The cultured oyster biomass was estimated using biomass model, which was composed of the variables of growth, mortality, oyster fresh meat weight (FMW) and oyster numbers. Oyster growth and mortality were estimated using multiple linear equations composed of water quality variables. Results of the present study showed that actual growth was best modeled using an equation composed of difference values between two successive months of chlorophyll a, salinity and dissolved oxygen. The cumulative mortality estimated by the equation, which was composed of the variables FMW, annual minimum values of temperature, DO and chlorophyll a, also well simulated the observed mortality. The cultured biomass of oysters in different oyster culture areas (Atada, Miyajima, Hiroshima and Ondo) were estimated according to the culture techniques (Ikistu, Yokusei and Nokoshi). The results showed that the cultured biomass in all areas increased up to the maximum at the beginning of harvest season, and dropped sharply due to harvesting. The estimated growth and cumulative mortality of oyster were not much different between areas, indicating that a difference of oyster biomass in each culture area was significantly depended on the number of cultured oysters. Thus, this approach provides quantitative information of the cultured biomass of oysters in Hiroshima Bay which has been difficult to monitor directly in the culture area.

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Yellowtail Seriola quinqueradiata were fed on extrusion pellets supplemented with 12 (group I) or 88 (group II)mg/100g of α-tocopherol (α-Toc) for 46 days and then injected with the causative bacteria of fish jaundice. Changes in hematological values, bilirubin, α-Toc and ascorbic acid (ASA) contents and 2-thiobarbituric acid reactive substances (TEARS) values in the liver and plasma were analyzed. Growth rate and feeding efficiency were not significantly different between the groups. Seven days after infection, mortality was 0 and 40% in group I and II, respectively. The infection brought about hemolysis and jaundice in both fish. Judging from mortality and bilirubin contents in the plasma, jaundice was more serious in the fish of group II than in fish of group I. Considering prooxidant activity of α-Toc, this result might be caused by high α-Toc accumulation and low ascorbic acid contents in group II fish tissues.

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Species identification of 1, 048 eel individuals, collected in the natural waters of middle and western Japan from August 1997 to February 1998, has been performed by polymerase chain reaction (PCR) of the mitochondrial DNA (mtDNA) cytochrome b region. The majority of the individuals (832, 79.4%) were identified as Japanese eel Anguilla japonica. The other individuals (216, 20.6%) were thought to be European eel A. anguilla based on the analysis of PCR restriction fragment length polymorphism (PCR-RFLP). The European eels were found in the samples from Shinjiko Lake (161 out of 513, 31.4%) and Mikawa Bay (55 out of 443, 12.4%). European eel is not a native species in Japan. The possible reasons for the existence of this species in the natural waters of Japan and its influence on the natural resource of Japanese eel are discussed.

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Filtrable pathogens infecting the phytoplankton Alexandrium catenella and Tetraselmis sp. were screened from coastal seawater on the mouth of Funka Bay, Hokkaido, Japan from 1993 to 1994. Growth suppression against these phytoplankton species was observed in the seawater samples collected during September and October 1993. The growth of A. catenella was suppressed from 40 to 45%, and that of Tetraselmis sp. was suppressed from 20 to 30%. Re-inoculation of the culture filtrate of growth-suppressed phytoplankton after passing the culture through a 0.22-μm filter also caused growth suppression of the fresh culture. However, these effects disappeared after several treatments including heating at 50°C for 30min, exposure to acidic conditions below pH 5.0, passing through a 0.05-μm filter, and Proteinase K and RNase treatment. Cell free extracts of the growth-suppressed phytoplankton caused the same extent of growth suppression. Electron microscopic observation of A. catenella cells that were lead to the growth suppression revealed that the cells were severely damaged, whereas no virus-like particles or bacterial cells were observed. Growth suppression was observed in a fresh culture ofA. catenella and an axenic culture of Gymnodinium mikimotoi by the growth suppressed Tetraselmis sp. culture filtrate, and theA. catenella culture filtrate affected the growth of Tetraselmis sp. and an axenic culture of G. mikimotoi. However, the growth suppression or inhibition was not observed in fresh cultures of Prorocentrum micans, P. minimum, A. tamarense, G. mikimotoi, Chattonella antiqua, C. marina, and Heterosigma akashiwo. These results suggested that unique filterable pathogens might be found in the seawater samples.

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Using the hydroacoustic method with a 38kHz scientific echo sounding system, the diel vertical movement of the deep scattering layer (DSL) in I-Lan Bay, northeastern Taiwan, was studied on April 13_??_15 and June 12-14, 1997. The DSL started to descend about 30 minutes before sun rise at a speed of 1.4-1.7m/min and resided at 180 to 280m in the daytime. It started to ascend ca. 30 min before sun set at a speed of 1.5-1.9m/min and stayed at lO to 150m at night. Plankton samples were simultaneously collected by an IKMT sampler to determine the species composition. The dominant species (ca.>1.5cm) were Sergia lucens and Pasiphaea japonica, which made up 89.3% of the catch. The mean packing density during the daytime was about 3 times higher than that at night.

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Yellowfln tuna Thunnus albacares larvae were reared from hatching beyond metamorphosis in May and June 1996. The larval size was 2.65mm SL at just after hatching and 27.68mm SL on Day 37. Transformation to juveniles occurred around 30 days after hatching at about 13mm SL. The larvae initially fed on rotifers since Day 4, on fish larvae and Artemia nauplii since Day 16, and then on frozen fish and minced fish meat. The primitive digestive system differentiated on Day 4. The gastric gland and pyloric caeca first appeared on Day 14 and 16, respectively. The pharyngeal and jaw teeth became fully functional synchronized with gastric gland differentiation. The number of gastric glands and pyloric caeca and volume of the gastric blind sac increased markedly toward the juvenile stage. Although external morphological development of yellowfin tuna resembled to that of other marine fishes hatched from pelagic eggs, the digestive system developed precociously. The rapid development of the digestive system allows the early appearance of piscivory which can support the high growth potential as shown in other scombrid fishes.

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Spinal motoneurons of the axial muscles and dorsal root ganglionic neurons in glass eels of the Japanese eel Anguilla japonica were visualized by means of retrograde labeling with horseradish peroxidase (HRP). HRP-labeled spinal motoneurons were divided into two classes, “large” and “small”, based on their soma size and location in the spinal cord. The “large” motoneurons were located near the central canal in the dorsomedial part of the motor column and had extensive dendritic arborizations in the lateral neuropil layer of the cord. On the other hand, the “small” motoneurons were distributed over the whole area of the motor column, although relatively small cells in the “small” motoneuron group tended to be located in the ventrolateral part of the motor column. Presumptive somatic sensory neurons were labeled in the dorsal root ganglia which were situated ventrolateral to the spinal cord. The dorsal root ganglion was located just peripheral to the meeting of the dorsal root and the ventral root, and hence the motor axons traveled through the ganglion. The present observations revealed that no substantial anatomical changes in the spinal motoneurons of the axial muscles and the dorsal root ganglionic neurons of the Japanese eels occur during the metamorphic period, from the leptocephalus to the glass eel, during which time the eels undergo drastic changes of the somatic structures.

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The recent status of total phosphorus loading (T-P) from carp culture was evaluated by feeding fingerling carp (average weight 12.4±0.4g, duplicate tanks, 4 weeks at 23-25°C) six commercial diets used in Lake Kasumigaura (Ibaragi Prefecture, Japan) during 1996. The T-P was determined by employing three methods based on 1) water extractable phosphorus (P), 2) P absorption, and 3) P retention. The total P contents of six diets ranged from 1.07 to 2.09% and the absorption rates were 26.9 to 37.3%, being close to the amount of P extracted with deionized water. Growth performances were markedly different and generally high in fish fed diets containing 0.6-0.8% available P. The values for T-P between those calculated based on the water extractable P and absorption rates of dietary P were nearly identical whereas the values based on retention were slightly higher. The difference between the total amount of P given to fish and the amount of P retained in fish body can be regarded as T-P onto the environment. Therefore, the rate of P retention should be employed in the practical estimation of T-P from carp culture operation. The T-P (based on retention) varied greatly between the diets and ranged from 9.1 to 18.8kg/t carp production (13.6 on average) among the diet groups. A high lipid content was observed in the whole body of fish fed diets with low amounts of available P as a typical P deficiency symptom.

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To estimate parameters of a variety of DeLury's models by maximum likelihood method, the probability distribution of catch should be specified. But this is not a straightforward procedure because it is difficult to determine which distribution is a true representation of the catch variation. Taylor's Power Law covers a wide range of distributions from regular through random to aggregated. A generalized DeLury's method based on the law was proposed and applied to the catch-effort data of the purse seine fishery for a pelagic fish species in southern Lake Tanganyika. Dynamics models with variable catchability and natural mortality were given for the fish population. Binomial and negative binomial distributions were also considered for comparison purposes. Estimates of parameters indicated an aggregated distribution of the fish. Among the three models, Taylor's Power Law model was the optimal with the lowest AIC and the best fit to the data, which suggested its wide applicability.

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Six semi-purified casein based diets were formulated to contain either a complete mineral mixture (control) or mineral premixes from which a specific test mineral was deleted to obtain phosphorus(P)-free, magnesium(Mg)-free, iron(Fe)-free, zinc(Zn)-free, or manganese(Mn)-free diets. These diets were fed to juvenile milkfish (mean initial weight 2.60±0.08g) for a 22-week experimental period. Final mean percent weight gain ranged from 1022 to 1379% with P-free (1022%) and Fe-free (1066%) diets obtaining a significantly lower weight gain (p<0.01) than the control diet (1270%). Survival was greater than 90% and did not differ significantly among treatments.
Upon termination of the growth experiment, milkfish flesh, bones, and combined samples of head, skin, and scales were dissected and analyzed for ash, P, Ca, Mg, Fe, Zn, and Mn content. The deletion of P or Fe from mineral mixture lowered P content in flesh and bone. Zn content in bone of fish was also lowered by exclusion of Zn, Mn, Mg or Fe. The result of this study demonstrated that it is necessary to supplement P and Fe even to semi-purified casein based diets.

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In order to investigate diel patterns of vertical distribution and feeding of Japanese Spanish mackerel Scomberomorus niphonius larvae, day and night depth-discrete samplings were conducted in Hiuchi-nada, the central waters of the Seto Inland Sea, in June 1996 and 1997.
Japanese Spanish mackerel larvae exhibited a developmental stage related diel pattern of vertical distribution. Yolk-sac larvae did not show marked vertical movements, but diel vertical movement became evident after yolk absorption. During the day most larvae were caught in middle and bottom tows. In contrast a high percentages of larvae were captured in the upper-layer tows at night. Volumes of swim bladder of the larvae collected at night were larger than those in day, indicating larval dispersion upward by inflation of their swim bladder after dusk.
The diet of Japanese Spanish mackerel larvae consisted exclusively of other fish larvae. Clupeiformes fish were the dominant prey, followed by Gobiidae larvae. Percentage of stomachs with food and stomach fullness was high in day and peaked at dusk, then decreased throughout night. Stomach-contents of Japanese Spanish mackerel larvae became more diverse from dusk to midnight, primarily due to occurrence of Callionymidae and chub mackerel Scomber japonicus larvae which did not appear in stomachs during the day. Though primarily a daylight feeder, feeding at dusk may be very important since prey may be less active and more efficiently captured.

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Attempts are made to elucidate the optimal dietary requirement of vitamin C in thornfish Terapon jarbua cultured at 28, 32 and 36°C, separately. The fish were fed diets with 0, 80, 400 and 2000mg/kg vitamin C-supplement for 8 weeks. The growth was the best when the fish fed diet with 400mg/kg vitamin C-supplement and cultured at 36°C. The mortality of fish increased with increasing water temperature, but decreased with increasing the amount of vitamin C supplemented in diets. The deformed fish appeared at 36°C when fish were fed diet supplemented no more than 80mg/kg vitamin C. The vitamin C level and hydroxyproline/proline ratio in the fish tissues increased with increasing the amount of vitamin C supplemented in diets. Both variations of vitamin C level and hydroxyproline/proline ratio in thornfish were similar to each other. Judging from the data of growth, feed conversion factor, vitamin C level and hydroxyproline/proline ratio, the optimal level of vitamin C in the diet for thornfish was 80mg/kg when fish were cultured at 28 and 32°C, but it had to be elevated to 400mg/kg when fish were cultured at 36°C.

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A live haploid-diploid mosaic charr Salvelinus leucomaenis, in which 89% of erythrocytes were unusually small, was found by chance. This individual was externally normal in shape and grew to the adult size (335mm body length, 324g body weight). Flow cytometry for DNA content revealed that large population of cells in blood, liver, and spleen were haploid, whereas those in brain were diploid. Thus, this individual was concluded to be a mosaic consisted of two types of cells with different ploidies. These results suggested that haploid cells may have normal function in the mosaic environment including diploid cells. Histological observation showed that this mosaic charr was a female with ovaries filled with degenerating and degenerated oocytes which showed various abnormalities and was likely to lack normal reproductive ability, even if it had survived longer.

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Lyophilized extracellular mucilage (LEM) powder was recovered from Klebsiella oxytoca CF154 culture, and the yield was approximately 0.8g per liter of the culture medium. Relative viscosity (RV) increased as the concentration of LEM aqueous solution increased from 0.0 to 0.5%. Factors affecting RV of 0.2% LEM solution showed that the RV was stable over a pH range of 4 to 9, although it dropped sharply outside of this range. The higher NaCl concentration (0-5%) in LEM solutions was, the lower RV of LEM solutions was. RV of 0.2% LEM solution decreased as the temperature increased from 10 to 80°C. Changes in molecular flexibility, which was indicated as changes in activation energy of 0.2% LEM solution, depended on temperature. Results from Sephacryl S-400 gel permeation chromatography (GPC) indicate that LEM is a mixture of protein-polysaccharide complexes of which the dominant fraction (85%) has a molecular weight ranging from 1.5-1.8 MDa in the polysaccharide moiety. HPLC analysis suggested that the major sugars in this dominant fraction were mannose, galactose, glucose, and arabinose. In addition, there exists uronic acid at 6.3% in this dominant fraction.

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Isotherms of flavored mackerel slice were determined at higher temperatures by a dew point sensor hygrometer. The hygrometer, whose parts were all custom-made, was designed, assembled and calibrated by saturated salt solutions in the lab. The calibration results showed that at temperatures below 50°C the dew point measurements were accurate within ±0.2°C, which was the accumulation of instrumental errors, while at 60 and 70°C the errors were between -0.8 and 0.2°C, Quadratic equations were derived and used for correction for measurements at 60 and 70°C. Desorption isotherms of flavored mackerel were relatively invariant in the range of 30 to 50°C. The water activity increased as temperature decreased in the temperature range of 60 to 70°C. GAB (Guggenheim-Anderson-de Boer) is the best fitted correlation of the 8 sorption isotherm models tested. All the fitting parameters were obtained and listed in the report in the range of 30 to 70°C. By adjusting 3 parameters the fittest curves for GAB model resulted in R-square value of as high as 0.986 on average in the temperature range studied.

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The rheological properties offish-meat gel with or without starch were characterized by large-defor-mation tests. We conducted a compression test with up to 70% deformation. The results were analyzed by the Mooney-Rivlin equation: f=(2C₁+2C₂/λ)(λ-1/λ²), where f is the stress, λ is the draw ratio, and C₁ and C₂ are the constants. In Mooney-Rivlin plots of the case considered as two- and three-terms, the theoretical curves show excellent correspondence with experimental plots in the initial-strain region. To investigate the adding effect of wheat starch on the fish-meat gel's elasticity, the water amount added into sample was controlled by considering water-absorbing capacity of wheat starch at 60°C and 90°C. In doing so, the water content of each gel was adjusted to be the same. Here the effect of adding starch on the fish-meat gel's elasticity was interpreted by the Mooney-Rivlin equation. The result showed that the effect of added starch must be analyzed according to composition before and after heating. We thus obtained the tendency whereby the experimental values agreed with the theoretical values in the initial region.

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The rheological properties of fish-meat gels were characterized by applying the following three cases of large deformation theory: the original Mooney-Rivlin equation (Eq. 1), f=2(C₁+C₂/λ) (λ-1/λ²), Eq. 2 which considers the volume change, _??_, in Eq. 1 at each compression step, f=2(C₁+C₂ _??_/λ)(λ-_??_/λ²), and Eq. 3 which considers the volume change as a function of β and μ, directly in Eq. 1, f=C₁(2λ-4βμ)+C₂(4β²λ-4βλ²μ-4β³μ), where f is the stress, λ is the draw ratio, and C₁, and C₂ are the constants. We conducted a compression test with up to 70% strain and a compressionrecovering test with up to 20, 30, 40, 50, 60 and 70% strain. The theoretical values considering the volume change of the gel with strain agreed more exactly with the experimental values than those obtained by the original Mooney-Rivlin equation. It was more useful to use Eq. 3 than Eqs. 1 and 2 for calculating the values of the constants C₁ and C₂. The usefulness of the relationship between the linearity of stress with strain and C₂/C₁ values was confirmed under both constant stress and constant strain conditions.

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The structure and transcription of the genes for polypeptide chain elongation factor 1α (EF 1α) were investigated in the medaka Oryzias latipes. The genes were tandemly arrayed, and tentatively named EF 1α-A and EF 1α-B according to the arrangement from 5' terminal, respectively.^*5 The Southern blot analysis indicated that no other gene of EF 1α existed per haploid genome. The EF 1α-A consisted of 8 exons and 7 introns and the sequence of its exons was completely identical to the EF 1α cDNA isolated from medaka liver. The primer extension analysis on EF 1α-A revealed that transcription of EF 1α gene was performed in TATA-independent manner. In one day medaka embryo, the 5' upstream region of EF 1α-A showed about 4 times stronger promoter activity than cytomegalovirus promoter, indicating that the 5' upstream region of EF 1α-A could be a good promoter for expressing the foreign gene in the transgenic fish. On the other hand, 5' upstream region of EF 1α-B did not show any promoter activity.

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cDNA clones encoding tropomyosin of akazara scallop Chlamys nipponensis akazara striated adductor muscle were isolated and sequenced. The largest cDNA obtained is composed of 1, 995 bp including an open reading frame of 852 bp at nucleotide positions 27-878, which deduced amino acid sequence of 284 residues with a calculated molecular weight of 32, 540. According to database searches on NBRF-PIR 49.0 and GenBank, the amino acid sequence showed higher homology of 73% and 70% to bloodfluke planorb tropomyosin and mussel anterior byssus retractor muscle tropomyosin, respectively, and considerably high homology of 53% and 51% to rabbit α- and β-tropomyosins, respectively. The sequences corresponding to the critical region for actin-binding (residues 1-9) and troponin-T-binding region (near residues 150-180) of rabbit α-tropomyosin are conserved also in akazara scallop tropomyosin. As the nine residues at both of the N-terminus and C-terminus are generally regarded to form a head-to-tail interaction region, the residues at the N-terminus of akazara scallop tropomyosin show high sequence homology to those of various muscle tropomyosins. However, those at the C-terminus show lower sequence homology than those of vertebrate tropomyosin. Thus, head-to-tail interaction of akazara scallop tropomyosin may be different from rabbit tropomyosin on account of low homology of the C-terminal sequence.

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The dorsal part of ordinary muscle excised from fresh milkfish was salt-ground in the presence of eleven food additives, i. e., egg white, sorbitol, CaCl₂, CaCO₃, H₂O₂, KBrO₃, ascorbic acid, sodium ascorbate, sodium erythorbate, cystine, and cysteine. Kamaboko was made through setting and heating procedures, and then, the gel strength (maximum stress and deformation), the amount of expressible drip, pH, and tristimulus color values (L, a and b) of these products were compared. The results obtained showed that the addition of 1% sorbitol was effective enough to obtain kamaboko of high lightness and gel strength, whereas addition of H₂O₂, ascorbic acid, sodium erythorbate, and cystine improved the lightness of kamaboko. On the other hand, egg white, CaCl₂, and KBrO₃ were found to be ineffective for the improvement of quality. Calcium carbonate decreased the lightness of the products.

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