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Volume 59, Issue 2
Displaying 1-16 of 16 articles from this issue
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Originl Papers
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Toru Kobayashi, the Late Shozo Fushiki2011 Volume 59 Issue 2 Pages 191-198
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSWe used gynogenetic selection to stabilize genetically reproductive traits, namely, early spawning time and large egg size, in the Samegai breeding stock of rainbow trout (Oncorhynchus mykiss). We examined the distribution of reproductive characteristics, such as ovulation time and egg size, in a summer-spawning group, P, which matured by night-lighting in 1986. Large eggs were selected from females during the early, middle, and end stages of this spawning period and used to produce gynogenetic progeny. After the first gynogenetic generation, 1G, matured in the autumn of 1988, we compared their reproductive characteristics with those of P. Although the size of the 1G egg varied widely, their mean diameter was slightly larger than that of the Samegai stock. From P to 1G, the heritability of egg diameter was 0.164. The 1G progeny that inherited their maternal parent’s large egg size and early spawning time traits were called the early spawning and large egg strain. The second gynogenetic generation, 2G, which was produced from the eggs of this strain, started to ovulate 6 weeks earlier than the peak ovulation period of the Samegai stock. Our results suggested that gynogenetic selection may be faster and more effective than traditional selective breeding.View full abstractDownload PDF (236K) -
Ken-ichi Yamamoto, Takeshi Handa2011 Volume 59 Issue 2 Pages 199-202
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSOxygen uptake, ventilation volume and oxygen utilization in the Pacific oyster Crassostrea gigas were examined by measuring directly the ventilation volume and the oxygen partial pressure in the respiration chamber with the closed system at 20°C. The amount oxygen uptake and the oxygen utilization were calculated using the measured values of the ventilation volume and the oxygen partial pressure. The amount of oxygen uptake maintained almost the same level (0.25 ml/min/kg WW (wet weight of soft part)) until the oxygen partial pressure decreased to 24.9 mmHg. The ventilation volume and the oxygen utilization increased from 5.55 l/min/kg WW under normoxic condition to 8.89 l/min/kg WW (1.6 times that of normoxia)at 24.9 mmHg and from 0.8% under normoxic condition to 3.6% at 7.1 mmHg, respectively.View full abstractDownload PDF (233K) -
Ken-ichi Yamamoto, Takeshi Handa2011 Volume 59 Issue 2 Pages 203-206
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSChanges in the ventilation volume and the amount of oxygen uptake associated with feeding Chaetoceros gracilis were examined in the Pacific oyster Crassostrea gigas. At a densities of 20,000 cells/ml, the ventilation volume increased to 2.6 times (9.92 l/min/kg WW) that without feeding (1.92 l/min/kg WW). Similarly, the amount of oxygen uptake increased to 2.6 times (0.259 ml/min/kg WW) that without feeding (0.664 ml/min/kg WW). The ventilation volume reached a maximum at 27.3 minutes after the feeding, and the maximum level lasted for 8 hours or more.View full abstractDownload PDF (239K) -
Koji Kawana, Nakahiro Iwata, Takeshi Handa, Yoshihiko Baba, Kazumasa U ...2011 Volume 59 Issue 2 Pages 207-214
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSThe effects of smectite suspended in seawater on the blood properties of the Japanese flounder (Paralichthys olivaceus) were examined. The fish were exposed to smectite (0, 4.5, 10, 18 and 56 g/l) seawater solutions at 20°C. All the fish died within 4.5 h exposure to a 56 g/l smectite solution, and almost all fish within 24 h exposure to a 18 g/l smectite solution. Blood was collected from the dead fish soon after death and from the live fish after 24 h exposure, and was chemically analyzed. Hemoglobin and plasma protein concentrations did not vary significantly after exposure to the smectite solutions. Compared to the live fish and the control fish, the dead fish showed markedly high plasma lactate, blood total ammonia, and plasma electrolyte (Na+, Cl-, K+, Ca2+, Mg2+) concentrations and significantly low plasma glucose concentrations. Taken together, changes in the blood properties revealed that the lethal physiological disturbances were attributable to hypoxia caused by exposure to the high concentrations of smectite.View full abstractDownload PDF (163K) -
Tadakatsu Noro, Tadashi Takahashi, Yasushi Kuji, Seiji Goshima2011 Volume 59 Issue 2 Pages 215-223
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSMating seeds of the scallop Mizuhopecten yessoensis obtained from parents produced in natural spat collections on the coast of Iwate Prefecture and the Sea of Japan, Hokkaido, were bred separately and also hybridized. The spawning period was estimated based on the gonad somatic index and was earlier for scallops from parents produced on the coast of Iwate Prefecture than that for scallops from parents produced in the Sea of Japan, Hokkaido, and that for the hybridized seeds was intermediate. The spawning period was estimated by the attaching period for the natural spats collected on the coast of Iwate Prefecture. It was observed that, the spawning of early-attached seeds was earlier than that of late-attached seeds. Using allozyme genetic markers for 4 loci, a dendrogram constructed from genetic distances among natural seeds showed two distinct clusters comprising early-attached seeds and scallops from the Tohoku District, and late-attached seeds and scallops from Hokkaido, respectively. These results indicate that the spawning period is under genetic control, and that the differences in the spawning period among natural seeds are mainly due to genetic factors on the coast of Iwate Prefecture.View full abstractDownload PDF (526K) -
Makoto Taga, Yoh Yamashita2011 Volume 59 Issue 2 Pages 225-233
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSWe examined ontogenetic-appropriate changes of salinity for tiger puffer Takifugu rubripes and the associated originating mechanisms of growth difference. Larvae and juveniles at every 10-day post hatch (dph) interval from 10-70 dph were reared in 10, 20 or 30 ppt water conditions for 15 days. There were no significant differences in growth during larval period (<30 dph) among salinities; however, juveniles in low salinities (10 and 20) showed significantly faster growth than at 30ppt. We also measured feed intake, feed efficiency and oxygen consumption for 10-23, 31-43 and 50-63 dph fish under same salinity conditions. Larvae (10-23 dph) in low salinity conditions exhibited the largest oxygen consumption, but there was no difference among salinities for 31-43 or 50-63 dph juveniles. On the other hands, feed intake and feed efficiency were highest in 10 ppt for 50-63 dph juveniles. This study indicates that the appropriate salinity for growth of tiger puffer changes at approximately 30 dph and salinity-induced growth differences among fish are mainly caused by the energy available for growth increased by feed intake and feed efficiency at low salinities.View full abstractDownload PDF (523K) -
Yoshizumi Nakagawa, Takuya Hashimoto, Osamu Murata, Shigeru Miyashita2011 Volume 59 Issue 2 Pages 235-239
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSNaked-head large-eye bream Gymnocranius griseus larvae have small mouths, restricting their ability to feed on rotifers. In the present study, G. griseus were fed with trochophore larvae of the Pacific oyster Crassostrea gigas (50.2±2.4μm) as a primary food and their mouth size, i.e., mouth width (MW) and upper jaw length (UJL) were recorded daily. Mouth height (MH) of larvae was calculated by with a Shirota’s equation, MH=UJL0.5 at a mouth angle of 90o. At onset of feeding, three days after hatching (3 DAH), MH and MW were 216.8±13.6 and 227.2±16.8μm, and trochophore larvae were found in the digestive tract. Until 8 DAH, MW was significantly longer than UJL; thereafter, until 17 DAH (final day of measurements), MW and UJL were not significantly different. These results show the practical mouth height of G. griseus early stage larvae is smaller than the estimate given by Shirota’s equation; in consequence G. griseus larval prey capture ability is lower than expected compared with later stage larvae and early larvae of other fish species.View full abstractDownload PDF (172K) -
Tetsuya Tokuhara, Tomonori Kuwada, Tetsuji Kariya, Ryouji Fujii, Toru ...2011 Volume 59 Issue 2 Pages 241-245
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSFor the purpose of effective management of inland water fisheries cooperative associations, we examined the relationships between exploitation and awareness of anglers for stocking large sized masu salmon (Oncorhynchus masou masou) and amago salmon (O. m. ishikawae) and stocking efforts of fisheries cooperative associations. Results from creel censuses showed a bimodal distribution of angling exploitation indicating that anglers do not equivalently catch fish. Results from questionnaires showed no correlation between years of angling experience and awareness of anglers. Requirement abundance (37.2 fish/angler) calculated from awareness of anglers and the rate of angling exploitation exceeded maximum stocking abundance (20.2 fish /angler) by the fisheries cooperative association., Because we indicated the discrepancy between awareness of anglers and stocking efforts of the fisheries cooperative associations in this study, it is difficult to recommend the continuation of stocking large sized fish to gain satisfaction from anglers. However, supplemental rules such as special fees, bag limit and catch & release may improve the cost effectiveness of stocking large sized salmon.View full abstractDownload PDF (342K) -
Jing-Yu Li, Hikaru Endo, Yukio Agatsuma, Kazuya Taniguchi2011 Volume 59 Issue 2 Pages 247-253
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSWe examined the inhibitory effects of 2,4-dibromophenol (DBP) and 2,4,6-tribromophenol (TBP), which are released by the kelps Eisenia bicyclis and Ecklonia kurome, on survival and metamorphosis of larvae of the sea urchin Strongylocentrotus intermedius. Almost all larvae were fallen in the presence of 5 and 10 ppm, and died in the presence of 20 and 50 ppm DBP and TBP after 24 h, indicating that DBP and TBP have strong toxicity for the larvae of S. intermedius. The percentage of larvae that underwent metamorphosis in filtered seawater after 1 h of exposure to a one-half dilution of saturated dibromomethane solution (~60 ppm) as a chemical inducer reached 43% after 1 h and rose to 75% after 24 h. However, the percentage of metamorphosed larvae in filtered seawater containing 10 ppm DBP was reduced markedly to 25-34% within 24 h, and that in filtered seawater containing 10 ppm and 20 ppm TBP was reduced markedly to 24-34% and 4-10%, respectively, within 24 h. All larvae exposed to 20 ppm and 50 ppm DBP and to 50 ppm TBP died after 1 h. These findings suggest that DBP and TBP have a strong inhibitory effect on larval survival and metamorphosis for S. intermedius. These bromophenols may play a important role in the chemical defense of kelps against sea urchin recruitment in the field.View full abstractDownload PDF (157K) -
Shiro Nishihama, Tatsuya Yurimoto, Tsuyoshi Naito, Yuichiro Mori, Akih ...2011 Volume 59 Issue 2 Pages 255-264
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSWe investigated trends in the population density and shell length of the planktonic larva Ruditapes philippinarum in Ariake Bay, Japan. In 2004, larvae were abundant along the coast in October and November. The mode of shell length in October (180 to 189μm) indicated that the larvae had hatched out about 2 weeks previously. In contrast, in June 2005 the larvae were found mainly in the center of the bay and the shell length mode (140 to 149μm) indicated that 7 to 10 days had elapsed since the larvae had hatched. These distributions varied over different periods, and the larvae spread into areas where adults were absent, such as the central and inner parts of the bay. The temporal changes in the modes suggested that the adults spawned more than once in each season, or that the timing of spawning differed among populations within a season.View full abstractDownload PDF (863K) -
Naoyuki Suguro, Yasushi Aizawa, Kazumi Hosoya2011 Volume 59 Issue 2 Pages 265-273
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSThe propagation and rearing of Pseudobagrus tokiensis were performed in an ecological test pond from 2004 to 2007 in order to collect baseline data for habitat restoration and restocking purposes. Over the four-year period of the study, spawning in P. tokiensis occurred between the end of August and September. Pseudobagrus tokiensis exhibited sexual dimorphism with respect to growth with males tending to be larger. In females, maximum standard length (SL) was approx. 150 mm and individuals 120 mm< were rare, while males with SL exceeding 200 mm, were often observed. The relation between SL and the mass of both males and females, could be expressed by y=0.133x2.482 (R2=0.981) and y=0.0431x2.775 (R2=0.948), respectively, the logarithms of which were significantly different (t-test, P<0.001).
Successful propagation of the catfish during the study period resulted in a remarkable increase in their numbers in the test pond. They can, to a certain degree, inhabit artificial, concrete-lined streams, provided that a stable supply of spring water can be ensured, large natural stones are arranged along the side walls, and variously sized pebbles are used to line the stream bottom.View full abstractDownload PDF (1180K) -
Toyohiro Nishioka, Koh-ichiro Mori, Takuma Sugaya, Hiroyuki Takeuchi, ...2011 Volume 59 Issue 2 Pages 275-282
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSMortality occurred in juvenile red tilefish Branchiostegus japonicus reared at 16°C in a hatchery in 2004. The disease was characterized by abnormal swimming behavior and a vacuolating encephalopathy, and a betanodavirus (RGNNV), the causative agent of viral nervous necrosis (VNN), was isolated from the dead fish, proving that VNN accounts for the mortality. An epidemiological examination to determine the infection source of the virus was performed using the PCR-based method and revealed that wild red tilefish as broodstock were highly infected with the virus. This suggests that these broodstock are the most probable source of infection into the produced juveniles. For the prevention of VNN, PCR-negative broodstock were selected for artificial insemination, and the fertilized eggs were disinfected with electrolyzer-treated seawater and fish were reared in the treated water. As the result, RGNNV was not detected from produced larvae and juveniles by PCR and no VNN occurred during red tilefish seed productions from 2005 to 2009 in the hatchery, indicating that this procedure is useful to prevent the disease. This is the first report of an outbreak of VNN in red tilefish.View full abstractDownload PDF (386K) -
Viseth Hav, Ryo Ugawa, Yushiro Kinoshita, Fumihito Akishinonomiya, Ya ...2011 Volume 59 Issue 2 Pages 283-297
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSWe describe the morphological development of hatchery-reared Pangasius larnaudii using 150 larvae and juveniles 3.42 to 46.7 mm in body length (BL), sampled from day 0 to day 35. BLs of larvae and juveniles on day 0 were 3.53±0.1 mm (mean±SD), reaching 15.9±1.45 mm on day 15 and 39.4±4.03 mm on day 35. Notochord tip flexion began in the smallest larva of 3.42 mm BL, and a completely flexed notochord tip was evident in specimens of about 9 mm BL. Melanophores started appearing in larvae on such body regions as the eyes, ventral contour of the tail, dorsal surface of the gut, anal fin-fold, pectoral symphysis, lower jaw, maxillary barbel, antero-lateral part of the body, dorsal contour of the body and tail, caudal fin base, etc. There were individual variations among larvae as to the appearance of these melanophores, but all juveniles exhibited all of these melanophores. The juvenile stage started at 14.4 mm BL, at which point most of the body proportions relative to BL reached peak or constant values.View full abstractDownload PDF (1982K) -
Akihisa Sakai2011 Volume 59 Issue 2 Pages 299-306
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSThis study was conducted to examine the relationships among water temperature, plankton biomass, population density, and number of ascending individuals on the mean standard length (SL) of ayu caught in set nets in Lake Biwa from 1994 to 2010. The fluctuation trends of SL from February to May were similar, but the trends after June were different to before June. The difference of the size fluctuations between both periods suggests that large ayu ascend rivers after June. SL in February was negatively correlated with the density of larval ayu in the previous autumn. SL and the rate of increase in SL after March were positively correlated with the plankton biomass. SL in June and July was negatively correlated with CPUE of ayu in the set nets in April to June. These results indicate that the population density of ayu and plankton biomass affect the growth of ayu in Lake Biwa. SL of ayu in May can be forecast from the February values of SL, CPUE, and plankton biomass.View full abstractDownload PDF (475K) -
Tatsuya Unuma, Tadahide Kurokawa, Masaharu Tokuda, Kazuharu Nomura, Hi ...2011 Volume 59 Issue 2 Pages 307-313
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSThe individual rearing method using tissue culture microplates is useful for assessing fertility, hatchability, and larval survival in the Japanese eel Anguilla japonica. However, the rearing water needs to contain chemicals to suppress surface tension-related death that occurs upon hatching and antibiotics to prevent bacterial proliferation. To apply this method for assessing the occurrence of morphological deformities, it is essential to ensure that these additives do not induce malformations. Fertilized eggs were individually stocked in 48-well plates and reared until completion of yolk absorption. Polyethylene glycol 6,000 (PEG 6,000), bovine serum albumin (BSA), and an antibiotic solution containing penicillin G potassium (200,000 IU/ml) and streptomycin sulfate (0.2 g/ml) were added to the rearing water at various concentrations. PEG and BSA fully suppressed surface tension-related death at 1μg/ml and above without induction of dose-dependent malformations. The antibiotic solution fully prevented bacterial proliferation at 0.25μl/ml and above and did not induce dose-dependent malformations at 1μl/ml and below. However, it tended to increase the spinal curvature at 2.5μl/ml and above. We conclude that the individual rearing method can be applied to assess morphological deformities in eel larvae at the yolk absorption stage with minimum use of these additives within their effective concentrations.View full abstractDownload PDF (386K)
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Tomoyuki Nakamura2011 Volume 59 Issue 2 Pages 315-325
Published: June 20, 2011
Released on J-STAGE: October 08, 2012
JOURNAL FREE ACCESSIn order to contribute to effective stock and fishery management of masu salmon Oncorhynchus masou masou in Japanese rivers, regulations used to manage inland commercial fisheries and recreational fishing in the northwestern district of the Honshu Island, Japan were surveyed. The closed season, prohibited area, length limit and restrictions on fishing gears and methods were provided in the prefectural regulations for inland water fishery coordination and the regulations for recreational fishing of fishery cooperatives. There were some cases that bag limits and limited entry were used to regulate recreational fishing. Terms of the closed season, numbers and length of prohibited areas, kinds of restricted gears and methods, ranges of bag limits and limited entry varied between prefectural regulations and also those of fishery cooperatives. Fishing fees were used in the regulations of fishery cooperatives and the fees varied between cooperatives. Also, the fishing fees varied for adult (sakuramasu) and juvenile (yamame) salmon. It is important for the enhancement and conservation of masu salmon in rivers that the regulations imposed by prefectures and fishery cooperatives provide efficient restrictions and limits based on the condition of the salmon stock, habitat environment and opinions of fishermen and anglers.View full abstractDownload PDF (469K)
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