Growth of Pacific saury Cololabis saira (Brevoort) inhabiting the western North Pacific wasstudied based on counting daily growth increments with a scanning electron microscope (SEM). The small-size group (knob length: 200-240mm), medium-size group (knob length: 240-280mm) and largesize group (knob length: >280mm) showed increments of 256±26.0 (S. D.), 405±76.1 and 566±48.2, respectively. Based on daily growth increment formation, we determined that the ages of the 3 groups were about 8, 13, and 19 months. Small- and large-size fish were considered tohave been hatched from autumn to winter, and medium-size fish from spring to summer. The oldest specimen of Pacific saury examined in this study was about 23 months of age; thus, the lifespan of Pacific saury in this area seems to be at least 1.5 years.

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Nitrogen flow in a chemostat culture of the rotifer Brachionus plicatilis was measured. It was found that a chemostat could keep the rotifer in a stable condition and were suitable for studying the effect of algal density. The rotifer egested 70-80% of the ingested nitrogen as particulate organic nitrogen (PON) and about 80% of the remaining assimilated nitrogen was utilized for reproduction. Low net growth efficiency (K₂) at high algal densities proved “superfluous feeding”. 20% of PON egested was incorporated in the rotifer again by bacteriovory, and 13% of that was remineralized to NH⁺₄ by bacteria. The PON was accumulated as a suspended or attached form in the culture vessel, which might cause an unstable environment. For a safety culture of the rotifer, removal of PON is an effective counter plan.

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The purpose of this study was to find a method of predicting the recruitment size of the ayu Plecoglossus altivelis population, using the data obtained in certain surveys before the main fishing season. In the ayu population of Lake Biwa it is known that the survival rate in the early life history depends on the population density. Adopting the population size at the beginning of February as therecruitment size, we theoretically derived a general relationship between the recruitment size and the mean number of juveniles caught by a net survey in December. We then calculated the recruitment size that satisfied the derived relation as closely as possible, using a cohort analysis. We found that the obtained relation can give a practical estimate of the recruitment size from the mean numberof juveniles caught in December.

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Six marine and four freshwater specimens of the bull shark Charcarhinus leucas were collected from different areas in Latin America and Australia, and subjected to analysis for mitochondrial DNA sequences in the cytochrome b gene and D-loop region.
The bull shark collected during our field survey contained two regions, D-loop and highly conserved cytochrome b region. There was no variation in the cytochrome b gene segment (405 bp) among seven specimens collected from the Atlantic Ocean and related river systems in Mexico and Nicaragua. However, there was one polymorphic site in the Australian shark compared with these sharks, while the 366th thymine was specific to Mexican marine sharks collected from the Pacific Ocean.
Analysis of the D-loop region (484 bp) revealed 17 polymorphic sites among all samples examined. In contrast to the cytochrome b gene, two sequence patterns having one gap and four variable sites were recognized in the D-loop region among seven specimens collected from the Atlantic sites. However, the Australian freshwater shark and Mexican marine specimens from the Pacific Ocean showed their respective area-specific sequence patterns as in the case of the cytochrome b gene.

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The fine structure of the alimentary canal epithelium in leptocephali of the Japanese eel Anguilla japonica (11.0-47.7mm in total length) was examined. The alimentary canal was histologically divided into three segments: fore-, mid-and hindgut. No size-dependent differences occurred in either morphological or cytological features of the epithelia in each segment. The foregut epithelium comprised flat cells, which lacked any absorptive function, unlike the mid- and hindgut. The midgut absorptive cells were characterized by numerous vacuoles and a highly developed lamellar membranous structure with large, closely associated mitochondria. The development of the lamellar membranous structure suggested that water and solute transport occurred actively in the midgut epithelium. In the hindgut absorptive cells many pinocytotic vacuoles with fine particle inclusions were present in the upper half of the cytoplasm, in addition to many macrophage-like cells distributed under and sometimes intruding into the hindgut epithelium, suggesting that the hindgut is involved in the uptake and intracellular digestion of intact macromolecules.

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Recruitment observation or estimation always includes uncertainties in some degree. The optimal escapement policy considering the uncertainty in recruitment observation is analyzed, assuming that the spawner-recruitment relationship is welldetected. When there is an observation error, the spawner varies from an expected value, by which the recruitment in the next year also varies though the spawnerrecruitment relationship is already determined by detailed research. In such cases, the criterion of the constant escapement strategy should be changed. The model predicts that the spawners should be increased with increasing magnitude of estimation error, by which fishery yield can be improved. And it is also suggested that although the yield is increased by strategy considering uncertainty in recruit estimation, it decreases with increasing observation error.

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The promotive and suppressive effects of coexistence of bacterial strains on the growth of a diatom Chaetoceros gracilis were investigated under laboratory conditions. Tested bacterial strains were isolated from the diatom mass culture tanks at a kuruma prawn farm. To evaluate the effect of each bacterial strain, the growth pattern was compared between cultures with and without bacterial medium addition.
In diatom growth with the coexistence of Flavobacterium sp. in the ASP6 medium, the diatom cell yield during a 16-day culture period and specific growth rate were high compared to axenic culture as a control, whereas the duration of lag time and the variation among daily cell densities from four replicate cultures were as small as those in the control. These facts indicate that this bacterium greatly promotes diatom growth. However, four tested strains had no apparent effect and seven strains had a suppressive effect.

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Sexually immature male eels (253g average body weight), reared in sea water at 20°C, were injected weekly (14 times in total) with human chorionic gonadotropin (HCG) at a concentration of 250 or 750 IU/fish/week. Changes of the milt weight and milt quality were examined two days after each injection. Some of the treated males of both the 250 IU and 750 IU groups spermiated after the 5th injection, and most males spermiated after the 6th injection. In the 250 IU group, the milt weight gradually increased with increase in the repetitions of injection. It became constant (1-2g) during the period of the 11th-13th injection, and reached 4.0g after the 14th injection. Acquisition of potential for sperm motility was attained during the period of the 7th-9th injections and the percent motility of spermatozoa at 15 sec after dilution with 450mM NaCl remained at approximately 70% until after the 14 th injection. Milt pH (8.1-8.2) during the period of the 7th-9th injection was significantly higher than the 10th-11th injection period. Serum 17, 20β-dihydroxy-4-pregnen-3-one levels in the males of both groups remained low (0.1-0.2 ng/ml) throughout the experiment, although they were significantly higher than the saline control levels (0.05-0.08 ng/ml). In the 750 IU group, there was a marked difference in milt weight between individual males. The mean total milt weight throughout the experiment per fish of the 250 IU group was 9.4g, and that of the 750 IU group was 6.1g. The results indicate that repeated weekly injections of HCG at 250 IU/fish (about 1 IU/gBW) over 10 weeks is efficient for the artificial maturation of immature male eels.

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The effect of Chattonella exposure on gill histology of yellowtail was examined to clarify the following questions: (1) Is the branchial edema, previously reported as the main branchial lesion in response to Chattonella exposure, truly caused by Chattonella cells or a secondary histological alteration by fatal hypoxemia during the exposure? (2) Is the branchial edema responsible for the rapid decline of blood oxygen levels during the early stages of Chattonella exposure? Fish dying from Chattonella exposure showed many types of lesions, especially severe epithelial separation in the lamellae and filaments. In contrast, the gills of fish dying from environmental hypoxia showed very few lesions and were histologically hardly discernible from the control gills. This demonstrated that the branchial edema was induced by Chattonella and not by hypoxemia. On the other hand, the epithelial separation had not developed when the tissues were sampled immediately after the onset of hypoxemia. Therefore, the edema cannot be the cause of hypoxemia. The only histological change observed in the gills sampled at blood oxygen drop was blockade of interfilamental spaces by mucus. Based on these results and the previous findings of oxygen radical production by Chattonella, we hypothesized that oxygen radicals, released from Chattonella cells, stimulated mucus cells in the gills, and the secreted mucus, possibly plus Chattonella cells trapped within the mucus, destroyed the gas exchange capacity of the gills by shunting respiratory water current away from the lamellae.

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A 6-week feeding experiment was conducted to evaluate the nutritional value of malt protein flour (MPF) as an alternative protein source for fish meal in the diets for fingerlingred sea bream Pagrus major. In the control diet, white fish meal (WFM) was used as the sole protein source to provide approximately 52% crude protein. In the test diets, 10 to 50% of the WFM protein in the control diet was isonitrogenously replaced by MPF. A diet containing defatted soybean meal (SBM) at 20% replacement level was also prepared. These diets were fed to satiation to the fish withan initial mean weight of 10g at 23°C.
The daily feed consumption rate decreased as the MPF level in the diets increased, whereas the consumption rate of the SBM diet was almost the same as that of the control diet. No difference was observed between the weight gains of the fish fed the control diet and the diets containing MPF at the 10 to 30% replacement levels or SBM. Furthermore, the highest feed efficiency and retentions of protein and energy were noted in the fish fed the diet with the 30% MPF level, and the lowest values in the fish fed the control and the SBM diets.
These findings suggest that MPF can substitute 30% of WFM protein with the most effective utilization of dietary protein.

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In order to elucidate the relation to in vivo lipid peroxidation and antioxidant defenses in cultured fish, in vivo lipid peroxidation levels and antioxidant activities in the liver and plasma of cultured yellowtail Seriola quinqueradiata obtained from Farm A and Farm B in Kagoshima Prefecture were compared with those of wild fish caught in the Yatsushiro Sea. The liver 2-thiobarbituric acid reactive substance (TBARS) values were significantly higher in Farm A fish and numerically higher in Farm B fish than in wild fish. Similarly the plasma TBARS values were significantly higher in Farm A fish and numerically higher in Farm B fish than in wild fish. The levels of α-tocopherol and ascorbic acid in the liver of Farm A fish were significantly lower than those of Farm B fish. This result may reflect the dietary levels of these vitamins. The levels of α-tocopherol and ascorbic acid in the liver of Farm A fish were also significantly lower than those of wild fish. Bilirubin was detected in the plasma of Farm A, suggesting an early stage of jaundice. Glutathione peroxidase activities in the liver and erythrocytes of cultured fish were significantly higher than those of wild fish. Superoxide dismutase activities in the liver of cultured fish were significantly higher than those of wild fish, but no difference was observed between the erythrocytes enzyme of cultured and wild fish. Aspartate and alanine aminotransferase activities in the plasma of cultured fish were significantly higher than those of wild fish. These results suggest that cultured fish may suffer from more oxidative stress than wild fish. Therefore, α-tocopherol and ascorbic acid supplements are necessary in the diets of yellowtail to prevent the progress of in vivo lipid peroxidation which may brings about many diseases.

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The effect of photooxidized methyl oleate on the carp myofibrillar ATPase activity and the crosslinking reaction of myosin heavy chains were investigated.
Upon addition of photooxidized methyl oleate, the myofibrillar Ca-ATPase activity changed biphasically; a gradual increase in the activity by the addition of a small amount was followed by a decrease in the activity by further addition. On the contrary, the K-ATPase activity simply decreased by the addition of photooxidized methyl oleate. Moreover, the photooxidized methyl oleate induced the cross-linking reaction of myosin heavy chains. Both the changes in ATPase activity and the increase of cross-linked myosin heavy chains were related to the content of peroxide present in photooxidized methyl oleate.
Hydroperoxides isolated from photooxidized methyl oleate by thin layer chromatoraphy decreased the K-ATPase activity and induced the cross-linking of myosin heavy chains. These changes in myofibrillar protein induced by hydroperoxides were very similar to those with autoxidized triglycerides.
Therefore, it was indicated that hydroperoxides produced during the autoxidation of lipids caused the ATPase activity change and cross-linking reaction of mvosin heavy chains.

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The stability of actomyosin from carp during ice storage was studied focusing onthe effect of disulfide bond formation on the protein conformational change. Behavior of characteristics of the protein in the presence of cryoprotectants and a reducing reagent during ice storagewas investigated by measuring SH content, Ca²⁺-ATPase activity and surface hydrophobicity, and by performing SDSPAGE.
In the case of no additives, a decrease in SH content and a dimer formation of myosin heavy chain (MHC) through SS bonding were observed along with a decrease in Ca²⁺-ATPase activity and an increase in surface hydrophobicity. The dimer formation of MHC proceeded even in the presence of cryoprotectants, although the Ca²⁺-ATPase activity was stabilized throughout ice storage. In addition, a slight change in surface hydrophobicity was also observed. On the other hand, the addition of a reducing reagent (dithiothreitol) showed that the decrease in Ca²⁺-ATPase activity and the increase in surface hydrophobicity occurred without the dimer formation of MHC through SS bonding.
Therefore, it was suggested that the oxidation of SH groups in myosin heavy chain and the MHC dimer formation by SS bonding proceed regardless of the conformational change of myosin head portion related to Ca²⁺-ATPase activity during ice storage.

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Sedimentation equilibrium and viscosity measurements were carried out on six agar samples in 0.1M KCl at 65°C. The sedimentation equilibrium data showed that the weight-average molecular weight, M_w, of these agar samples ranged from 3.0×10⁴ to 1.9×10⁵. The ratio of z-average molecular weight, M_z, to M^w, , which indicated the inhomogeneity of molecular weight, ranged from 1.1 to 2.9. The wide moleculare weight distribution suggested the cleavage of agar molecules during alkali treatment. Although the gelation point depended on molecular weight in the case of the same origin sample, the molecular weight dependence of gelation point did not exist in different algal species. From the log-log plots of intrinsic viscosity, [η], versus _??__w, it was clear that the data plots approximated the following equation: [η]=8.75×10^-4 M^0.68. From the magnitude of the exponent value, 0.68, we considered that agar molecules were in the form of random coils in0.1M KCl at 65°C. Furthermore, the molecular shape of agar in the case of adding an inhibitor of hydrogen bonding to the solution was also random coils, which supported the view that the sol-gel transition of agar is due to the formation of hydrogen bonds.

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Lipid class, fatty acid, and glyceryl ether composition in different tissues of the male and female arrow squids Loligo bleekeri was determined.
In both sexes of this species, the livers had a relatively high amount of lipids, which were characterized by high quantities of triglyceride class. On the contrary, the lesser lipids from the muscles and gonads were low in the above lipid class but high in phospholipids. The unsaponifiable matters isolated from the tissue lipids contained remarkably high levels of sterols and minor amounts of glyceryl ethers and alkenyl types. The component fatty acids of the muscle and/or liver lipids were very similar in composition between both sexes, respectively. Few differences were found in the percentage of the component fatty acids between the lipids from the testes and ovaries. While the fatty acid composition of the muscle lipids was markedly different from that of the liver lipids, the former tending to be more polyenoic with abundant 22:6n-3 acid. Glyceryl ethers of the male and female liver lipids showed similar components: the most predominant constituent was chimyl alcohol.

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The lipid class and fatty acid composition of brain and eyes of unpigmented and normally pigmented Japanese flounder (Paralichthys olivaceus), reared using live food, were analysed. The neural tissues of normally pigmented and unpigmented fish showed a similar lipid class composition. However normally pigmented individuals had a higher content of polyunsaturated fatty acids in the polar lipid fraction, specially arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid. Considering the importance of docosahexaenoic acid in the composition of neural tissues, as well as eicosapentaenoic, and arachidonic acids in eicosanoid production, a relationship among vision, neural transmission, and pigmentation is suggested.

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The contribution of transglutaminase (TGase) to the setting of the fish flesh pastes at various temperatures was investigated. The pastes of Alaska pollack, horse mackerel, Spanish mackerel, Pacific mackerel, and common carp were set at 20°-40°C. The paste showed the highest TGase activity at 25°-30°C and the lowest activity at 40°C. Addition of 5 mmol/(kg mince) EGTA nullified the activity of the pastes set at each temperature. The suwari gels formed with EGTA around 30°C from the former two fishes and were considerably lower in the breaking force than ones formed without EGTA at the same temperature from each fish. However, the gels formed with EGTA at 40° were not so different in that force from ones formed without it. The findings suggest that in the formation of protein network structure, non-covalent bonds play an important role at the setting around 40°C, but covalents bonds formed by the catalysis of TGase do at the setting around 30°C.

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In our continuing search for effective antifoulants from marine invertebrates which can be used as substitutes for effective but highly toxic agents such as organotin compounds, we found that the lipophilic fraction from the extract of a Palauan octocoral of Sinularia sp. inhibited settlement of the blue mussel Mytilus edulis. Bioassay-guided isolation afforded five polyhydroxylated sterols with or without a monoacetyl functional group such as 6β-acetoxy-24-methylenecholestane-3β, 5α-diol. The inhibitory activity of one of these compounds against the settlement of the blue mussel was found to be 34% of that of CuSO₄, a standard antifouling agent. The activity of all five compounds was approximately 2 to 5 times stronger than that of cholesterol, β-cholestanol and β-sitosterol, suggesting the importance of the hydroxyl and/or acetoxyl groups for antifouling activity.

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Milkfish was used as a raw material to establish and obtain fundamental data about the gelation of meat paste and inactivation of actomyosin Ca-ATPase by means of high pressure-treatment. Suwari, a setting phenomenon at low temperature, occurred at 50°C, while modori, a disintegrating phenomenon at high temperature, occurred at 60-70°C. The suwari temperature of meat paste treated at 3, 000 atm for 1h decreased from 50 to 30°C. Excellent gel was obtained after pressurizingat 1, 000, 3, 000, and 5, 000 atm for 1h and subsequently heating at 90°C for 10min. Heat-induced suwari was improved and modori was inhibited after pressuring at 3, 000 atm for 1h. The activity of Ca-ATPase was almost lost by treating at 3, 000 atm for 5min. Different patterns in Ca-ATPase inactivationwere observed when actomyosin was treated by pressurizing, heating after pressurizing, or pressurizing combined heating. Liability to denaturation of the protein indicated that pressure treatment was applicable to milkfish processing.

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We modified the conventional method for estimating a denaturation temperature ofcollagen, in which protease digestion and SDS-PAGE analysis are applied, in order to estimatedirectly a denaturation temperature of an insoluble collagen in a crude residual fraction after alkali (0.1 N NaOH) extraction (RS-AL) from muscular tissue. Thermal stability of the major collagen (TypeAR-Ia collagen) in the RS-AL from the kuruma prawn muscle was examined by the method. Intact Type AR-Ia collagen in the RS-AL had a denaturation temperature of 39.2_??_39.4°C in both neutral (20mM sodium phosphate, pH 7.2) and acidic conditions (0.1M acetic acid). On the other hand, the pepsin-solubilized Type AR-Ia collagen showed a denaturation temperature of 37.7°C in the neutral conditions, and 34.8°C in the acidic conditions. These facts indicate that the thermal stability of intact Type AR-Ia collagen is considerably reduced by the proteolytic removal of telopeptides which results in the change of its molecular characteristics, such as molecular arrangement or solubility, in neutral and acidic solvents.

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The surface SH content of carp actomyosin decreased in a similar way to the total SH content during ice storage, regardless of the presence of sorbitol, as well as the formation of myosin heavy chain (MHC) dimer, indicating that the surface SH groups in myosin molecules were responsible for the oxidation of actomyosin.
The Ca²⁺-ATPase activity of actomyosin stored in the presence or absence of sorbitol was enhanced by the NEM modification of SH groups. EDTA-ATPase activity was stable during the storage despite the presence of sorbitol. These results indicate that reactive SH, SH₁, in myosin head was not oxidized.
The increase of Mg²⁺ (EGTA)-ATPase activity suggests that SH_a on the tail portion of myosin participates in oxidation during storage, no matter whether sorbitol was added or not.
These findings suggest that SH_a on the myosin tail portion, not SH₁ on the myosin head portion, is responsible for the oxidation of MHC and the formation of its dimer.

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12-Hydroxyeicosatetraenoic acid and 15-hydroxyeicosatetraenoic acid were produced as major and minor monohydroxylated products in a microsome fraction, when [1-¹⁴C]arachidonic acid was incubated with the microsome or cytosol fraction prepared from frozen stored gill tissue of red sea bream Pagrus major. The endogenousproducts extracted from the microsome fraction of red sea bream gill were isolatedby high performance liquid chromatography and identified as 12-hydroxyeicosatetraenoic acid, 12-hydroxyeicosapentaenoic acid and 14-hydroxydocosahexaenoic acid by ultraviolet absorption spectrometry and gas chromatography-mass spectrometry.These data suggest that arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid are converted to their monohydroxy derivatives via the hydroperoxides bythe action of 12-lipoxygenase-like enzyme, which is distributed in the microsomesof red sea bream gill.

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Application of isoelectric focusing in thin-layer polyacrylamide gels (IEF/PAG) to the study of opine dehydrogenases in marine invertebrates was described.The optimized IEF/PAG and the following activity bands detection showed high resolution and good reproducibility.It was useful for the detection of multi-functional enzymes which metabolize two (or more) distinct opines, and for the analysis of multiple enzyme forms (allozymes and isoenzymes) in tissues of marine invertebrates.

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The fatty acid composition of glycerophospholipids extracted from certain brain lobes and optic nerves of rainbow trout, a cold freshwater fish, carp, a relatively warmer freshwater fish, and skipjack tuna, a relatively warm seawater fish, was investigated. The telencephalon, optic tectum and cerebellum of all species contained almost similar level of 22:6n-3 in glycerophospholipids, except for the carp telencephalon. Glycerophospholipids of rainbow trout tissues were relatively richer in total levels of monoenoic fatty chains, such as 18:1n-9, 24:1n-9, and 18:1 dimethylacetal, than those of carp and skipjack tuna. These results suggest that the level of 22:6n-3 in glycerophospholipids should be differentiated not by temperature adaptation but by physiological functions of the nervous tissues.

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To understand the roles of carotenoids as singlet oxygen quenchers in marine organisms, quenching activities of eight major carotenoids, astaxanthin, canthaxanthin, β-carotene, zeaxanthin, lutein, tunaxanthin, fucoxanthin and halocynthiaxanthin were examined according to the method using a thermodissociable endoperoxide of 1, 4-dimethylnaphthalene as a singlet oxygen generator. The second-order rate constant for the singlet oxygen quenching activity by each carotenoid was determined, suggesting that an increasing number of conjugated double bonds in carotenoid was proportional to greater quenching activity. The quenching activity of each carotenoid was found to be approximately 40 to 600 times greater than that of α-tocopherol. The potency of these carotenoids suggests that they may play a role in protecting marine organisms from active oxygen species.

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A mitogenic lectin in the skin mucus of the kingklip Genypterus capensis was purified by a combination of affinity adsorption on the glutaraldehyde-fixed rabbit erythrocyte ghosts and chromatofocusing on PBE 94 gels. The lectin was a glycoprotein having a molecular weight of 28-34 kDa which was composed with two homogenous subunit(13.7 kDa). The isoelectric point was 6.45. Kingklip lectin agglutinated rabbit and horse eryttirocytes but not human ABO erythrocytes. The hemagglutinating activity was calcium ion-dependent and was inhibited effectively by asialo-mucin Type I and also by simple sugars such as N-acetyl-D-glucosamine.The amino-terminal sequence of the kingklip lectin was identified as Ser-Met-Cys-Asn-Cys-Gly-Trp-Ser-Gln-Phe-Ala-His-Leu-Ala-Tyr-Leu-Leu-Arg-Ser-Lys-Ala-.

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