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Tokihiko Okada Yuki Sakurai Tomoki Honryo Masato Kawahara Yasunori Ishibashi 《Aquaculture Research》2020,51(7):3017-3024
High levels of mortality occur in large net‐cage culture of Pacific bluefin tuna (PBF) Thunnus orientalis due to poor growth on commencement of sea‐cage culture obstructing the mass production of fingerlings. Therefore, we carried out this study to develop a countermeasure by using small sea cages (square with 13‐m sides). PBF juveniles were directly transferred to a 30‐m‐diameter cage (control) and compared them to fish transferred to small sea cages for 12 days before being merged into another 30‐m‐diameter cage. The survival rate, growth performance and potential factors increasing mortality were examined. The results of our study showed that survival rate in small sea cages was approximately 20% higher than that of the control. Poor growth also occurred in the small sea cages; however, its frequency and daily mortality rate were half those in the control. In addition, growth performance such as specific growth rate and weight gain of PBF juveniles in small sea cages significantly increased compared to the control. These results suggest that using small sea cages could be an effective countermeasure for poor growth, which may mitigate the high‐mortality conditions of current sea‐cage culture systems for PBF. 相似文献
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Tsuchiyama A Uesugi M Matsushima T Michikami T Kadono T Nakamura T Uesugi K Nakano T Sandford SA Noguchi R Matsumoto T Matsuno J Nagano T Imai Y Takeuchi A Suzuki Y Ogami T Katagiri J Ebihara M Ireland TR Kitajima F Nagao K Naraoka H Noguchi T Okazaki R Yurimoto H Zolensky ME Mukai T Abe M Yada T Fujimura A Yoshikawa M Kawaguchi J 《Science (New York, N.Y.)》2011,333(6046):1125-1128
Regolith particles on the asteroid Itokawa were recovered by the Hayabusa mission. Their three-dimensional (3D) structure and other properties, revealed by x-ray microtomography, provide information on regolith formation. Modal abundances of minerals, bulk density (3.4 grams per cubic centimeter), and the 3D textures indicate that the particles represent a mixture of equilibrated and less-equilibrated LL chondrite materials. Evidence for melting was not seen on any of the particles. Some particles have rounded edges. Overall, the particles' size and shape are different from those seen in particles from the lunar regolith. These features suggest that meteoroid impacts on the asteroid surface primarily form much of the regolith particle, and that seismic-induced grain motion in the smooth terrain abrades them over time. 相似文献
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We measured the shelter effect of model windbreaks in a wind tunnel before and after adjustment thinning based on methods
for managing overcrowded windbreaks. One of the aims of this experiment was to determine whether or not the actual thinning
done on an actual windbreak would sustain the shelter effect. The shelter effects were evaluated based on the critical wind
speed and the shelter distance. Six model windbreaks were set to model a windbreak after the thinning (AT1–6) and one was
set to model it before the thinning (BT). In models AT1–3, the trees in the middle part of the windbreak were cut and the
trees in both the windward and leeward parts were left. AT1 and AT2 were models that reproduced the actual windbreak after
the thinning. In the other three models (AT4–6), which were set as additional thinning models based on AT3, trees in both
the windward and leeward parts were cut. The thinning ratios of these models ranged from 21% (AT1) to 84% (AT6). The shelter
effects of AT1–3 were sustained or only slightly decreased compared with that of BT. The shelter effects of AT4 (thinning
ratio of 63%) and AT5 (79%) were the highest among all of the models. From these results, it was confirmed that the thinning
done on an actual windbreak was able to sustain the windbreak’s shelter effect. If the trees at the edges are not felled,
the shelter effect of the windbreak can be sustained or improved, even if the thinning is heavier than AT2. 相似文献
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Pramod DHAKAL Nobuo TSUNODA Rie NAKAI Tomoki KITAURA Takehiro HARADA Masahiro ITO Kentaro NAGAOKA Yuko TOISHI Hiroyuki TANIYAMA Watanabe GEN Kazuyoshi TAYA 《Journal of Equine Science》2011,22(2):29-36
Changes in follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin,
immunoreactive(ir)-inhibin, testosterone, estradiol-17β, and insulin-like growth factor
(IGF)-I in Thoroughbred stallions along with changes in prolactin secretion in geldings
were studied. The correlations of day-length with changes in the concentrations of these
hormones were also studied. Five stallions and thirteen geldings were employed to draw
blood samples in monthly basis and radioimmunoassay was performed to measure these
hormones. All hormones showed a seasonal pattern, the levels being highest during the
breeding season and lowest during the winter months. Most of the hormones were at their
highest concentration during the month of April, the mid of spring in northern hemisphere.
The concentration of circulating IGF-I also demonstrated seasonality, the peak lying on
the month of April. The plasma concentration of prolactin also increased during the
breeding season. This phenomenon was similar both in stallions and geldings although
geldings had lower concentration than that of stallions. The changes in concentration of
prolactin in stallions and geldings correlated more towards the day-length than towards
the temperature. These results clearly indicate the seasonality of pituitary and gonadal
hormones of Thoroughbred stallions, the activity being highest during the month of April
and May of the breeding season. 相似文献
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Hiroyuki Mizuta Tomoki Kai Katsuhiro Tabuchi & Hajime Yasui 《Aquaculture Research》2007,38(12):1323-1329
Responses of the sporophytes of Laminaria japonica to blue, red and white lights were investigated using segments, discs and whole plants. The relative growth rate with regard to the blade's length and width showed no difference among the light conditions during 2 weeks of culturing. On the contrary, the elongation rates of the stipe and the holdfast were 1.7–2.5 times higher under red light than that under white light as a control. Callus formation in the segments was also promoted more under red light conditions than under white or blue light. Blue light irradiation resulted in a 48% and 12% decrease in the relative growth rate of the stipe and the holdfast, respectively, in comparison with the control. When sporophyte discs were cultured for 10 weeks, all discs formed zoosporangial sori 2–3 weeks earlier under blue light than under white light. However, red light inhibited the formation of zoosporangia. Indoleacetic acid (IAA) oxidase activity was about two‐fold higher under blue light than under red light, suggesting that the difference in response between the blue and red light conditions is related to the internal IAA level of the tissues. The developmental, reproductive and morphological effects of blue and red lights will be useful for the artificial control of the life cycle of Laminaria plants and for the development of more efficient cultivation techniques. 相似文献
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Influence of swimbladder inflation failure on mortality,growth and lordotic deformity in Pacific bluefin tuna,Thunnus orientalis, (Temminck & Schlegel) postflexion larvae and juveniles 
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下载免费PDF全文 Michio Kurata Yasunori Ishibashi Manabu Seoka Tomoki Honryo Shigeru Katayama Hiromu Fukuda Kenji Takii Hidemi Kumai Shigeru Miyashita Yoshifumi Sawada 《Aquaculture Research》2015,46(6):1469-1479
This study examined the influence of swimbladder inflation (SBI) failure on mortality (Experiment 1), lordotic deformity (Experiment 2) and growth (Experiment 1, 2) in Pacific bluefin tuna, Thunnus orientalis, postflexion larvae and juveniles by producing larvae lacking inflated swimbladders. Experiment 1 was conducted for postflexion larvae to juveniles (from 18 to 30 days‐post‐hatch; dph). Mortality was not significantly different between the fish with (WIS) and without (WOIS) inflated swimbladders. Standard length (SL) and body weight (BW) were significantly smaller in WOIS than WIS. Moreover, the SBI was found in WOIS after postflexion stage. In Experiment 2, two examination trials were conducted on SBI, vertebral deformity and growth for juvenile stage. Lordotic deformities were found neither in the WOIS nor in the WIS. Although SL and BW were significantly smaller in WOIS than WIS at 22 dph, after 37 dph no significant differences were found between them. The results of Experiment 1 and 2 indicate that SBI failure causes growth retardation until juveniles of 30 dph; however, it does not cause growth retardation in juveniles after 37 dph and mortality of postflexion larvae and juveniles. Moreover, SBI failure did not cause lordotic deformity in PBT differently from many other fish. 相似文献