Distinct spawning stocks of herring populations in the Far Eastern waters were examined on their sex ratios, age compositions and initial growth rates.
Most populations were the same in regards to their sex ratios, but the Atsuta population showed an unequal ratio suggesting the existence of different ecological properties.
Six populations around Hokkaido Island showed lower mean ages but higher growth rates than four northern populations which were 9-11 cm in body length at the first year of life.
Variations in the mode of life of ten populations have been classified into the following three ecological types; lake type (spawning in brackish lake and no migration), shore type (spawning in saline shore and narrow migration) and sea type (spawning in shore and extensive migration).
Those ecological characteristics seem to be closely associated with dynamics of each population of the herring in the Far Eastern waters.

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The annual reporductive rhythm of the tobinumeri-dragonet Repomucenus beniteguri was investigated for two consectuive years. In females, mean gonadosomatic index (GSI) peaked in late May (3.93%, 1986; 2.86%, 1987), and decreased to the lowest value during the summer (0.81%, 1986; 0.43%, 1987). It increased again in September, peaked in October (5.45%, 1986; 5.91%, 1987), and declined to 1.06% during the winter. About 40% of the females were ovulated in May, whereas all the females caught in October were ovulated. Ovaries were either regressed or immature in August. Changes in the GSI of males were similar to those of females, although the maximum level (0.29%) in males was very low.
In the females, plasma estradio-17 β (E2) levels exhibited seasonal changes in relation to GSI changes. Peak values of E2 were observed in May (0.79ng/ml) and October (0.78ng/ml). The lowest levels (0.17ng/ml) were detected in August. Plasma testosterone levels also increased in both spawning seasons, but the levels were very low ( ?? 0.31ng/ml). In males, plasma 11-ketotestosterone levels were detectable only in May (0.50ng/ml) and October (0.15ng/ml). Changes in plasma testosterone levels did not correlate with GSI changes in the males.

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The responsiveness of free neuromasts (pit organs), innervated by a buccal branch of the anterior lateral line nerve, the ramus buccalis, in the carp Cyprinus carpio to carbon dioxide dissolved in distilled water was studied using whole nerve and single unit recording techniques.
The stimulation of the carp pit organ with CO₂ solution produced a large phasic response followed by a long period (60-90s) of depression in impulse discharges. These temporal patterns of integrated responses were CO₂-specific and differed from those of various acids, in which an initial phasic response was followed by a plateau level of neural activity sustained during the stimulation.
The magnitude of the CO₂ responses was slightly pH-dependent, suggesting that dissolved free CO₂ may have a facilitating effect on the receptor cell.
All the single units tested responded to CO₂ and other acids with response patterns similar to those in whole nerve recordings. No specicfic single units responding to CO₂ alone were detected, showing the receptor cells to be 'generalist' in nature.

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Examination of relative growth of cephalic shield length, cephalic shield width, thorax width and abdomen length to body length revealed the occurrence of six forms of Panulirus phyllosoma, five known and one undescribed, in Japanese waters. These forms were identified as follows: Oshima's form F, which has been proposed as P. japonicus, is identical with this species and includes P. longipes which has close affinity to P. japonicus. Murano's form C is identified as P. penicillatas. Murano's form D and the authors form D' may correspond to P. versicolor and P. ornatus, respectively. Oshima's form E is suggested to be P, homarus. Because of the samall number of specimens and limited information on the morphological characteritics of P. homarus group, the specific identification of forms D, D' and E is tentative. Specific allocation of form B still remains to be investigate. Relative growth seems to be a useful method for the identification and classification of palinurid phyllosoma.

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The measurements on the reflection by a free-swimming fish shoal in a net cage and the transmission through that shoal, were carried out by using a 50kHz echo-sounder in an indoor 50 ton-water-tank. In addition, the measurements on the reflection from a fish in yaw plane were done. In the experiment, a transducer of the echo-sounder received the reflected waves, and a hydrophone received the transmitted waves. These signals were analyzed by means of a signal analyzer. Plural kurosagi Gerres oyena, with a mean folk length of 8.5cm and a mean body depth of 2.6cm, were utilized.
From the measured results, it was shown that the reflected voltage increased, and transmitted voltage was decreased, as the number of the fish increased. But the reflected voltage had irregular fluctuation, so that it was hard to estimate the fish-density from the voltage. In contrast, the transmitted voltage was very stable. After much labor, we have obtained the results showing the same conclusion as the one in the previous report, namely, it was suggested that utilizing the transmitted voltage in estimating the fish-density is effective.

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The formation of southbound skipjack fishing grounds off Touhoku sea area was studied through the use of satellite imageries and satellite-aided issues by JAFIC covering the recent six years. It was verified that the two conditions of “to be close to the warm core ring off Sanriku or the SST (sea surface temperature) boundaries” were essential to the formation. Then, by quantifying those conditions, the method to discriminate and predict the formation of fishing grounds was studies.
The discriminant variables were 1, the spatial and 2, the temporal SST gradients of a sample mesh and 3, the proximity to the current path within a warm core ring or to the SST boundary, respectively, divided by the deviation of the present SST from the favourable water temperature. On meshes sampled from the sea areas, data of variables were obtained and subjected to discriminant analysis.
Within the discriminant model thus obtained, plus sign of composite variable of a mesh discriminates and indicates that a fishing ground for skipjack is formed in the sea area represented by the mesh. The mean correct discrimination rate reached 88% for used data and 82% for new data and proved its usefulness.

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A total of eight specimens of the anguillid leptocephali were collected by TV Keiten Maru, Faculty of Fisheries, Kagoshima University, in the waters east of Luzon in June and July 1988. They were identified as seven Anguilla japonica Temminck et Schlegel, and one A. marmorata Quoy et Gaimard or A. celebesensis Kaup based on the segmental characters. The present A. japonica leptocephali were 24.0-31.8 (mean 27.4) mm TL, and were smaller than those of the previous collections. The location and month of the capture extended spatially and temporally the distribution of the Japanese eel leptocephali in the western North Pacific. The smallest specimen in the present A. japonica leptocephali, the youngest larva hitherto known from the field, was collected at a station east of Luzon (15°46.1'N, 138°42.4'E).

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The incidence of yellowtail ascites virus (YAV) was examined in wild yellowtail Seriola quinque-radiata fingerlings collected at 10 different stations along the coast of Tosa Bay in 1986. The incidence of YAV in fingerlings was 14.9% examined on CHSE-214, RTG-2, EK-1, and YTG cells, 14.5% on BF-2 cells and 8.57% on FHM cells, respectively. 47.1% of the carrier fingerlings developed ascites and their mean virus titer was 10^6.0 TCID₅₀/g. On the other hand, the mean virus titer of the carrier fingerlings which did not exhibit ascites was 10^3.6 TCID₅₀/g. The incidence of YAV in fingerlings varied by sampling periods. There was a tendency of negative correlation between the incidence of the virus and the body weight of the fingerling. These results suggest that the YAV was carried into the fish farms from offshore with the fingerlings used for the pen culture.

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A demersal fish community off Viet Nam was examined in order to know its structure in the tropics. Data were collected by a bottom trawler from December 1968 to July 1969. Analyses were made by data for three seasons from winter to summer. Quantitatively dominant fishes were lizardfish, snapper, Japanese butterfish in winter, and were snapper, lizardfish and bigeye in spring and summer. Spatially dominant fishes were lizardfish and cuttle fish in three seasons, and was bigeye in summer. These fishes are supposed to be core fishes of recurrent groups. Few fishes coexisted with others through the three seasons. Most fishes lived independently.

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This paper includes a theory and methods of determining mesh selectivity curve for a specified mesh size of codend in trawlnet from a fishing experiment with several mesh sizes. On a few assumptions, the mesh selectivity of mesh size m for fish of length l was theoretically approximated by a function of (l-l₀)/(m-m₀) in certain ranges of l and m. Here, l₀ and m₀ are constants. On the basis of the above statement, the authors derived the respective methods for determining the mesh selectivity curve from covered-net and comparative fishing experiments. In addition, this paper applied the derived methods to Margetts' data as a numerical example and discussed some problems on the methods.

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The origin of four-year-old chum salmon caught in the Bering Sea in July, 1981 was estimated from their gonad weight and scale characters. There were three different maturity groups in the gonad weight frequency distributions for both female and male chum salmon. The maturing group with lower gonad weight (MT2) had more circuli and narrower width of the first year zone of the scale than those of the immature group (MT1) and the maturing group with higher gonad weight (MT3). A comparison of the scale characters of these three groups with those of chum salmon caught in the coastal regions showed that the MT1 group was similar to U.S.S.R. and Japanese chum salmon, the MT2 group was similar to Japanese chum salmon, and the MT3 group was similar to U.S.S.R. chum salmon. This suggests that different maturity groups in the high seas catch correspond to stocks from different geographical regions.

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An attempt was made to know whether fish waste lipid treated with mold can be utilized as a feed oil or not. The lipid from mackerel waste juice was treated with Aspergillus terreus for 18 h and the treated lipid was added into a diet containing white fish meal, and the effect of treated lipid on growth of red sea bream Chrysophrys major and feed efficiency was compared with that of nontreated lipid and pollack liver oil. Treatment with the mold decreased POV and TBA value of lipid (NTL) from waste juice and increased ω3 HUFA content. The growth and feed efficiency in red sea bream fed on the treated lipid (TL) were significantly high as compared with those of fish fed on the nontreated lipid (NTL), and were similar to the fish fed on pollack liver oil (PLO).

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The present study was undertaken to investigate effect of the remaining diets on aquatic microflora in a fish culture pond using a continuous flow culture system as a model. Almost all the diets were decomposed within 10-20 days after introduction. During the first stage of the decomposition, the Vibrionaceae, Enterobacteriaceae and Pseudomonas increased rapidly, and at the second stage genus Clostridium also became a predominant component. However, these orgainsms except for Pseudomonas were replaced with mainly Acinetobacter and Moraxella after almost all the diets were decomposed and consumed. These results suggest that a certain tendency of continuous replacement of microflora exists during the decomposition of organic matter in the culture ponds.

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A study was made regarding the relationship between the toxicity and acetylcholinesterase (AChE) inhibition of three organophosphorothionates (fenitrothion, FS; diazinon, DIN; phenthoate, PAP) and three oxo-forms (fenitrooxon, FO; diazoxon, DOX; dichlorvos, DDVP) in tiger shrimp Penaeus japonicus at different larval stages. The shrimp larvae at nauplius and zoea stages showed relatively high resistance to FS, DIN and PAP, i.e., the respective 24-h LC₅₀ values were 1.84, 10.5 and 5ppm. However, the toxicity of these thiono-form phosphates increased abruptly with the progress of the larval stages, especially after metamorphosis into the postlarva, resulting in the increase by ca. 2, 600, 1, 200 and 850 times respectively to that of nauplius stage. On the other hand, the toxicity of FO and DDVP to the larvae was almost unchanged throughout these stages, at the levels of ca. 7ppb and 5.6ppm as the 24-h LC₅₀ value, respectively.
The susceptibility of the larval AChE to the tested phosphates was almost unchanged from zoea to postlarva. The concentrations of FO, DDVP, DOX, FS, PAP and DIN producing 50% inhibition (I₅₀) of the AChE activity were approx. 0.015, 0.35, 1.27, 200, 650 and 1, 200μm, respectively. Although FS showed the highest AChE inhibition among the thiono-forms; its oxon (FO) displayed 12, 000 times high AChE inhibition compared to FS. The high AChE inhibition of FO was in good correlation with its high toxicity to the larvae even at the early stage.

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A survey of Salmonella contamination of eel culture ponds was conducted in Shizuoka Prefecture. Samples were collected from an indoor culture pond (A) and an outdoor culture pond (B) in August and December, 1986. A total of 23 samples consisting of pond water, sludge, eel (skin, gill and gut contents), feed etc. were examined.
Of the 23 samples examined, 6 were found to be contaminated with salmonellae, 5 of which were collected from the pond A, and only one from the pond B. Regarding the 5 positive samples from the pond A, 3 were collected in summer, and levels of salmonellae of these samples were as follows: pond water was 7.9 cells/ml, sludge, 1.3×10⁴cells/g, and the gut contents of eels, 4.9×10² cells/g, in contrast, 2 samples collected in winter, the level of pond water was as low as 0.02 cell/ml and that of sludge was 2.7 cells/g. Only one sludge sample showing Salmonella positive from the pond B was detected in summer, and the level was 0.45 cell/g. Major serovars of the 56 Salmonella isolates were S. java (43%), S. braenderup (36%) and S. etnnessee (14%). The necessity and possibility for a Salmonella free culture and clean eels were discussed.

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About one mole of DTNB-light chain per mol of myosin was removed from rabbit myosin by heat-treatment at 30°C for 10min in a solution containing 2mM EDTA, 30mM KCl, and 20mM Tris-HCl (pH 8.5). The above treated myosin (RabM(-LC)) could bind rabbit myosin DTNB-light chain or regulatory light chains of several molluscan myosins. However, the affinity of RabM(-LC) to molluscan regulatory light chains was estimated to be approx. 1/7 times lower than that to DTNB-light chain. The binding of molluscan regulatory light chain to RabM(-LC) practically did not affected both actomyosin Mg-ATPase activity and superprecipitation activity of acto-RabM(-LC), thus conferring no Ca²⁺-sensitivity.

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We attempted here to detect new sulfur-containing feeding attractants using a method in which freshwater fish record their own strike response on a Kimographyone instrument. Among viarious sulfur-containing organic compounds, dimethyl-β-propiothetin (DMPT), and to a lesser extent, dimethylthetin, dipropyl (di)sulfide, dimethylsulfoxide and dimethylsulfone, strongly promoted the striking behavior in goldfish Carassius auratus, carp Cyprinus carpio and crucian carp Craccius auratus cuvieri when included in a synthetic diet (cellulose alone), a semi-natural diet and a natural diet. DMPT had a much greater stimulatory effect than glutamine at various concentrations. Moreover, DMPT induced much stronger neural activity in the olfactory tract of carp than L-glutamine. Thus, our results indicate that DMPT is an effective new attractant for striking of freshwater fish.

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Aggregation behaviors of human platelets and carp Cyprinus carpio, rainbow trout Salmo gairdneri, and red seabream Pagrus major thrombocytes were studied by an electronic aggregometer and microscopic observation.
Measurement was done by using electronic aggregometer. The irreversible aggregation responses were recognized in all rainbow trout and red seabream blood similar to human blood with the addition of sodium arachidonate (AA). However, the response of thrombocytes in carp blood was not induced by the addition of AA, but the reversible aggregation response was recognized in four out of twelve samples. The aggregation was not induced by the addition of sodium eicosapentaenoate (EPA) or docosahexaenoate (DHA) in fish blood like human blood. It is assumed that the differences in prostaglandin (PG) syntheses among them cause the different behaviors in the blood aggregation.
Moreover, in the microscopic observation, human platelets and all fish thrombocytes aggregated in the presence of ionophore A₂₃₁₈₇, thrombin, and collagen, but did not aggregate in the presence of EPA, DHA, PGF_2α, PGD₂, or ADP. On the other hand, in the presence of AA, PGE₂ and platelet activating factor (PAF), the aggregating responses varied among species tested.

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Sardine ordinary and dark muscle myofibrils were suspended in buffers of various pH values, stored under several conditions and examined for the remaining Ca²⁺ -ATPase activity. The ordinary muscle myofibrils showed the remaining activity maxima at pH 7 (specific activity of 0.07μmol Pi/min•mg) and 8.6 (0.10), when stored at 0°C for two days. When stored at 35°C for 30min, the ordinary myofibrils again showed the remaining activity maxima at pH 7 (0.06) and 8.6 (0.05). When freeze stored at -20°C for two days, the ordinary muscle myofirils displayed a single remaining activity maximum at pH 7.5 (0.08), and little activity below pH 6.5.
The dark muscle myofibrils showed the remaining Ca²⁺ -ATPase activity maximum at pH 6.7 (0.11μmol Pi/min•mg) when stored at 35°C, at pH 6.4 (0.14) when stored at 0°C, and at pH 7.5 (0.10) when stored at -20°C. The inactivation rate of sardine myofibrillar Ca²⁺ -ATPase activity at 30°C was slow over pH 6.8-8.6 for ordinary and at around pH 6.8 for dark muscle. These results suggest that the remaining Ca²⁺ -ATPase activity of sardine muscle myofibrils are closely related with their stability.

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A search was undertaken to find bacteria with a usefully high productivity of alginate-degrading enzyme. By an aerobic screening method, 26 bacteria with the productivity were obtained from the sea, whereas none from the freshwater and the land. The enzyme productivities of all the isolates were compared to one another. Special attention was given to the production of large quantity of the enzyme by the two strains of bacteria (strains A1-9 and A1-128). A1-9 strain produced an extracellular enzyme when grown in no alginate-adding medium. On the contrary, A1-128 strain produced the enzyme when grown in 0.3-0.5% alginate-adding medium.
The enzyme of A1-9 strain increased remarkably reducing sugar from the substrate, and that of A1-128 strain decreased the viscosity of the substrate. Both enzymes were activated by the addition of 0.3M NaCl, and showed an activity of alginate lyase.
Identification according to the Bergey's Manual of Systematic Bacteriology permitted assignment of the two strains to the genus Vibrio, and they may represent profitable sources of alginatedegrading enzyme.

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To clarify the suppressing effect of two kinds of “mirin-boshi”, which were prepared by immersing the sardine in the seasoning of “honmirin” (sweetened “sake”) or “mirinfûchômiryô” (a kind of sweetener), the volatile components of two roasted dried sardines (sample 1, 2) flavored with “honmirin” or “mirinfûchômiryô” and a roasted salt-dried sardine (sample 3) were studied. By sensory test, it was found that the fishy odor was not controlled in sample 1, but was distinctly controlled in sample 2.
The peak intensity of the volatiles identified by gas chromatography and gas chromatography-mass spectrometry in sample 3 had almost the same patterns as found in sample 1 and 2. Isobutyl alcohol, isoamyl alcohol, phenethyl alcohol and ethyl levulinate were specific components of sample 2 and the peak intensity of ethyl acetate in sample 2 was higher than that in sample 1.
Therefore the change of odor of sardine with the addition of the above five authentic compounds was examined by sensory test.
It seemed that isobutyl alcohol, phenethyl alcohol, ethyl acetate and ethyl levulinate were derived from “mirinfûchômiryô, ” which greatly contributed to mask the odor of sardine in sample 2, but isoamyl alcohol didn't play an important part to mask the fishy odor.

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Four murine hybridomas capable of producing monoclonal antibodies (MR-18, MR-21, AT-83 and AT-86) to cell surface antigens of genus Chattonella (Raphidophyceae) were developed and an indirect fluorescent antibody techinque was used to test reactivity of the antibodies against various strains of genus Chattonella.
According to the reactivity with the monoclonal antibodies, the 19 strains of genus Chattonella could be divided into 5 groups (Type I-V). Seven strains, which were morphologically identified as C. marina, were divided into 2 groups, 5 strains of Type I, and 2 strains of Types II. Similarly, 10 strains of C. antiqua were divided into 2 groups, 2 strains of Type III, and 8 strains of Type IV. In addition, it became clear that one of two strains that had not been identified yet belonged to Type III, and another strain which did not react with any of these 4 monoclonal antibodies. This suggests that the latter may belong to another group Type V.
Furthermore, we tried to apply the antibodies to the field samples obtained from natural sea water. C. antiqua Type III was detected from the bloom occurring offshore Buzen in August, 1987 and C. antiqua Type III and IV were detected from the bloom occurring offshore Akashi in August, 1987.

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Myosin subfragment-l (S-1) of carp was incubated at 30°C in a medium consisting of 0.5M KCl, 20mM Tris-HCl (pH 7.5) and the Ca-ATPase activity and turbidity change were followed. The turbidity of carp S-1 increased as Ca-ATPase activity decreased. Upon centrifugation of thus turbid S-1 solution, the insoluble fraction was obtained as the pellet, and was analyzed by SDS-gel electrophoresis. The turbid component of S-1 was proved to be S-1 heavy chain aggregates dissociating light chains. The elution profile of mildly heated carp S-1 on Sepharose CL-4B gel filtration showed an accumulation of S-1 oligomer, not dimer, which is an intermediate of the turbid form of the S-1 heavy chain aggregates.
These results indicated that the formation of heavy chain aggregates caused the increase in the turbidity of S-1 solution which was accompanied by light chain release. Such denaturations of S-1 as above were found to be delayed in the case of rabbit S-1.

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Bacterial flora and viable counts in the gills and the digestive tracts (stomach and intestine) of mudskipper fishes Boleophthalmus pectinirostris and Periophthalmus cantonensis and in mud of a mud flat were studied to discuss the primary factors which control the composition of bacterial flora in the digestive tracts.
The flora was composed principally of Vibrio, coryneforms and others in the mud and the gills, and of Vibrio or coryneforms in the digestive tracts. The composition of flora in the stomach was similar to that in the intestine for P. cantonensis but not for B. pectinirostris. The counts in the stomach were much lower than that in the intestine for B. pectinirostris but could not recognize obvious difference between the two for P. cantonensis. The counts in the intestines of both the fishes were much higher in aerobic incubation than in anaerobic incubation and a large part of bacteria counted in aerobic incubation was Vibrio. The maximum count was in 100% sea water medium in the mud but in 50% sea water medium in the intestines, and a large part of bacteria accounted in both the samples was Vibrio. The counts in the digestive tracts were lower in autumn than in spring and summer in case of B. pectinirostris but almost equal for all seasons in case of P.cantonensis.
From these facts it was presummed that the flora of the digestive tracts is influenced by bacteria from the mud, differing from the stage of progress of the stomach and from wintering season in the fishes, being controlled by salt concentration and oxygen tention of sea water to be supplied through “water-drinking” for osmoregulation.

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