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Volume 62, Issue 3
Displaying 1-12 of 12 articles from this issue
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Original Papers
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Takashi Kikkawa, Makoto Nishimura2014 Volume 62 Issue 3 Pages 229-234
Published: September 20, 2014
Released on J-STAGE: September 20, 2015
JOURNAL FREE ACCESSIn Japan, red seabream Pagrus major larvae have been recommended as a saltwater test fish for acute toxicity test of chemicals. However, for this species, there is no reference data of the lethality of hexavalent chromium, which is recommended as the standard substance for ecotoxicological tests in some test guidelines. Therefore, we examined the acute toxicity of hexavalent chromium (as potassium dichromate) on larvae of P. major according to the test guideline of the Ministry of Environment of Japan. The median lethal concentrations obtained from duplicate treatments were 28 mg/l for 24 hours, and 17 mg/l for 48 hours (calculated as the concentration of hexavalent chromium). Compared to other saltwater species, P. major larvae showed higher susceptibility to hexavalent chromium.View full abstractDownload PDF (345K) -
Yoichi Minami, Michiyasu Yoshikuni2014 Volume 62 Issue 3 Pages 235-242
Published: September 20, 2014
Released on J-STAGE: September 20, 2015
JOURNAL FREE ACCESSThe sea cucumber Holothuria scabra is widely distributed in narrow waters in the tropical and subtropical Indo-Pacific and is an economically important species. The reproductive biology of this species around Shioya Fishing Port, Okinawa Prefecture was investigated from September 2010 to September 2011. Maturity was evaluated monthly in both sexes using the gonad-somatic index, and oocyte size and the histological features of the ovaries were also examined in females. We concluded from annual transitions in these indicators that H. scabra spawned primarily between May and October in 2011, and that individuals smaller than 600 g in body weight were sexually immature.View full abstractDownload PDF (854K) -
Hideki Hamaoka, Hiroshi Miyazaki, Tetsuya Nanko, Taiga Akamatsu, Junya ...2014 Volume 62 Issue 3 Pages 243-251
Published: September 20, 2014
Released on J-STAGE: September 20, 2015
JOURNAL FREE ACCESSTo identify spatial variations in the feeding habits of Trichiurus japonicus in the western Seto Inland Sea, Japan, we examined the carbon and nitrogen stable isotope ratios and the stomach contents of 256 specimens collected from four different sea areas. Stomach content analysis showed that the feeding habits of T. japonicus differed among sea areas, which may have been caused by spatial and temporal bias in the stomach contents. Additionally, trophic levels based on stable isotope analysis and the expected trophic niche by stomach content analysis did not agree. Greater sampling effort is needed to understand the feeding habits of fish considering spatio-temporal variations in the stomach contents of specimens. Using stable isotope analysis, we detected variations in the efficiencies of benthic and pelagic trophic carbon pathways, which were not detected by stomach content analysis, among sea areas. This result coincides with that of a previous study for primary production structure in the western Seto Inland Sea. Stable isotope analysis helps us effectively understand the feeding habits of fish with fewer efforts. These results will probably be useful in understanding the feeding ecology of T. japonicus.View full abstractDownload PDF (261K) -
Kouta Miyamoto, Tomoyuki Nakamura2014 Volume 62 Issue 3 Pages 253-258
Published: September 20, 2014
Released on J-STAGE: September 20, 2015
JOURNAL FREE ACCESSThe effects of shaded rearing and automatic feeding in juvenile masu salmon were examined to develop rearing techniques that produces fish which are more difficult to catch by angling. For one month, one hundred fish were placed in each of 4 different rearing tanks; 1, in a shaded tank with an automatic feeder; 2, in a shaded tank where the fish were hand fed; 3, in an open tank with an automatic feeder and 4, in an open tank where the fish were hand fed. The reared fish were moved to a concrete pond, and a one day angling trial (100 casts with bait) was conducted for each rearing group. The number of fish which were caught and fish which were not caught but that took the bait into their mouth was significantly less in the fish reared in the shaded tanks. No significant difference was observed between the fish, fed by hand and the automatic feeder. These results show that the fish reared in shaded tanks are more difficult to catch than fish reared in open tanks.View full abstractDownload PDF (439K) -
Hiroshi Hashimoto, Tomohiro Hayashi, Katsuyuki Hamasaki, Isao Kai, Hir ...2014 Volume 62 Issue 3 Pages 259-271
Published: September 20, 2014
Released on J-STAGE: September 20, 2015
JOURNAL FREE ACCESSTo elucidate the impact of aggressive behavior and cannibalism on mortality in mass-cultured larvae and juveniles of the greater amberjack Seriola dumerili, we clarified the relationship between predator-prey body size and fish growth, mortality and aggressive behavior. Aggressive behavior increased from 18 to 19 days post hatching and was positively associated with an increase in fish mortality. The size of cannibalistic fish was inferred based on the body height of prey fish and the mouth-size of predatory fish, as well as measurements of the total lengths of predatory fish and prey fish collected from mass-culture tanks. Body-size ratios of prey fish to predatory fish among fish exhibiting aggressive behavior, having partially swallowed prey (cannibals occasionally suffocated due to an inability to swallow prey), or having swallowed prey whole, were approximately ≤0.75, ≤0.63 and ≤0.35, respectively. Variations in the body size of fish reared in the same mass-culture tanks may elicit aggressive behavior in the larger juvenile fish, resulting in mass mortality of the smaller fish.View full abstractDownload PDF (1484K) -
Masashi Kaita2014 Volume 62 Issue 3 Pages 273-278
Published: September 20, 2014
Released on J-STAGE: September 20, 2015
JOURNAL FREE ACCESSTo better understand the pharyngeal tooth formation of devil stinger Inimicus japonicus, a histological examination was performed. This examination revealed that the odontogenesis of the I. japonicus is similar to the general formation of teeth in vertebrates. Functioning teeth appeared on the upper and lower pharyngeals Stage C (posthatching 8-days) and Stage E (posthatching 14-days), respectively. Pharyngeal teeth formed before the fish’s transition into the benthic zone. During this transition, the upper pharyngeal teeth were observed to be forming at both ends on the outside of the upper region, the lower pharyngeal teeth. Both the upper and lower pharyngeal teeth were connected to a non-pairing hinged attachment. It is thought that the teeth further allow I. japonicus to retain food effectively in the benthic zone.View full abstractDownload PDF (1163K) -
Kyosei Noro, Yasunori Sakurai2014 Volume 62 Issue 3 Pages 279-287
Published: September 20, 2014
Released on J-STAGE: September 20, 2015
JOURNAL FREE ACCESSThe sexual maturation and reproductive cycle of the north Pacific giant octopus Enteroctopus dofleini were investigated by regular sampling during the period from November 1989 to May 1997, in the adjacent waters of Tsugaru Strait. A total of 1,113 animals was sampled: 598 males, 515 females. Maturation stages of the animals were classified by the existence and length of spermatophores in males, and the coloration of the ovary in females. Immature specimens of both sexes were taken throughout the year. Maturing male specimens were present from March to December, mature male octopuses appeared between November and May. The minimum size of mature males was 9.8 kg in the mature season, becoming larger from March onwards. Female mature specimens were present from December to May. The minimum mature size in females was 8.5 kg in the mature season, and from January onwards they were almost the same size. The minimum size of copulated females was 10.6 kg in the copulating season (November to April), and from January onwards almost the same size. There were 23 copulated females among 65 mature females (35%).View full abstractDownload PDF (936K) -
Katsutoshi Kawabe, Hiroshi Kohno2014 Volume 62 Issue 3 Pages 289-294
Published: September 20, 2014
Released on J-STAGE: September 20, 2015
JOURNAL FREE ACCESSThis experiment was conducted to determine the suitable feeding frequency and stocking density during intermediate culture of young blacktip grouper Epinephelus fasciatus. Fish of 5.60 cm in average total length (TL) were fed to satiation with different feeding frequencies (1, 2, 3, 4 and 5 times per day or once every two days) for 33 days. No significant differences in survival rate were found among the groups. Feedings twice or more per day resulted in a higher daily growth rate. Fish of 8.94 cm in average TL were fed 1, 2 and 3 times daily or once every 2, 3 and 4 days for 38 days. One or more feedings per day resulted in higher survival and daily growth rates. In both experiments, feed conversion efficiency decreased with feeding frequency. Fish of 5.76 cm in average TL were reared at stocking densities of 100, 200, 400, 800, 1600 and 3200 fish per kl for 91 days. No significant differences were observed in daily growth rates. Survival rate at 3200 fish per kl was significantly lower than at 800 and 1600 fish per kl. Feed conversion efficiency was lowest at 100 fish per kl compared to all other densities.View full abstractDownload PDF (328K) -
Katsuyoshi Suitoh, Takuji Okumura, Fumihiro Yamane, Asatarou Tsuge, Yu ...2014 Volume 62 Issue 3 Pages 295-305
Published: September 20, 2014
Released on J-STAGE: September 20, 2015
JOURNAL FREE ACCESSThe kuruma prawn Marsupenaeus japonicus is an important species for fisheries and aquaculture in Japan, but details of its reproductive cycle in the western part of Enshu-nada, one of its most important habitats in Japan, have not been clarified. In the present study, we collected specimens of female M. japonicus during September-March and observed their ovaries histologically. Most female prawns had vitellogenic ovaries and some had pre-spawning or spent ovaries in September and October. In November, most female prawns had non-vitellogenic or regressing ovaries and the rate of vitellogenic female prawns decreased. In December and January, most female prawns had undeveloped non-vitellogenic ovaries. In February, some female prawns started to develop their ovaries and a few females had pre-spawning ovaries. In March, some females had spent ovaries. Furthermore, in February-March, body length and gonadosomatic index showed a significant positive correlation and larger female prawns had more developed ovaries than smaller ones. These results indicate that the spawning season of female M. japonicus starts in March and terminates in November in western Enshu-nada and that larger female prawns start ovarian maturation earlier than smaller ones.View full abstractDownload PDF (1052K) -
Tsutomu Tomoda, Shigeki Dan2014 Volume 62 Issue 3 Pages 307-318
Published: September 20, 2014
Released on J-STAGE: September 20, 2015
JOURNAL FREE ACCESSWe evaluated the efficacy of stagnant water larviculture for Pacific cod Gadus macrocephalus, using the rotifer Brachionus plicatilis acclimated at low temperature (12°C). Rotifer culture, nutritional enrichment, and larval rearing were performed simultaneously in a 50 kl larviculture tank, following the hottoke-shiiku method. Rotifer density increased slowly in the larviculture tank at 9.5-11.7°C. As a result, an initial double or triple inoculation of rotifers during the rearing period (28-30 days) was quantitatively sufficient. The amount of rotifers required for the production of 10,000 larvae (9 mm in total length) decreased substantially in the stagnant water system. We found no evidence of water pollution in either larviculture tank. Growth and survival of the larvae were similar to those reared by standard running water larviculture with daily feeding of rotifers. The n-3 highly unsaturated fatty acid (n-3 HUFA) content of rotifers in the rearing water was higher than in the secondary-cultured rotifers inoculated into the larviculture tank. We also observed a similar trend in the fatty acid composition of cod larvae. This rearing method appears to offer benefits including labor saving and improved nutrition.View full abstractDownload PDF (805K)
Short Papers
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Angel Guillén, Tomoki Honryo, Juan Ibarra, Amado Cano, Daniel ...2014 Volume 62 Issue 3 Pages 319-322
Published: September 20, 2014
Released on J-STAGE: September 20, 2015
JOURNAL FREE ACCESSEffect of water temperature on embryonic development of yellowfin tuna was investigated. Eggs were incubated at different water temperatures: 22, 24, 26°C (Experiment-1) and 28, 30, 32°C (Experiment-2). Developmental condition was observed and the elapsed time from the 2 or 4 cell stages until hatching was measured. Hatching occurred at 18.58 h for eggs incubated at 32°C. Eggs incubated at 22°C stopped development after the morula (late cleavage) stage. Experiment-3 was designed to examine the relationship between hatching time and the incubation temperature, and was expressed by two regression lines which intersected at 26.9°C.View full abstractDownload PDF (172K) -
Setuo Kiyomoto, Masanori Tagawa, Hiroaki Maeda, Shouichi Watanabe, Toy ...2014 Volume 62 Issue 3 Pages 323-325
Published: September 20, 2014
Released on J-STAGE: September 20, 2015
JOURNAL FREE ACCESSThe landing values (tonnage) of giant abalone Haliotis madaka are uncertain in most landing places, because they are treated in the same category with H. gigantea. We estimated their landing values from annual abalone landings and the record of shell lengths of the three abalone species by Ojika Town Office, in Ojika Islands, Nagasaki Prefecture. In 1998, the annual landed values of H. madaka were considered to be 1.2 mt, and the ratio to the total abalone landing was 7%. After 1998, the landed values have decreased year by year, and no specimens were landed after 2009.View full abstractDownload PDF (463K)
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