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Volume 52, Issue 2
Displaying 1-13 of 13 articles from this issue
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Fumihiko ABE, Daijiro EDAGAWA, Seiji KIKUCHI, Hirokazu MARUTA, Kosaku ...2004 Volume 52 Issue 2 Pages 109-120
Published: June 20, 2004
Released on J-STAGE: December 10, 2010
JOURNAL FREE ACCESSWe conducted a study on several types of eelgrass-shaped substrates to examine its ability to serve as a substrate for the growth of algae and to attract marine animals. On 14th July 2000, seven 2×2 m iron lattices covered with eelgrass-shaped substrates were placed on the seabed at a depth of 7 m in Morode Cove in Misho Town, Ehime Prefecture. The eelgrass-shaped substrate (mariron) has six different configurations: green, long, and thick (Zone 1) ; green, short, and thick (Zone 2) ; white, short, and thin (Zone 3) ; green, short, and thin (Zones 4 and 6) ; green, long, and thin (Zone 5) ; green, long, and thick with an unplanted area in the middle (Zone 7) . There was a significant difference between the thin and thick units in the growth of algae, and more algae attached to the thin units. A quadrat was also placed in a natural Zostera japonica bed and on the sandy bottom. A census of the fishes was taken at every spring tide from July 2000 to July 2001. A total of 90 spp. in the 7 eelgrass-shaped substrate zones, 55 spp. in the natural Zostera bed area, and 22 spp. in the sandy bottom area were observed, and individuals were significantly more numerous in the first habitat than in any of the others. The greatest abundance of species and individuals inhabited Zone 1. Zone 2, where the smallest numbers of species and individuals were observed, was somewhat different from the other zones. Oval squid Sepioteuthis lessoniana lesson appeared in the experimental area in late-April 2001, and laid egg capsules mainly in the thin-type zones.View full abstractDownload PDF (4158K) -
Mitsuhiro NAKAYA, Tetsuya TAKATSU, Masayasu NAKAGAMI, Mikimasa JOH, To ...2004 Volume 52 Issue 2 Pages 121-128
Published: June 20, 2004
Released on J-STAGE: March 09, 2010
JOURNAL FREE ACCESSDuring the spring in the coastal waters of Hakodate Bay the shrimp Crangon uritai is the predominant predator on larval and juvenile marbled sole, Pleuronectes yokohamae. To investigate the prey preferences of C. uritai, P. yokohamae and two other prey species, a mysid Nipponomysis sp. and a gammarid Haustorioides japonicas, were used for predation experiments. Among the three prey organisms studied, Nipponomysis sp. was preyed on first, followed by P. yokohamae, and finally H. japonicas. Prey profitability did not differ between P. yokohamae and Nipponomysis sp., though H. japonicas was less profitable. Nipponomysis sp. was larger, more perceptible, and slower to escape than P. yokohamae. A relatively high abundance of mysid Nipponomysis sp. could restrict and reduce predation on P. yokohamae by C. uritai. Gammarid H, japonicas was able to escape relatively more easily, because its harder and slippery skin required more handling time than the other prey, possibly making it an undesirable food source for C. uritai. High perceptibility and low escape ability may be the most important factors affecting prey choice of C. uritai.View full abstractDownload PDF (1295K) -
Taichi KOYANO, Satoshi WADA2004 Volume 52 Issue 2 Pages 129-132
Published: June 20, 2004
Released on J-STAGE: March 09, 2010
JOURNAL FREE ACCESSEffect of fishery on density of S. luhuanus was surveyed with monthly change of density from April to December in 2002 and yearly change in catch for five years in Uranouchi Inlet, Tosa Bay, Japan. Monthly density in S. luhuanus did not show seasonal fluctuation with a peak in summer, which was reported in other populations. Although the highest density was recorded in May, it largely decreased in the following months, suggesting that the fishery activity for S. luhuanus might decrease the density of our study site in fishery area. However, the average catch amount per day did not change among years from 1998 to 2002. This suggests that introduced larva form other sites might contribute to stabilize the fishery population in Uranouchi Inlet.View full abstractDownload PDF (548K) -
Tadashi IMAI, Yoshimasa TOYOTA, Nobuhiko AKIYAMA2004 Volume 52 Issue 2 Pages 133-138
Published: June 20, 2004
Released on J-STAGE: March 09, 2010
JOURNAL FREE ACCESSThis study dealt with the relationship between the survival of Macrobrachium nipponense larvae and feeding frequencies with Artemia nauplii in freshwater rearing condition. The materials were taken so as to represent three different environmental conditions of original distribution areas, i.e. a freshwater lake, Lake Suwa-ko, a brackish water lake, Lake Sanaru-ko, and a river flowing into the sea, River Ohta-gawa. Artemia nauplii were given once, twice or four times per day to the larvae. The survival rates of the larvae taken from Lake Suwa-ko and Lake Sanaru-ko fed once or twice per day were 0% or 5%. The survival rates of the larvae improved 5% to 25% when fed four times per day. On the other hand, the larvae taken from River Ohta-gawa did not survive to next zoeal stage irrespective of the increased feeding frequency of Artemia nauplii. It is noticeable that in freshwater rearing, the increase of feeding frequency raised the survival rates of the larvae from two lakes, which are freshwater and brackish water, but did not affect that of the larvae from the river.View full abstractDownload PDF (785K) -
Shigeaki GORIE, Minoru TANDA2004 Volume 52 Issue 2 Pages 139-144
Published: June 20, 2004
Released on J-STAGE: March 09, 2010
JOURNAL FREE ACCESSThe growth and stomach contents of juvenile white-spotted conger Conger myriaster were studied in northeast Harima Nada, Seto Inland Sea, Japan. Leptocephalus larvae of the fish were collected from March to May in 2001 and juvenile fish were collected from April to September in 2001 and from May to August in 2003. Survey areas were 10-20 m depth and bottom sediment type was medium-fine sand and gravel. Mean total length of the juvenile fish changed from 80 mm in May to 190 mm in September. It is considered that leptocephalus larvae settled mostly in May, and the fish recruit to the fishery in the same year. As crustaceans and polychaetes were the main components in the stomach contents (accounting for 60-100%in terms of the numerical composition), we concluded that these are important feeding organisms for juvenile white-spotted conger. In the small length classes, crustaceans were the main food item. For larger length classes, there was a shift to polychaetes as the main food source. When the crustaceans were classified into lower taxa, the stomach contents shifted from amphipods to decapods with growth. In terms of the wet weight composition, this shift was observed at the total length of 130 mm.View full abstractDownload PDF (759K) -
Toshiya YAMAMOTO, Kentaro NOZAKI2004 Volume 52 Issue 2 Pages 145-152
Published: June 20, 2004
Released on J-STAGE: March 09, 2010
JOURNAL FREE ACCESSTo evaluate a reed zone as a nursery ground for fishes, temporal changes in the abundance of 8 groups of microcrustaceans were examined from April to July 1994 in shallower and deeper parts of a reed zone in Lake Biwa (Shiga Prefecture, Japan), and compared with the microcrustacean abundance recorded at the same reed zone in the 1960s. In the shallower part, total microcrustacean abundance ranged 188-3290 ind./l and had two peaks in late April and late May, whereas the lowest density was observed in June. Of the 8 groups, Bosmina longirostris, nauplii, Chydoridae, Podocopida and Scapholeberis kingi were dominant. Both the total abundance in the shallow and the deeper part in 1994 were significantly higher than in 1960s. Additionally, Podocopida and Harpacticoida were not collected in the 1960s. These large changes may reflect recent drastic alterations in the environment and bio-community in the littoral zone.View full abstractDownload PDF (1191K) -
Makoto FURUHASHI, Tetsuya UMINO, Takashi WATANABE, Heisuke NAKAGAWA, S ...2004 Volume 52 Issue 2 Pages 153-158
Published: June 20, 2004
Released on J-STAGE: March 09, 2010
JOURNAL FREE ACCESSAyu Plecoglossus altivelis were reared on four diets with protein levels of 45, 40, 35 and 30%, prepared by changing the amount of fishmeal. Growth, feed utilization, body composition and characteristics of the gut were investigated. Feed efficiency and protein efficiency ratio tended to decrease with reduction of dietary protein level, but there were no significant differences among the 45-35% protein diets. Biological parameters such as body length, body weight, condition factor and hepato-somatic index tended to decrease with protein level, and there were significant differences between the 45-35% and 30% protein levels, but the muscle ratio and intraperitoneal fat body ratio were the same among the experimental dietary groups. Furthermore, the diet protein level did not affect the chemical compositions of whole body and muscle. The characteristics of the pyloric caecum, such as number of columns, diameter, pleat height and pleat width, decreased with the protein level, and the lower the protein content in the diet, the higher the relative intestine length and pleat height. These findings demonstrate that the optimal level of dietary protein is 40% judging from the growth, although a dietary protein level of 35% did not significantly affect the growth of ayu.View full abstractDownload PDF (916K) -
Masato ENDO, Mayu SAITOU, Toshio TAKEUCHI2004 Volume 52 Issue 2 Pages 159-165
Published: June 20, 2004
Released on J-STAGE: March 09, 2010
JOURNAL FREE ACCESSThree feeding experiments were conducted to determine the optimum feeding level (OFL) and estimate the growth for larval and juvenile tilapia Oreochromis niloticus fed on Moina macrocopa at 28°C. In Experiment 1, live M. macrocopa were fed to O. niloticus, which had been separated into five different body weights (21.2 - 397.5 mg) under satiation 3 times per day. Satiation feeding level (SFL) of O. niloticus can be described by the equation: SFL (% fish body weight/day) =-0.565 × In (Body weight in mg) + 11.8. In Experiment 2, feeding trials with O. niloticus separated into three different body weights: 32.3, 72.6 and 189.7 mg were conducted under different feeding levels (33.3, 66.7 and 100% of the SFL) . Feed efficiency of O. niloticus was the highest in the upper feeding levels for each body weight class. The results indicated that the OFL is closely analogous to the SFL under the tested conditions. In Experiment 3, a continuous feeding trial with O. niloticus fry (9.7 mg body weight) at the SFL was performed in order to evaluate whether the body weight was suitable for the growth equation estimated from the results of experiment 1 for 4 weeks. A match was obtained between the estimated value and experimental result (X2-test, P>0.05) .View full abstractDownload PDF (1052K) -
Kazunori ARAYAMA, Hiroshi KOHNO2004 Volume 52 Issue 2 Pages 167-170
Published: June 20, 2004
Released on J-STAGE: March 09, 2010
JOURNAL FREE ACCESSVertical distributions of the Japanese whiting, Sillago japonica, larvae and juveniles and their main food organisms were examined in the sandy beach. A total of 319 Japanese whiting larvae and juveniles were collected from the bottom layer, but not collected in the surface. Their main food items such as pelagic copepods (mainly Acartidae, Paracalanidae, Oithona), polychaeta larvae and mysids were also distributed mainly in the bottom layer in daytime. These results suggest that the bottom layer is provides a suitable feeding place for the Japanese whiting larvae and juveniles, and the reason of these concentrated distributions is considered to be their body orientation in the bottom layer with weak water flow.View full abstractDownload PDF (575K) -
Satoshi KUSUDA, Nobuhisa KOIDE, Hiloshi KAWAMULA, Tetsuo TERANISHI, Et ...2004 Volume 52 Issue 2 Pages 171-175
Published: June 20, 2004
Released on J-STAGE: March 09, 2010
JOURNAL FREE ACCESSTo develop the cryopreservation diluent for spermatozoa of the endangered Sakhalin taimen, we examined the effect of the nature of cryoprotectants on post-thaw fertility. Fresh semen was diluted 4 times with each diluent, comprising 90% 300 mM glucose and 10% each cryoprotectant (dimethyl sulfoxide (DMSO), methanol, or glycerol) . The 100μl of diluted semen was dropped on dry ice to freeze and immersed in liquid nitrogen for over 2 h. Four pellets were thawed in 16 ml of a 120 mM NaHCO3 solution at 30°C. Egg batches of 20 g were immediately inseminated with thawed semen (Sperm to egg ratio was 5.0×106: 1) . Semen cryopreserved with methanol showed the highest fertilization rate (82.0±0.9%) among all the cryoprotectants examined. The fertilization rate of semen diluted with DMSO (45.1±2.2%) was significantly higher than that with glycerol (12.7±2.0%) . Semen cryopreserved with methanol yielded almost similar post thaw fertility to that of 50μl of fresh semen (78.4±2.4%) at the sperm to egg ratio of 2.5×106: 1. These results indicate that methanol is the suitable cryoprotectant for Sakhalin taimen spermatozoa.View full abstractDownload PDF (785K) -
Taiju SAITO, Katsutoshi ARAI, Etsuro YAMAHA2004 Volume 52 Issue 2 Pages 177-184
Published: June 20, 2004
Released on J-STAGE: March 09, 2010
JOURNAL FREE ACCESSThe embryonic development of shima-ukigori, Gymnogobius opperiens (Family; gobiidae) at 20°C was staged by morphological and histological criteria, and analyzed by cell-lineage tracing, with special reference to the embryonic patterning mechanism during pre-gastrula stage. Egg cytoplasm was separately distributed from yolk even in unfertilized egg, but included many yolk granules within it. The yolk granules were maintained until mid-somitogenesis stage, and disappeared thereafter. The third cleavage sometimes occurred horizontally. Yolk cell kept the spherical shape without yolk extension throughout the embryonic development. These properties are similar to those in gobiidae fish, but different from those in cyprinidae fish, such as zebrafish and goldfish. Cell-labeling at the 16- to 32-cell stage showed that the blastomeres mingled with each other during blastula to early gastrula stages, suggesting developmental fates are not destined in these stages. These results suggest that the fundamental mechanisms of embryonic patterning are conserved in varied fish species, although shapes of embryo and yolk cell are different.View full abstractDownload PDF (6319K) -
Kazuyo MATSUYAMA-SERISAWA, Satoru YAMAZAKI, Yukihiro KITADE, Yukihiko ...2004 Volume 52 Issue 2 Pages 185-198
Published: June 20, 2004
Released on J-STAGE: March 09, 2010
JOURNAL FREE ACCESSTracing of 15 systematic characters of Bangiales in which the genus Bangia and Porphyra are included was conducted based on a molecular phylogenetic tree constructed from small subunit (SSU) rRNA gene sequence data of 57 strains using ACCTRAN optimization. The SSU rRNA gene sequence data of Porphyra were determined in seven species including three unregistered species. In the phylogenetic tree, most strains diverged largely into three clades, one Bangia clade and two Bangia-Porphyra complex clades. This indicates that the genus Bangia and Porphyra are not monophyletic. In tracing, the evolution of gametophyte shape (systematic character of the genus) from cylindrical to leafy or leafy to cylindrical is considered to have occurred at least once or twice, respectively. The evolution of the cell layer in gametophytes (systematic character of the subgenus Diploderma) from monostromatic to distromatic is considered to have occurred once, but monostromatic strains appeared in two lineages. The evolution of chloroplast number per cell in gametophytes (systematic character of the subgenus Diplastidia) from monoplastid to diplastid is suggested to have occurred twice in different lineages. Although several assemblages were confirmed, strains with the same character status appeared in various lineages in terms of other systematic characters. Therefore, the systematic characters used in the present study were concluded not to reflect the SSU rRNA phylogeny. This is the first report on tracing systematic characters in Bangiales.View full abstractDownload PDF (2084K) -
Tsuneki AKIMOTO, Munenori HAYASHI, Mitsunobu IWABUCHI, Ken-ichi YAMAMO ...2004 Volume 52 Issue 2 Pages 199-200
Published: June 20, 2004
Released on J-STAGE: March 09, 2010
JOURNAL FREE ACCESSMedian lethal oxygen-saturation (LC50) in the pen shell Atrina (Servatrina) lischkeana increased from 4.9% to 9.8% for 48 hours and from 7.4% to 14.9% for 72 hours with the rise in the water temperature from 20.0°C to 27.5°C. However, all of these survived at 20.0°C for 24 hours and at 22.5 - 27.5°C for 12 hours in 0% oxygen saturation, and at 20.0 - 27.5°C for 3 days in 20% saturation. Based on the reaearch in the Ariake Sea, the mortality of the pen shell in the Ariake Sea was supposed not to be directly caused by hypoxia.View full abstractDownload PDF (239K)
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