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Volume 64, Issue 4
Displaying 1-9 of 9 articles from this issue
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Original paper
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Takashi Iwasaki, Sho Mizuta, Takayuki Kogane, Jun Satoh, Shigeki Dan, ...2016 Volume 64 Issue 4 Pages 349-358
Published: December 20, 2016
Released on J-STAGE: December 20, 2017
JOURNAL FREE ACCESSTo understand the process of initial swim bladder inflation, swim bladder development was histologically examined in larvae of longtooth grouper, Epinephelus bruneus, and red spotted grouper, Epinephelus akaara. The posterodorsal wall of the larval digestive tract of both species protruded, the swim bladder formed, and the pneumatic duct connected the swim bladder to the digestive tract during 6-10 days after hatching (DAH) (3.6-5.0 mm standard length, SL) and 5-8 DAH (3.0-3.3 mm SL) in longtooth and red spotted grouper larvae, respectively. Larvae of both species were reared in tanks with or without treatments to remove oil film from the water surface. In both species, more larvae developed inflated swim bladders in the tank with the oil-film-removal treatment than in the tank without, and the numbers of larvae with inflated swim bladders increased from 6 to 9 DAH (3.2-3.9 mm SL) and from 5 to 8 DAH (2.6-3.6 mm SL) in longtooth and red spotted grouper, respectively. Our results indicated that larvae inflated their swim bladders by gulping air from the water surface, and that timing of initial swim bladder inflation was 4-5 days in the early life stage by 10 DAH.View full abstractDownload PDF (611K) -
Jeonghyeon Cho, Yutaka Haga, Yuji Kamimura, Atsushi Akazawa, Akira Ito ...2016 Volume 64 Issue 4 Pages 359-370
Published: December 20, 2016
Released on J-STAGE: December 20, 2017
JOURNAL FREE ACCESSSurvival rate of PBT from hatch to juvenile is less than 2%. One reason of lower survival could be due to limited supply of prey fish such as Spangled emperor Lethrinus nebulosus and Japanese parrotfish Oplegnathus fasciatus. In order to solve this problem, this study aimed to determine suitable formulated commercial diet to replace prey fish. We evaluated the dietary utility of CM1, CM2 and CM3, commercially available, and control prey Spangled emperor fish larvae to Pacific bluefin tuna larvae and juveniles. PBT larvae at 21 days post-hatch with mean total length of 20.2 mm were fed prey fish larvae and the CM1 diet during the first four days of the feeding trial and weaned onto each diet to examine the effect of switching diets on feed acceptance. Survival and growth were compared after day 11 of the feeding trial. Among the test diet groups, the highest survival occurred for CM1, followed by CM2 and CM3. Of the groups, the CM3 group had significantly greater total length and body weight. These results suggest that PBT larvae and juveniles can readily acclimate to formulated commercial diets once they are successfully weaned onto a suitable formulated diet such as CM1.View full abstractDownload PDF (422K) -
Sho Kashio, Yusuke Yamana, Nami Furukawa, Ryouto Uekusa, Seiji Goshima2016 Volume 64 Issue 4 Pages 371-378
Published: December 20, 2016
Released on J-STAGE: December 20, 2017
JOURNAL FREE ACCESSAn investigation was conducted to determine the seasonal distribution patterns of the Japanese sea cucumber Apostichopus japonicus (green type) in Usujiri, Funka Bay of Hokkaido, Japan. Bimonthly SCUBA surveys was conducted from December 2009 to October 2010. Results showed that medium to large sized sea cucumbers (>100 mm in standard body length) showed significant seasonal change in distribution patterns. They were distributed on the upper surface of rocks and sandy seabed during low temperature season and retreated to the under surface of rocks and the bottom underneath rocks during high temperature season. Conversely, small sized sea cucumbers were distributed under surface of rocks and bottom underneath rocks year round. These results suggest that the sea cucumbers change microhabitats seasonally at this study site, and it is related to the individual body size.View full abstractDownload PDF (29K) -
Shanshan Jiang, Hiroko Iwashita, Osamu Arakawa, Tomohiro Takatani2016 Volume 64 Issue 4 Pages 379-390
Published: December 20, 2016
Released on J-STAGE: December 20, 2017
JOURNAL FREE ACCESSTo explore how light wavelength affects the growth of a dinoflagellate species and its production of paralytic shellfish toxin (PST), we examined the growth and PST production of Alexandrium catenella (Ac) cultured under monochromatic light. The Ac strain was cultured for 21 days under blue (470 nm), green (530 nm), or red (660 nm) LED irradiation (Blue, Green, and Red groups respectively). During the culture period, the cell density (Cd) increased rapidly in Blue and slowly in Red, while the cell volume (Cv) decreased in Blue, but gradually increased in Red. In Green, Cd increased slowly, but Cv decreased. Interestingly, the increase in the cell biomass per unit medium volume was similar in Blue and Red, suggesting that the cell biomass of Ac increases equally by either an increase in the cell number under blue light, or by an increase in the cell volume under red light. HPLC analysis for PST revealed that the amount of toxin produced per cell, cellular toxin concentration, and toxin content per unit medium volume were highest in Red, followed by Green, and then Blue; i.e., Ac produced more PST under red light than blue light, despite the equivalent increase in the cell biomass under both conditions.View full abstractDownload PDF (30K) -
Teruwo Morita, Makoto Kakinuma, Mizuho Fujii, Ami Imai, Akira Kurashim ...2016 Volume 64 Issue 4 Pages 391-398
Published: December 20, 2016
Released on J-STAGE: December 20, 2017
JOURNAL FREE ACCESSThe morphological characteristics of shoots of Zostera marina L. germinated at 7, 10, 15, 20, and 25 ℃ were examined in outdoor mesocosms to better understand the reproductive and vegetative strategies of perennial populations. Seeds were divided into two groups: those exposed to cold (vernalized group) and those left untreated (non-vernalized group). In the vernalized group, the germination rate was the highest at 15 ℃ and was higher than in the non-vernalized group. All seedlings developed into reproductive shoots 14 months after sowing. Numbers of new lateral and reproductive shoots were not significantly affected by germination temperature. The total number of spadices, the total number of branches per shoot and the inflorescence length of reproductive shoots were also not significantly affected by germination temperature in perennial-type Z. marina. In the vernalized group, the total number of spadices on the first branches was only significantly higher than the total number on the sixth branches in reproductive shoots. This finding suggests that the sexual and asexual propagation of perennial Z. marina shoots is almost unaffected by germination temperature and early growth.View full abstractDownload PDF (1372K)
Short Paper
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Tetsuo Morita, Tadashi Imai, Yoshihisa Yamamoto2016 Volume 64 Issue 4 Pages 399-402
Published: December 20, 2016
Released on J-STAGE: December 20, 2017
JOURNAL FREE ACCESSWe investigated the removal of the monogenean parasite Benedenia epinepheli and survival of commercially-reared host red-spotted grouper Epinephelus akaara under immersion at salinities (0-20 psu) at 28-29 ℃. Replicate samples of juvenile grouper did not die in salinities of 6 psu and above for 2 hours. All parasites were removed from fish at <10 psu. Immersion time required for the complete parasite removal in 6 and 8 psu waters was 30 and 120 minutes, respectively. Our results suggest immersion into 6 psu salinity water for 30 minutes is a practical and effective treatment to remove B. epinepheli without significant mortality.View full abstractDownload PDF (321K) -
Nariaki Inoue2016 Volume 64 Issue 4 Pages 403-405
Published: December 20, 2016
Released on J-STAGE: December 20, 2017
JOURNAL FREE ACCESSSurvival and growth rates of some marine fishes such as red-spotted grouper, E. akaara and false kelpfish, Sebastiscus marmoratus during early larval to juvenile stages have improved drastically by rearing fish in low-salinity water. Cultured longtooth grouper, Epinephelus bruneus, suffer from high mortality rates during larval stages and the growth rate of juveniles is poor. Low-salinity tolerance data are needed for E. bruneus larvae and juveniles as a first step to apply low-salinity water rearing to mass seed production. This study revealed changes in low-salinity tolerance in E. bruneus larvae and juveniles associated with development using a logistic regression model included in a generalized linear model (GLM). The median lethal salinity doses (LD50) of 24 h rearing based on the predicted death probability curves for GLM at the mid-larval (19-20 dph), late-larval (48-49 dph), early juvenile (68-69 dph), and late juvenile stages (335 dph) were 10.5, 14.2, 4.4, and 2.7 psu, respectively. Grouper larvae are probably less tolerant to low salinity than other coastal fish species such as olive flounder, Paralichthys olivaceus and sea bream, Pagrus major.View full abstractDownload PDF (253K)
Note
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Makoto Kaneko, Setsuko Maeda, Shoko Ojika, Saki Takahashi, Hajime Maed ...2016 Volume 64 Issue 4 Pages 407-412
Published: December 20, 2016
Released on J-STAGE: December 20, 2017
JOURNAL FREE ACCESSFish meal has become more expensive in recent years. This study examined how a diet of kelp powder substituted for fish meal affected the growth performance of red sea bream Pagrus major, which is one of the most economically valuable marine fish in Japan, with the aim of reducing the amounts of fish meal in their diet. Red sea breams were fed either a diet of fish meal that was in part (10%) substituted by powdered kelp (kelp group) or fish meal (control group) for 28 days. The mean initial body weight was 10.3±1.8 g for the kelp diet group and 9.9±2.9 g for the control diet group. Final body weight was significantly heavier (P < 0.05) in kelp group than in control group. However, the difference in the free glutamic acid levels in the muscles of the control and kelp group was minimal. These findings indicate that kelp can be used as an effective substitute for fish meal because it not only enhances growth but also reduces feeding costs.View full abstractDownload PDF (159K)
Program and Abstracts
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Takao Yoshimatsu2016 Volume 64 Issue 4 Pages 413-468
Published: December 20, 2016
Released on J-STAGE: December 20, 2017
JOURNAL FREE ACCESSDownload PDF (13494K)
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