Boring clam, one of the giant clams is resource which has decreased markedly. For main-tenance of this resource Okinawa Prefecture has established harvesting regulations. Data on the boring clams, such as relation between shell length and wet weight of soft part or gonad, and sexual differentiations are summarized. Young shells less than 5.5cm in shell length are male, and larger ones are hermaphroditic. Wet weight of matured gonad in clams of 6cm shell length are only 3g, but attain 10.6g in 8cm clams. Wet weights of edible portion are 11.3g and 25.3g for 6 and 8cm clams respectively. The prohibition of harvesting clams under 8cm in shell length is based on the calculation of the number of reproductive years necessary to maintain and restore the population. The short diameter of the adductor muscle (1.4cm) may be substituted for shell length when the shell has been removed.

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The sea around Okinawa Prefecture is northern border for the distribution of boring clams. Spawning is limited to summer, and the cold seasons are rest periods. In April when the monthly mean seawater temperature reaches above 25°C, the gonads of clams turn active. Some clams mature by the beginning of June. But, there are great individual variations. Matured clams undergo spontaneous or partial spawning. With the arrival of the first typhoon, usually in August, clams discharge all remaining eggs and sperm uselessly. In an exceptional year without typhoons, the complete discharge of eggs and sperm occurs when there is a great decrease in water tempera-tures by November. The actual spawning seasons of the boring clams are from June to August. This is the period when the harvesting of the boring clams is prohibited in Okinawa Prefecture.

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Current measurements were carried out at three stations on the continental shelf off the Tajima coast, in the Japan Sea, during about 17 days in the winter of 1981, to study the structure and variability of the coastal current. Because of relatively little stratification, the barotropic flow was predominant rather than the baroclinic flow. The mean current during the observational period is eastward, and this current is considered as the first branch of the Tsushima Current. The velocity near the current axis of the first branch reached to about 0.5kt. The measurements showed that the current variations were highly coherent with the variations of wind and coastal sea level. Alongshore currents were in phase with the coastal sea level, and lagged behind the alongshore wind by about 15 hours. Therefore, the current and sea level variations can be con-sidered to be mainly forced by wind.

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The early growth, yolk and oil globule resorption, early morphological and behavioral de-velopment, and initial feeding of hatchery-raised Lates calcarifer were studied. Based on the developmental events and the energy the reby utilized, the early life history of this species can be broken down into the following five phases: 1) rapid early growth due to rapid yolk resorption (from hatching to about 15 hr after hatching (TAH); 2) morphological differentiation and slowgrowth based on energy from yolk (to about 50 h TAH when the yolk is exhausted); 3) slow growth with initiation of feeding and swimming activities, based on energy from oil globule and from exogenous food (to about 110 h TAH); 4) accelerated growth and effective feeding and swimming based on the same two sources of energy as in the preceding stage (up to about 120-140 h TAH when the oil globule is exhausted); and 5) accelerated growth, effective feeding and swimming and further development based solely on exogenous energy (beyond 140 h TAIT).

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From September to October in 1984, an epizootic occurred among cultured ayu Plecogrossus altivelis in Yamaguchi prefecture. The typical symptoms of the diseased ayu were congestion and swelling of anus, congestion of pectoral fin-base, subcutaneous hemorrhage of caudal peduncle. A bacterium was isolated from the kidney of all the diseased ayu. By infectivity trials the bacterium was proved to be pathogenic to ayu. The LD₅₀-value of an isolate to ayu was revealed 1.4×104 cells/g (b.w.) by intraperitoneal injection. These organisms were gram-negative, non-sporing rods with a single polar flagellum, and usually 0.7 to 0.8 by 0.8 to 3.0μm in size. On nutrient agar colonies developed within 24 hours at 25°C. The organisms grew at temperatures between 15 and 37°C. But no growth occurred 5°C ar 42°C. Growth occurred on SS agar, MacConkey agar and Aronson agar. The organisms gave positive oxidase and catalase reaction, utilized glucose, salicin and some carbohydrates fermentatively in Hugh-Leifson's medium and produce gas from many carbohydrates. IMViC reactions were (+(3/4), +, +, -), Hydrogen sulfide, 2, 3- butandiol dehydrase, elastase were produced. As a sole carbon source, L-arginine, L-histidine, L-glutamic acid, L-serine, saccharose, gluconate were utilized. The G+C content of the DNA was 62.0 mol% for a selected strain.
From the above-mentioned properties, the isolates should be identified as Aeromonas hydrophila, although the organisms are sensitive to the vibriostatic agent O/129.

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The juxtaglomerular (JG) cells in the mammalian kidneys are known to secrete a kidney hormone called renin. JG cells are present also in the kidneys of holocephalian and teleostean fishes. However, the kidneys of cyclostomes and elasmobranchs are lacking in these cells. The present histolgical investigations using Bowie's stain were performed to clarify whether or not JG cells are present in the kidneys of South American freshwater stingrays Potamotrygon spp., the sterlet Acipenser ruthnus, the bester (intergeneric hybri of A.ruthenus ?? ×Huso huso ?? ), and the longnose gar Lepisosteus osseus. However, JG cells were not detectable in the kidneys of any these fishes lnvestigated.

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Fish behaviour in the set-net fishing grounds of Sagami Bay was investigated with the scanning sonaz in 1983 and 1984. Two different types of set-nets were employed in those fishing grounds; one is with one trap which was set in the undulating sea bottom having a steep slope, the other was two trapped type in the flat bottom having a gentle slope.
In the one trapped set-net fishing ground, the fish schools mainly approach the gear in the same direction as the current. They tend to take a migrating route along the deep and enter the set-net, On the other hand, in the two trapped set-net fishing ground, the fish schools could be observed to be entrapped into the set-net along the leader net, but not showing any certain migrating route.
The designs of these set-nets were considered to be well adapted to the migrating behaviour that had been influenced by the topography of the sea bottom and the current in the fishiffg grounds.

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Mass mortalities had been frequently occurring in the early stage of development of hatched black sea bream Acanthopagrus schlegeli at hatcheries in west Japan. Normal, morbid and dead fish were collected at three, six and fourteen days after hatching at Kochi Prefectural Fish Farming Center during the period from April to June 1984. After homogenation of these fish, total number of bacteria and bacterial flora were determinded. Number of total bacteria was about ten times greater in morbid fish than in normal fish after an outbreak of the disease. Three species, Vibrio alginolyticus, Vibrio nereis, and Alcaligenes Cupidus were found dominant in the bacterial flora of morbid fish. Using waterbone infection and oral infection by feeding rotifer, Brachianious plicalitis artificially infected with these microorganisms, V. alginolyticus and A. cupidus gave high mortality in norsmal fish but not V. nereis. The results indicate that V. alginolyticus and A. cupidus may cause the mass mortality in black sea bream fry.

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This paper examined variations by sex and body size in the avoidance tests of LAS (sodium linear laurylbenzene sulfonate) and fenitrothion using a fish, adult medaka Oryzias latipes, in a small chamber system with a bisymmetrie parallel-flow. Although these avoidance tests were re-peated many times in different seasons, the reproducibility of the tests was excellent. No significant difference was found in between the male and female of same size. However, the avoidance con-centrations of small medaka were apparently lower than those of large medaka, indicating that avoidance response to the aquatic contaminants may vary significantly with fish body size. There-fore, comparison of avoidance tests among different species of fish should take into consideration the fish size.

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Tagging experiments were made with kuruma prawn Penaeus japonicus in the central part of Matoya Bay over the period of 1982 to 1984 to evaluate its natural mortality in winter. The 2358 prawns (A group) and 1163 prawns (B group) were tagged with an anchor-tag and released in the bay over the periods of autumn, 1982, to spring, 1983 and of autumn, 1983, to spring, 1984, re-spectively. The tagged prawns were recaptured in the three fishing areas, i. e., the center of Matoya Bay; its mouth and the open sea. The prawns released in autumn of a year were recaptured mainly in the central part of the hay over the period of April to 3uly in the following year. On the other hand, the ones in spring of a year were recaptured chiefly there up to July in that year. In Agroup, the recapture rates of sub-groups exponentially decreased with T-Tw in which T and Tw referred to the mean recapture time and the length of winter, respectively. The rates of B group also showed a tendency similar to that of A group. These findings suggest that there is little mortality among the tagged prawns at least in winter between December and March.

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The carp myosin B solution was frozen and stored at -3, -5, -10 and -20°C, in order to make clear the freeze denaturation of the protein caused by the concentrated KCI solution on the basis of the thermal inactivation mode of Ca-ATPase. The same manner was also carried out for the myosin B in 1.33M KCI solution under the unfreezing conditions of +3 and -5°C.
In the case of -3 and -20°C frozen storages, the thermal inactivation mode of Ca-ATPase changed from the single-phased first-order plots to the two-phased first-order plots after 11 and 3 days, respectively. In the case of -5 and -10°C frozen storages, the same phenomenon occurred after 6.5h; the apparent rate was larger at -10°C than at -5°C. The order of influence on storage temperature was -10°C>-5°C>-3°C, in the range-of-3 ?? -10°C. When the myosin B in 1.33M KCI solution was stored at-5°C (unfreezing condition), the two-phased first-order inactivation mode was found after 7h, and at +3°C after 26h. The single-phased first-order inactivation mode was restored on addition of carp F-actin to the myosin B which was changed to show the two-phased first-order one after frozen storage at -5°C for 12h and after unfrozen storage in 1.33M KCI solution at -5°C for 9h.
From these findings, we concluded that a portion of F-actin in carp myosin B which was frozen and stored in the range of -3 ?? -10°C, was denatured as a result of the exposure to con-centrated KCI solution; under this range, a lower temperature that is a higher KCI concentration had an accelerating effect on the denaturation of F-actin.

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Alaska pollack myofibrils were suspended or dissolved in the media containing varied con-centrations of CaCl₂ and NaCl conferring different ionic strengths, and the water-holding capacity (WHC) of myofibrils and thermal inactivation rate (K_D)of myofibrillar Ca-ATPase were studied.
A large decrease in WHC of myofibrils was found to occur when the ionic strength (I) of medium remained low (I=0.05-0.10) and CaCl₂ was further added to the medium at the con-centration of less than 15m_M.
When CaCl₂ was added to the myofibrils in the media of various ionic strength, khe K_D was increascd several times by the addition of CaCl₂ regardlless of the ionic strength of the media. After removal of CaCl₂ by dialysis, F-actin was added to the myofibrils with an equal amount of myosin content in it. The K_D was nearly recovered and equal to that of the untreated myofibrils with CaCl₂.
It was thus suggested that the actin portion in the myofibrils of alaska pollack was domi-nantly denatured through the reaction with CaCl₂.

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The proximate composition of various tissues and the fatty acid composition of their lipids in Cyprinidae in Lake Biwa were determined in order to evaluate the nutritive value of fresh water fish. The fishes examined were gengoroubuna, nigorobuna, koi, hasu, oikawa, honmoroko and ugi.
The results obtained were as follows.
(1) The contents of moisture, crude ash, crude protein and crude lipid in edible portions were 67.8-81.7, 0.9-3.2, 14.5-20.6 and 1.2-12.5%, respectively. The whole body, dressed or semi-dressed portion and fillet of small-sized fishes such as hasu, oikawa and honmoroko were relatively rich in crude ash and crude lipid.
(2) The lipids of the edible portions were rich in palmitic acid (C_16:0), palmitoleic acid (C_16:1ω₉)and oleic acid (C_18:1ω₉).
(3) The content of total polyunsaturated fatty acid was lower in lipids of muscles or whole bodies of Cyprinidae than in those of the muscles of marine fishes.

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Two series of rearing experiments were undertaken for the check of accumulation and ex-cretion of cadmium (Cd) on Himedaka Oryzias latipes.
In one of two series, 10 fish of Himedaka (average length, weight, and contont of Cd were 2cm, 0.2g, and 0.25ppm, respectively)took 3-10 ppm of Cd in each body within 20-24h ofrearing in the experimental solution including 1.1 ppm of Cd. In other series, during the rearing of 10 fish of Himedaka in the pure solution, 15, 000 of Artemia salina LINNAEUS having 19 ppm of Cd were fed into the pure water for 20 min. In the case of 5h, two feeding of 15, 000 of the Artemia into the pure solution, 3 ppm of Cd was accumulated in the fish body. The Anemia as the feeding material, which had 19 ppm of Cd in the body, contained 2-4 ppm of Cd. By using both Cd-accumulated fish, the rate of Cd excretion was examined in the pure water after 72h of rear-ing. In both accumulations of Cd via branchial and via oral, the excretion of Cd occured im-mediately after the transfer of fish into the pure water. The excretion of Cd was especially ob-served as the decrease of letter L curve on the fish containing above 3 ppm of Cd. The concentra-tion of Cd in the fish body decreased to 1-3 ppm after 72h of rearing with pure water, Cd accumulated via oral intake excreted outside the fish body much faster than that of via branchial accumulation. The rate of fatality was lower in the fish with oral intake than that of branchial intake, even if the content of Cd in the body was the same at both intakes. The rate of fatality was also low in the Himedaka which contained high amount of Fe in the body.

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In order to understand the function of intertidal zone in nutritive circulation in the sur-rounding water, budgets of nitrogen, phosphorus and suspended solid on an intertidal flat were investigated in summer through the use of box model. Their distributions of concentration were observed and their supplies from the background were estimated. It was found that the intertidal flat is a net sink of nutrients due to fixation by aquatic plants and trapping by bentic animals rather than a net source of nutrient salts due to high potential of mineralization of organic substances by bacteria and microfauna under aerobic condition. Thus, an intertidal zone probably functions in summer as a buffer for the surrounding water against the nutritive load from the land.

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Sardine fibers were produced from round sardine and sodium alginate. Water holding capacity and appearance of fibers were improved by the use of a CaCl₂ solution as a coagulant. Fibers were flexible and similar to buckwheat noodles in texture. They had a weak taste and were non-peculiar.
As the amount of added sodium alginate and the concentration of CaCl₂ solution increased, shear values of fibers became larger. Consequently, shear values of fibers were expressed by two-variable polynomial on the concentration of CaCl₂ solution and the amount of added sodium alginate, and the polynomial satisfactorily predicted shear values observed in additional experi-ment.
By cooking in boiling water, moisture content of fibers was decreased, the appearance be-came coarse, and the shear values were incfrased. By the addition of Na₄P₂O₇, shear value, appearance and water holding capacity were improved.
In fiber production, sodium alginate fibers without sardine were too tough or, on the con-trary, were formed imperfectly. These findings suggest that the properties of protein included in sardine would be also related to sardine fiber formation.

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The ordinary and dark muscles of albacore, yellowfin and skipjack tunas were examined for protein composition, along with the contents of myoglobin (Mb), and ATP and related compounds. The stroma protein and Mb contents were around 5 and 10-40 times, respectively, higher in the dark than in the ordinary muscle in the three fishes. The K value, a parameter of freshness, of the dark muscle was 3-14 times higher than that of the ordinary muscle in every analyzed specimen.
The proportions of collagen to elastin in connective tissues were fairly constant regardless of the species and the part of the muscle, 88-98:2-12.

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In order to clarify the causes of the improvement of the growth and feed efficiency by the supplement of seaweed in the previous study, diets with and without5% Ascophy11um, 5% and 10% Wakame were fed once to red sea bream at a fixed level, and the changes in percent absorption of carbohydrate and protein and in blood sugar and plasma free amino-N levels after the feeding were determined.
The supplement of seaweed into the diets at a 5% level delayed the absorption of carbohydrate and protein, and the blood sugar and plasma free amino-N levels did not increase between the 2nd and 5th hour after the feeding.
From these findings, it can be assumed that the dietary nutrients are utilized effectively by this delaying effect of seaweed, thus the growth and feed efficiency of red sea bream are improved.

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The effect of sarcoplasmic proteins (Sp) on rheological properties of heat-induced fish meat gel was examined, using a model system.
Actomyosin (AM) and Sp were prepared from the muscle of sea bass Latsolabrax japonicus, mixed with various proportions with 3% NaCl, and heated at °C for 15min (H-gel), or further retorted (steamed) at 120°C for 4min (HR-gel). The gels formed were examined for rheological properties by organoleptic tests, rheometer, differential scanning calorimeter, etc.
HR-gel from 100% AM was more fragile and showed less water-holding capacity, compared to the H-gel. It was not the case with AM+Sp: HR-gel showed more springiness and higher water-holding capacity than H-gel, as also supported by differential scanning calorimetry.
It was concluded from these results that the modes of interaction of Sp with AM during heat-induced gel formation widely differ from each other depending upon the conditions applied.

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The protective effect of ATP-MgCl₂ on the thermal denaturation of rabbit and tilapia myosins was studied by measuring the change in its Ca-ATPase activity.
When myosin (0.5M KCI, pH 7.5) was incubated in the presence of varied concentrations (0-1.0mM) of ATP-MgCl₂, Ca-ATPase activity changed in two steps: an early unchanged stage, followed by a rapid inactivation stage. The time required for inducing the rapid inactivation of Ca-ATPase was equal to the time needed for most of the ATP hydrolyzed in the medium. When myosin was incubated in the presence of a fixed concentration of ATP-MgCl₂ with ATP-regenerating system (phosphoenol pyruvate plus pyruvate kinase), Ca-ATPase was slowly inactivated in a single first order process and the inactivation rate was decreased as the con-centration of ATP-MgCl₂ increased (0-0.3mM). It was thus found that the rate decreased to one-tenth of the initial value upon addition of 0.1mM ATP-MgCl₂. In addition, the protective effect of ATP-MgCl2 against thermal inactivation was much stronger for the myosin in 0.1M KCI-medium than for that in the O.5M KCI-medium.
The protective effect of ATP-MgCl₂ on the denaturation of myofibrillar protein in pre-rigor fish muscle was discussed.

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Influence of death condition and freshness of fish on the gel-forming properties of their muscle was investigated. Strugglingly killed common mackerels were not only poorer in the gelling potential but also much higher in the modori susceptibility than instantaneously killed ones. When passing through the rigor stage instantaneously killed tilapia increased the modori susceptibility, whereas the gelling potential was not decreased. According to an evidence that the modori sus-ceptibility of myofibrils is increased by a weak acid treatment (pH 6.0), the cause of the abovementioned variability in the gel-forming properties was attributed to the decrease of the muscle pH to 6.0 or less.

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pH and metal ions influencing the antifungal action of salmine sulfate on mold organisms were studied. The activity of salmine sulfate was greatly decreased on acidic pH and no inhibition of growth was observed at pH 4 and below. In neutral and alkaline media, protamine was found to exert fungicidal action on mold species. The ionic strength of buffer greatly affected the in-hibitory activity of protamine. An increase the ionic concentration resnited in an increase in survivability of the organism. In 0.5M phosphate buffer, the lethal activity of salmine sulfate was greatly reduced. Although the effect of molarity on the fungicidal activity varied somewhat, depending on the salt used, higher ionic strength in general led to increase survival of Eurorium repens.

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Intraperitoneal administration of 250mg/kg of PCB (Aroclor 1248) to carp stimulated the metabolism of progesterone, estradiol-17β and testosterone by hepatopancreatic microsomes: the activity of progesterone hydroxylase was increased by 148% in the PCB-treated group, while those of estradiol-17β and testosterone hydroxylases were elevated by 30% and 108%, respectively. A significant reduction in plasma sex hormone levels was also observed in the fish treated with PCB: the plasma concentrations of progesterone and estradiol-17β in female carp were lowered by 56% and 26%, respectively, while that of testosterone in male carp was reduced by 53%. This reduc-tion in circulating sex hormones is probably attributable to elevated metabolism of sex hormones in the hepatopancreas. The ability of PCB to alter the plasma levels of sex hormones raises the possibility that PCB accumulated in fish at high concentrations colud have a deleterious effect on fish reproduction.

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In order to make clear the influence of biological factors on uptake, retention and excretion of ⁵⁴Mn, perry whelks were exposed to the radioisotope through ambient seawater, being separated into female and male, and subsequently a half of the specimens were depurated in non-spiked seawater. The parameters representing accumulation phenomena, such as concentration factor at steady state (CFss), coefficient of accumulation velocity (K₀₁), turnover rate (K₁₀), biological half time (Tb), etc, were estimated from the equations of accumulation and excretion curves and compared sex-wise and among individuals.
There were no sex-dependent differences on all the parameters. But, weight-dependent differences were found on CFss and K₀₁. From the regressed relations, In CFss (or K₀₁)=In a-b ln WW, it is demonstrated that the values of two parameters increased according to de-creasing whole weight (WW) of individual. The values could remarkably be raised extrapolately in the samll size range. This weight dependence of accumulation was similar to those of bivalves except ostreids, and herbivorous and carnivorous gastropods examined previously on stable-Mncontents. The values of CFss obtained here were about 4 to 8 times higher than those of black abalones.

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Distributions of ⁵⁴Mn to various tissues of female and male of perry whelks with ripe gonads were examined in accumulation and excretion phases. The differences in ⁵⁴Mn distribution be-tween female and male could not be found on any tissues without regard to the phases, and therefore, on the whole bodies or the whole soft bodies as well. These findings differ greatly from the results obtained on Mn and/or ⁵⁴Mn distributions in bivalves and herbivorous gastropods previously reported elsewhere. The values of i-LI of various tissues were almost equal to each other irrespec-tive of sex, and between accumulation and excretion phases except conchs in which the values of i-LI decreased more rapidly than in other tissues in the latter phase. Concentrations of ⁵⁴Mn were dependent on weights of most soft tissues, and the correlations were regressed to power functions in accumulation phase. The regression lines were transformed from power functions to linear ones at certain stages in the excretion phase. The excretion curves can finally be super-imposed on the X axis when the nuclide have completely been eliminated from the tissues. Stable-Mn concentration of the ovary was significantly higher than that of the spermary as well as the bivalves and the herbivorous gastropods. A lot of eosinophilic droplets that were identified histochemically to be one of acidic mucopolysaccharides existed in the ripe ovarian tubules. This was not seen for the species whose ova and spermatozoa were discharged directly into the am-bient seawater.

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