Juveniles of the abalone, Haliotis discus of 15 mm in shell length were fully fed on Eisenia bicyclis or Ecklonia cave for about 3 months (102 days) in various densities (340-920 juveniles / 0.48m²), and the number of survivors, shell length, and body weight were recorded. The rate of increase in shell length and in body weight was reduced with the increase in the population density, but survival rate remained constant. The biomass increased linearly up to the density of 660 juveniles / 0.48m² with some reduction in the rate of the increase in the highest density.

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The crawling speed of the gill piece of Crassostrea gigas and Atrina (Servatrina) pectinata was faster than that of Scapharca globosa ursuss. With increasing the water temperature from 10 to 43°C with each 3°C at intervals of 1 h, the crawling speed of the three species was also increased, and the speed in Crassostrea gigas, Scapharca globosa ursuss and Atrina (Servatrina) pectinata reached the maximum level at 37, 30 and 30°C, respectively. Crawling movement in Crassostrea gigas, Scapharca globosa ursuss and Atrina (Servatrina) pectinata was stopped at 43, 40 and 40°C, respectively. The crawling speed in Crassostrea gigas and Atrina (Servatrina) pectinata was same under hypoxic and normoxic conditions with 40% or more oxygen saturation but decreased when the saturation dropped below 40%.

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Inhibitory effect of tributyltin oxide (TBTO) on the development of the oyster, Crassostrea gigas larvae 24 h after fertilization was observed at the concentration of 1.8μg/l and EC₅₀ for the development to straight-hinge larvae for 24h was the concentration of 3.0 pg/l. Acute mortality occured in oyster of developmental stages exposed to TBTO was examined. The values of 24-h LC₅₀ for fertilized eggs and straight-hinge larvae were 7.0μg/l and 15.0μg/l, respectively, and the value of 48-h LC₅₀ for spat was 35.0μg/l. These results suggest that the earlier developmental stages of oyster are more sensitive to TBTO that acts as a poison. Bioconcentration values were approximately 1, 000, 1, 500 and 2, 300 for the exposure at the concentration of 2.83, 0.92 and 0.29 μg/l, respectively.

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Growth and survival rate of artificially-produced yellowfin porgy, Acanthopagrus latus larvae from the stage of first feeding until 7 days after hatching was investigated for their tolerance to temperature, light intensity, salinity and delayed initial feeding.
High growth rate of 0.069±0.050 mm/day (mean±S. D.) with survival rate of 73.83±7.26 % was obtained for the larvae fed at 3 days after hatching, reared at 23°C, under normal seawater salinity and light intensity. At this temperature, only 1.83±0.62 % of the starving larvae survived at 6 days after hatching with no increase in the total length. Rearing condition under the light intensity 0 to 30 lx reduced the mean total length and decreased in the survival rate. The larvae exposed to 100 % to 10 % of seawater did not show much difference in mean daily growth but the survival rate declined as the salinity decreased.

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Culture of primary cells derived from the kidney of red sea bream, Pagrus major, were carried out. Red sea bream kidney No.2 cell line (RSBK-2) was established after cloning by limiting dilution method on 70th passages. RSBK-2 cell line possessed the following characteristics, cell type is fibrillar, the chromosome number is 48 as the other cells of red sea bream, colony forming ratio is 6.8%, and doubling time is 2.5days. The cell line grew preferably at a culture temperature of 20 or 25°C, with in the pH range of 6.4 to 7.2 and in MEM medium containing 0.68 and 0.8 % NaCl. After forming monolayer in the flask the cells inhibited further growth. The cell line could be stored at-80°C in a freezer. The cell line was confirmed not to be contaminated by any bacteria, mycoplasma or virus. From the results, it is suggested that established RSBK-2 was a normal cell condition but not transforming cell.

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The present study was conducted to investigate the optimal supplement level of sterile mutant of Chlorophyta, Ulva sp. var. meal to the cultured Japanese flounder, Paralihthys olivaceus. Fingerlings, with initial body weight of 5 grams, were fed for 120 days with four kinds of experimental diets. Diet A, which consisted of commercial pellet without Ulva sp. meal as additive, was used as control. Diets B, C and D were supplemented with 2 %, 4 %, and 8 % of Ulva sp. meal, respectively. After feeding, the blood properties and proximate compositions of muscle and liver were determined.
The highest growth rate, feed efficiency rate and protein efficiency ratio were obtained in the fish fed the diet B with 2 % of Ulva sp. meal as additive, and beyond this level, all the parameters were depressed with the increasing of the Ulva sp. meal supplementing level. More than 4 % Ulva sp. meal delayed the growth.
Hemoglobin level, hematocrit value, mean corpuscular hemoglobin and serum protein level were significantly higher in group B than that in group A. The highest correlation coefficients were observed between red blood cell, hemoglobin level, hematocrit value, serum protein level, condition factor and hepatosomatic index in group B, and the secondary in group C.
The protein content of eye-side muscle in group B was slightly higher than that in group A, but the lipid level decreased with increasing Ulva sp. meal supplementing levels. Lipid content in liver was significantly higher in group B and C. From the results, the optimal level of Ulva sp. meal is likely to be about 2 % for diets of the Japanese flounder.

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Genetic divergence and variability in six Puntius spp. were electrophoretically assayed. Twenty-four loci from sixteen enzymes and protein were identified. Almost all the loci for each species were monomorphic. Only two loci, 6PGDH in P. schwanenfeldii and MDH-1 in P. tetrazona were polymorphic. In general, genetic variability of the species examined was very low. The genetic distance between pair of stocks, based on the twenty-four isozymes and protein loci, showed no genetic differentiation among subpopulations of the Puntius gonionotus from different locations. From the estimation of genetic distance and the dendrogram, the Puntius spp. can be divided into four groups, e. g., the big fishes group, the small fishes group, and two other groups originated in China and Indonesia.

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Artificial seed of abalone, Haliotis diversicolor diversicolor, was planted in Nakanogo, Hachijo Island, during 1982 to 1986, and recovered by capturing with fishing in one, two and three years after plantation, to investigate their growth, recovery and survival rate. The size of the planted seed was from 15.6 mm to 25.0 mm in average. The average shell lengths of recovered abalones at one, two and three years after plantation were 57.5-62.1, 65.8-72.1 and 73.6 mm, and body weights were estimated to be 26.7-32.4, 34.7-47.1 and 49.6 g, respectively. Growth increment was greater in smoller seed than larger ones. There was significant negative correlation (P < 0.01) between growh increment and planting size, ranging from 10 to 30 mm. The accumulative recovery rates ranged from 2.2 to 23.6 % until two to three years after plantation. The survival rates after one year of plantation ranged from 11.8 to 58.5 %, which were calculated from recovery number and catching rate estimated by DeLury's method.

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“Luteinizing hormone releasing hormone analogue” (LHRH-a) from cholesterol-pellet implants has been found to be released gradually and continuously inside the fish. The effects of LHRH-a on the maturation and spawning of red sea bream, yellow tail, and Japanese founder have been extensively studied. However, the effect of LHRH-a on the egg hatching rate has not been reported.
The present experiment was carried out to investigate the overall effects of LHRH-a on maturation, spawning and hatching rates in red sea bream, Pagrus major by controlling temperature and photoperiod.
The experiment was conducted from January 27 to April 8, 1993, and consists of three treatment groups: A, B, and C. Experiments with groups A and B were done in 10 m³ and 30 m³ concrete tanks, respectively, and both of the brood stocks received Group A, however, temperature was maintained around 17 °C and photoperiod was controlled to 16L: 8D, whereas Group B was reared under natural condition, i. e. without controlling light and temperature. Group C was “control” group without hormone implantation in a fish pen (5×5×5m) in the sea.
Amounts of LHRH-a implanted ranged from 100 to 150 μg/ind. At every 10 days after the hormone implantation, the gonadosomatic index (GSI) was determined. The spawning dates and hatching rates were also recorded.
First spawning occurred on February 4 in Group A, February 11 in Group B, and March 17 in Group C. The hatching rates in Group A, B, and C were 23.2, 0, and 68.4 %, respectively. The spawning occurred when the GSI in fish ranged from 4.4 to 5.7. The highest GSI, 15.4 was observed on February 25 in Group B, but, it was considered as over-maturation.

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A small survey and rearing experiment were carried out to clarify the effect of culture methods on the growth of bay scallop, Pecten albicans at Oki Island and Shimane peninsula, Shimane prefecture. The elongation of the shell length was influenced by the degree of current speeds, while the growth of soft parts was not influenced. The growth rate in culture cages with a long line system was higher on the use of lantern net and bottom settling net than on that of the other nets. These differences could be explained in terms of differences in stabilizing the cages and the area per individual in cage.

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A total of 1138 specimens of 27 potential predatory fish species of hatchery-raised Japanese flounder fry were caught around the nursery ground until 37 days after the release of flounder fry. Flounder fry were found in stomachs of 5 species, larger Japanese flounder, greenling, Hexagrammos otakii, skate, Raja porosa, rock fish, Sebastes schlegeli, and barfin flounder, Verasper moseri. The former two species were confirmed as the most significant predator of the released flounder fry. Predation rates of predatory fishes on the fry were high, 12 to 30 % during about 1 week after release, fluctuated from 0 to 13 % in the second week and Predation was found until the 28th day after release. Total length ratio of predator/prey was 3.2-5.1 for canibalism and 2.8-7.8 for the greenling. Considering the predator-prey size relationship and size distribution of predatory fishes in the field, the best release size were estimated about 10 cm TL for effective avoidance of predation.

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Long-term observation on areas where algal germlings settle is necessary in order to define the mechanisms of algal attachment. In this study, germlings of Myagropsis myagroides that had settled on epoxy resin were cultured for 2 months at 20°C and 3, 000-4, 000 lx (12 L/12 D) . Small pieces of the resin bearing the germlings were embedded in Spurr's resin, and then sections of the settlement area were observed by light microscopy. Features of germling growth such as the length of the thallus, stem, longest leaf, and longest rhizoid on the epoxy resin were not significantly different from those on glass slides during the culture period. After 2 months, all germlings on the glass slides detached from the substratum, whereas those on the epoxy resin continued to settle. These results clearly indicate that germlings of M. myagroides grow normally on epoxy resin for a long period and that the area of germling settlement can be observed using the present method. This approach may be useful for long-term observation of the mechanisms of algal attachment.

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Acute toxicity of organophosphate “MEP” [0, 0-dimethyl 0- (3-methyl-4-nitrophenyl) phosphorothioate] and carbamate “NAC” [1-naphtyl-N-methylcarbamate] to 11 species of aquatic organisms were determined by flow through condition bioassay.
Acute toxicity of MEP to kuruma prawn, Penaeus japonicas was extremely high, followed by red sea bream, pagrus major, yellowtail, Seriola quinqueradiata and mullet, Mugil cephaluswith comparatively high sensitivity. Common goby, Acanthogobius f lavimanusand ayu, Plecoglossus altivelisshowed moderate sensitivity. On the other hand, eel, Anguilla japonica showed low sensitivity. Acute toxicity of NAC to kuruma prawn was very high, followed by yellowtail and common goby with comparatively high sensitivity. Red sea bream, japanese flounder, Paralichthys olivaceus, black sea bream, Acanthopagrus schlegeli, mullet and ayu showed moderate sensitivity. Eel showed low sensitivity similar to its susceptibility to MEP. Shortnecked clam, Tapes philippinarumand pearl oyster, Pinctada fucata, both shell fish, showed low sensitivity to either of the two pesticides. Apparent intoxication symptoms were observed in aquatic organisms exposed to MEP and NAC. Hypersensitivity to stimulus, wild excitement and decrease in spontaneous motor activity were observed in kuruma prawn. In addition, change of body color, loss of equilibrium, swimming near the water surface, insensitivity to stimulus, convulsion and deformity of vertebra were observed in many fish. These intoxication symptoms were induced by the neurotoxicity of pesticides.

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A faunal and distributional survey of decapod crustaceans inhabiting the Yumesaki River system was carried out from 1990 to 1991. Sampling stations totalled 104. Seven species of Macrura and seven of Brachyura were collected. Neocaridina denticulata was found in almost every part of the river except the furthest points both upstream and downstream. This species is commonly found along this river. This is a typical feature of rivers which flow into the Seto Inland Sea. From a macrohabitat point of view Neocaridina denticulata could be said to be the most common and predominant species. The predominance of this species is attributed to both its flexibility of ecological niche and lack of competition with other species.

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The body length frequency distribution by sampling stations revealed that the large specimens of Neocaridina denticulata were found right under the Sugo dam, in the upper part of the Yumesaki River, and its branches in all seasons. Two possibilities can be proposed for the reason why the large specimens were found in the upper streams. One is, as generally suggested, that this species prefers remaining in its original habitat to migrating. Lower water temperature, fewer predators, and lack of competition with other species might be advantageous to the survivorship and growth of this species in the upper stream. The other is the possibility of Neocaridina denticulata, alandlocked species, to migrate both upstream and downstream.

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Concentrations of glycolytic intermediates and nucleotides were determined in young yellowtail, Seriola quinqueradiata fed with diets high in protein, lipid and carbohydrate, followed by 7 days starvation. Effects of physiological concentrations of ATP and F6P on the activity of hepatic phosphofructokinase (PFK) was also investigated. The concentration of ATP, ADP and AMP in the liver of the fish under feeding condition was around 1 mM each and that of G1P, G6P, F6P and FDP ranged from 0.1 to 0.5 mM, corresponding to the Km values for some glycolytic enzymes such as PFK. Dietary composition did not much affect the concentrations of glycolytic intermediates and nucleotides in the liver, while starvation decreased markedly the intermediates and slightly ATP. In vitro PFK activity was influenced markedly by the physiological concentration range of ATP and F6P. The results suggest that in vivo glycolytic activity was regulated effectively and reasonably by not only the enzyme levels but also by the concentrations of glycolytic intermediates and nucleotides as its substrate and effector.

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Water pollution by excess nutrients from coastal fish farms has become a serious problem. In order to reduce such eutrophication in the sea, an attempt to culture the sterile Ulva sp. was conducted in fish farms of Nagashima, Kagoshima Prefecture. The Ulva sp. used in this experiment was transferred from the Nagasaki Fisheries Experimental Station to our laboratory in 1987. Eighteen crab-traps were employed as culture cages of the Ulva sp. Stocking density was 8 g per cage. The cages were placed in a yellowtail farm at a depth of about 50 cm. The growth of the Ulva sp. and water temperature were observed every neap tide from September 1989 to September 1991. The average daily growth rate (DGR) of Ulva sp. was 21.7 % throughout the period. The higher DGRs, 23-30 %, were observed at higher temperatures of 25-28°C. On the contrary, the lower DGRs, 6-21 %, were obtained at lower temperatures of 13-15°C. Seasonal variation in growth was closely related to the variation in water temperature. The study suggested that the sterile Ulva sp. is a suitable aquatic plant for introducing a polyculture of seaweed and fish in the sea.

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The effects of Prefreezing conditions on the survival of conchocelis cells of Porphyra yezoensisform. narawaensis were investigated. Conchocelis cells were treated with a cryoprotective solution containing dimethyl sulfoxide (DMSO) and sorbitol, cooled slowly and plunged into liquid nitrogen. The survival after freeze-thaw cycle was examined by staining with neutral red.
The survival of conchocelis cells was the highest at the DMSO concentration of 1.50 M, at the sorbitol concentration of 0.50-0.75 M, at the pH of 8.0 and at the prefreezing temperature of -40--50 °C. Cooling rates of 0.5 °C /min and 1 °C /min gave better results for the survival than the rate of 2 °C /min.

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Fertilized eggs of three dragonet species, Repomucenus richardsonii, R. valenciennei and R. beniteguri, were obtained from spawners reared in a tank, and after hatching, the larvae were raised to the juvenile stage. Larvae were fed successively with selected S-type rotifers, unfiltered S-type rotifers, Artemia and minced krill for 40 days. The survival rate and average total length 40 days after hatching were 17.5 % and 22.8 mm for R. richardsonii, 21.3 % and 20.5 mm for R. valenciennei, and 2.6 % and 16.6 mm for R. beniteguri. The maximum size of prey edible by the dragonet larvae that had just started feeding was calculated to be 145 μm. It is expected that a higher survival of the dragonet larvae could be achieved by increasing the amount of rotifers smaller than 145μm.

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Defatted soybean meal (SBM) was purified by precipitation with phosphoric acid (soy protein concentrate 1, SPC1) followed by washing with hot water (SPC2) . The nutritive value and availability of SBM, SPC1 and SPC2 were evaluated by chemical analysis and by feeding fingerling yellowtail, Seriola quinqueradiata with diets containing 30 and 40 % SBM and SPCs for 30 days. The purification treatments remarkably increased the protein content while decreased the digestible carbohydrate content and trypsin inhibitor activity. There were no marked differences in the growth, feed conversion and proximate composition of the fish fed with diets containing 30 % of SBM and SPCs. In case of 40 % inclusion diets, the dietary inclusion of SBM exhibited the lowest growth and feed performance, while that of both the SPCs considerably elevated several serum components such as protein and phosphorus, and it also improved fairly the growth rate, feed conversion and nutrient retention, showing a performance comparable to the 30 % inclusion diets. These results have indicated that such a simple purification can improve the nutritive value and availability of SBM for yellowtail, and it can allow to elevate the inclusion amount of SBM in diets for the fish.

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