory cells at 2d.
Experiment 2 : In bluefin tuna culture, a high mortality of juveniles is caused by bumping into the tank and net-pen walls at dawn. This bumping can possibly be attributed to visually disoriented behavior of the fish. To examine this possibility, the authors carried
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out retinomotor response experiments with juvenile bluefin tuna (50.7-96.8 mm total length, at which they were transferred from a indoor tank to a sea net-pen) and measured ambient light intensity at the culture site at dawn. The light intensity at which the transition from scotopic to photopic vision takes place was 7.52 lx and the time taken by the transition was 15 min. At dawn, the ambient light intensity rapidly increased from scotopic light intensity level and attained photopic light intensity level in 10 min. This incompatibility of the retinal adaptation with the change in the ambient light intensity could cause the visual disorientation of the fish. It is therefore possible that the visually disoriented juveniles cannot control their high power swimming and thus bump into the walls at dawn.
Experiment 3 : Feeding rates of the larvae were estimated at 85-580 rotifer per day on 3-11 days after hatching (DAH) and at 150-1000 prey larvae, newly hatched fish larvae of other species, per day on 10-30 DAH (7-25 mmTL). The oxygen consumption of the larvae on 1-29 DAH ranged from 0.035 to 8.2 μlO_2 individual-1 min-1. The energy balance of the larvae calculated from the feeding rate and the oxygen consumption changed from positive to negative. When the prey larvae were used as a substitute for the rotifers, the energy balance was positive. However, the balance changed to negative again when the prey larvae continued to be fed over 30 DAH. Less
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Research Products
(2 results)
