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Volume 68, Issue 4
Displaying 1-11 of 11 articles from this issue
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Original paper
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Kazuhiro Ura, Takahiro Gotoh, Yudai Kitano, Osamu Nishimiya, Yasuaki T ...2020 Volume 68 Issue 4 Pages 309-315
Published: 2020
Released on J-STAGE: December 20, 2021
JOURNAL FREE ACCESSMajor yolk protein (MYP), a member of the transferrin protein superfamily, forms yolk granules in the eggs of sea urchins and is stored in nutritive phagocytes within the gonads and coelomic fluid of both sexes. In this study, we purified and biochemically characterized MYP from the eggs (EGMYP) and coelomic fluid (CFMYP) of the sea urchin Strongylocentrotus intermedius. The molecular masses of purified EGMYP and CFMYP via gel filtration were 595 and 700 kDa in an intact state, respectively, and both are glycolipoproteins. EGMYP and CFMYP are capable of binding folic acid, suggesting that both proteins are involved in the transport of folic acid into oocytes, where it is a nutrient source for the development of embryos.View full abstractDownload PDF (389K) -
Tomoki Honryo, Honami Tsukada, Tokihiko Okada, Yasuo Agawa, Michio Kur ...2020 Volume 68 Issue 4 Pages 317-326
Published: 2020
Released on J-STAGE: December 20, 2021
JOURNAL FREE ACCESSTo develop more efficient culture techniques of Pacific bluefin tuna (PBF, Thunnus orientalis), it is important to manage fish welfare. Blood examination could be a useful tool to check fish health condition. This study investigated the effect of common rearing factors such as anesthesia, excess exercise and feeding on blood properties and chemistries of cultured PBF juvenile. Results of this study showed that anesthesia treatment significantly induced blood acidosis and red blood cell (RBC) swelling, thus anesthesia should not be used for PBF juveniles to examine their health condition. Even though excess exercise and feeding did not influence blood pH, partial pressure of O2 or CO2, RBC count was significantly decreased and mean corpuscular volume increased after excess exercise and feeding. In addition, electrolyte concentrations such as Na+, Cl－ and Ca2+ in the blood increased after excess exercise and feeding. Hence, this study suggests that blood collection from PBF juveniles should be conducted before feeding and that anesthesia should be avoided to minimize negative physiological effects.View full abstractDownload PDF (923K) -
Yoshitsugu Masuda, Kouta Miyamoto2020 Volume 68 Issue 4 Pages 327-335
Published: 2020
Released on J-STAGE: December 20, 2021
JOURNAL FREE ACCESSDespite Japanese smelt Hypomesus nipponensis being an important species for inland fisheries in Japan, practical aquaculture method of rearing their larvae has yet to be established. Stock enhancement has been conducted in almost every case by releasing eyed eggs or larvae immediately after hatching. One of the hindrances to establishing an effective rearing system for Japanese smelt is the difficulty in determining which food is appropriate for the larva development stage. For this study, we used rotifer (Thai-type) and commercial dry pellets for rearing of Japanese smelt larvae. At 72 days after hatching, 67.8% of juvenile Japanese smelt survived, while the average total length of fish was 29.9 mm. These results demonstrate that Japanese smelt can be reared effectively using only one type of live and formulated food.View full abstractDownload PDF (1131K) -
Youhei Washio, Mitsuki Ohama, Halle Suzuki, Ryosuke Kanatsu, Dong-in K ...2020 Volume 68 Issue 4 Pages 337-350
Published: 2020
Released on J-STAGE: December 20, 2021
JOURNAL FREE ACCESSWith the development of new marine fin-fish breeding technologies, the risk that new breeds, especially genetically-modified fish, might escape and disperse into natural environments was considered high. To avoid this risk, these breeds were kept in terrestrial tanks. It was considered important to prevent not only new fish breeds themselves, but also their gametes, from escaping into the sea. To inactivate such gametes, we conducted a test using ultraviolet (UV) irradiation and freshwater on the sperm and eggs, respectively, of red sea bream (Pagrus major) and determined treatment effectiveness by means of the hatching ratio. In a petri dish test, UV irradiation inactivated sperm fertility at a dose of 150 mJ/cm2, with appropriate dilutions. UV irradiation devices attached to the actual broodstock rearing tanks were also able to completely inactivate sperm fertility at a dose of 370 mJ/cm2. In a freshwater-only treatment, a small number of eggs were able to survive treatments of less than 13 hours. Freshwater heated to more than 40°C could inactivate eggs completely within a short time (5 minutes). Based on these results, we proposed a land-based tank with flow-through (open) system that would prevent the spread of red sea bream-gametes to the sea.View full abstractDownload PDF (2494K) -
Yasuhiro Fujioka, Takeshi Kikko, Morihito Nemoto2020 Volume 68 Issue 4 Pages 351-356
Published: 2020
Released on J-STAGE: December 20, 2021
JOURNAL FREE ACCESSWe designed a simple apparatus for counting hatchlings without artificial stimulus of light in order to examine the timing of hatching in honmoroko Gnathopogon caerulescens. Using this apparatus, under the natural photoperiod condition, almost all the eggs synchronously hatched within 2 hours after sunset. A 750 lx light condition delayed the hatching and initiating darkness four hours earlier than that of the natural photoperiod resulted in accelerated hatching. These results indicate that light is a significant factor regulating hatching and the change from light to dark condition by sunset is a cue synchronizing hatching. We need to pay attention to the light condition of eggs during the transportation.View full abstractDownload PDF (624K) -
Kazutoshi Okamoto2020 Volume 68 Issue 4 Pages 357-366
Published: 2020
Released on J-STAGE: December 20, 2021
JOURNAL FREE ACCESSTwo series of laboratory experiments were conducted to examine the effects of rearing water on the survival and molting interval of the Japanese giant spider crab Macrocheira kaempferi, during its early life stages. For the first experiment, the effects of selected antibiotics (ANTIB), alone or in combination [Penicillin G potassium sulfate 100 ppm (P), Streptomycin sulfate 50 ppm (S), Chloramphenicol 25 ppm (C), P＋S, P＋C, S＋C (SC), P＋S＋C, and no ANTIB]. were examined during the megalopa (M) and 1st crab (C1) stages. The ANTIB combination SC was found to have marked effects on survival. In the second experiment, hatching larvae were reared until reaching the C2 stage under different water conditions: surface seawater (Su), 397-m-deep seawater (397D), 687-m-deep seawater (687D), Su with SC, 397D with SC, and 687D with SC. The ANTIB combination SC was observed to have marked effects on survival and 687D was found to be suitable for rearing the larvae. The findings of this study revealed that survival of the early stages of the crab M. kaempferi exposed to the ANTIB combination SC (M and C1 survival rates: 15.5%-50.0%) was greater compared with that reported by previous studies (survival rates: 0%-5.9%).View full abstractDownload PDF (1221K)
Short Paper
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Microbial communities of the eelgrass Zostera marina bed in Tanoura Bay, Shimoda, Shizuoka in summerChia-Hui Chen, Yusuke Tanaka, Terukuni Kozaki, Shiro Itoi, Haruo Sugi ...2020 Volume 68 Issue 4 Pages 367-370
Published: 2020
Released on J-STAGE: December 20, 2021
JOURNAL FREE ACCESSMicrobial communities of eelgrass (Zostera marina) leaves, seawater and sediments in the eelgrass bed, Tanoura Bay, Shimoda, Shizuoka in summer were examined by the clone library and qPCR methods. Direct counts of bacteria were 2.1×106-6.9×106 cells/cm2 on the eelgrass leaves, 3.1×106-1.5×107 cells/ml in seawater and 1.2×108-2.4×108 cells/g in sediments. The predominant clones closely related to Pseudomonadaceae, Rhodobacteriaceae and Flavobacteriaceae accounted for 11.1-14.3% of all 315 clones in the eelgrass bed. Fish pathogens were not detected in six 16S rDNA-clone libraries. The sulfate-reducing bacteria (SRB) were 2.5×105-2.8×105 copies/g in sediments, corresponding to the level of unpolluted area. These results suggest that the eelgrass bed in Tanoura Bay does not currently pose any particular problem as a fish habitat.View full abstractDownload PDF (297K) -
Daisei Ando, Yoshitaka Sasaki2020 Volume 68 Issue 4 Pages 371-374
Published: 2020
Released on J-STAGE: December 20, 2021
JOURNAL FREE ACCESSThe relationship between the initial egg size and subsequent body weight of fry in chum salmon was investigated from 0 to 49 days after emergence. The size of emergent fry depended on the initial egg size. This relationship was observed until the 35 days after emergence, but thereafter there was no correlation between initial egg size and body weight of fry due to egg size independent growth. This suggests that rearing in the hatchery for > 1 month from emergence may reduce the impact of egg size on fry size of chum salmon.View full abstractDownload PDF (418K)
Note
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Kensaku Azuma, Kikuo Horioka, Masayuki Ohgi, Tsuyoshi Iyota, Isao Mats ...2020 Volume 68 Issue 4 Pages 375-382
Published: 2020
Released on J-STAGE: December 20, 2021
JOURNAL FREE ACCESSIn the Shimanto River, the native ayu, Plecoglossus altivelis altivelis is generally superiority in number against the released artificial one; therefore, ascending numbers of juvenile ayu in the river have an influence upon the population dynamics. Juvenile ayu swimming upstream was counted through visual observations (9-10 times during March-May) and underwater videos (25-30 times during Februay-May) in the lower reaches of the Shimanto River from 2015 to 2019. Fishes began migrating upsteam during early February to mid-March when water temperatures had increased to approximately 10°C; the number of fishes peaked between early March and mid-April when the temperatures had gradually increased from approximately 12°C to 18°C. The number of fishes and their anuual differences were larger when counted by visual observation than by using a video camera. However, the mean numbers of fish were high in 2015, 2017, and 2018, whereas they were low in 2016 and 2019, irrespective of the counting methods. Furthermore, a significant correlation between the annual catches of ayu and the mean number of fish observed during the study period was evident. The simple methods used in this study shoud effectively and conveniently predict the relative ascending numbers of wild ayu.View full abstractDownload PDF (1300K)
Erratum
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2020 Volume 68 Issue 4 Pages 384
Published: 2020
Released on J-STAGE: December 20, 2021
JOURNAL FREE ACCESS -
2020 Volume 68 Issue 4 Pages 385
Published: 2020
Released on J-STAGE: December 20, 2021
JOURNAL FREE ACCESS
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