The distribution and movement of the hairtail Trichiurus lepturus stock in the Aru Sea were investigated using logbook data from four Taiwanese commercial otter trawlers. Fluctuations in population size, population density index and the distribution of catch per unit effort (CPUE) and fishing effort are discussed. The CPUE data were standardized by using the generalized linear model (GLM) in which fishing month, fishing area and size category of the hairtail were taken into account. The fishing season could be divided into three episodes: aggregation between March and April, dispersion between May and June, and aggregation again between July and December. A seasonal two-peak distribution of the population size of hairtail reflects the aggregation-dispersion pattern. The first peak in May-June can be explained in terms of the hairtails' overwintering migration. The second peak in October-December is likely to be the result of spawning aggregation.

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Aoshio is hypoxic milky blue-green seawater observed in some eutrophic bays. Previous studies have shown that colloidal sulfur causes the coloration and that the source of aoshio water is attributed to coastal anoxic bottom water. Occurrences of aoshio have been reported in limited areas of coastal seawater, although hypoxic transparent water seems rather universal. Promotion in auto-oxidation of sulfide by metal ions in seawater was investigated to explain the occurrences of aoshio. Artificial seawater containing 10 μM metal ion was assayed for the sulfide oxidation rate. The velocity constant which represents the oxidation rate within the initial 30 min and the amount of reacted sulfide in 2 h were determined by oxygen monitoring and sulfide quantification, respectively. Fe²⁺ and Cu²⁺ enhanced the initial 30 min reaction. Fe²⁺, Fe³⁺ and Ni²⁺ increased the amount of reacted sulfide in 2 h, forming whitish turbid water. Seawater from a suspected source of aoshio water was also assayed for the auto-oxidation rate of sulfide. The oxidation rate in water from 12 m depth was 13-19 times higher than the artificial seawater without an addition of heavy metal ions. More than 15% of the oxidation rate in 12 m deep seawater was explained by dissolved iron in the seawater.

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The survival of Japanese whiting Sillago japonica and by-catch species captured by a sweeping trammel net was examined to assess the effects of differing species, captured conditions, and body lengths on survival, in Tateyama Bay, Chiba Prefecture, Japan. All the live samples were kept in laboratory tanks for 4 days of successive survival observation. The survival ratio of the Japanese whiting varied by the captured conditions. The fish captured by pocketed condition was 27% surviving at the fourth day, which was significantly higher than the gilled and entangled fish. Most of the by-catch species survived for 4 days. About 60% of dead Japanese whiting were observed to have scar injury and damage on the body surface. For the by-catch species, the body damage occurred only in stripedfin goatfish Upeneus bensasi, Temminck's surfperch Ditrema temmincki, and tidepool gunnel Pholis nebulosa. Therefore, it suggests that the conservation measure through catch-and-release may be an appropriate method for most by-catch species, but not for the Japanese whiting.

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The genetic structure of the samples of Mustelus manazo between central Japan and Taiwan was investigated by starch gel electrophoresis. From a total of 20 enzyme loci scored, only two of them (CK-A and sSOD-1) showed polymorphism with sufficient allelic variation that would be useful for analysis of population structure. The Taiwanese samples have unique allele of CK-A 52 and sSOD-1 40 that are absent in the Japanese samples. Mean heterozygosity values were 0.027 and 0.055 for two Taiwanese samples and 0.008 and 0.013 for two Japanese samples. The chisquare analysis shows significant differences (P < 0.001) between the pooled central Japanese samples and Taiwanese samples indicating that they are two separate populations with moderate divergence (F_ST=0.063). A possible explanation of population divergence between the two countries is also discussed.

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In order to know how fish use temporary streams, we set up artificial temporary streams with and without shelters and investigated the fish that colonized there from connected permanent streams. A total of 220 fish belonging to six species were captured over four sampling periods from May to September, with Japanese dace Tribolodon hakonensis being the most abundant (75%). More Japanese dace colonized the stream with shelters than without shelters. The standard length and condition of Japanese dace tended to be greater in the stream with shelters than without shelters. Foraging behavior and area of Japanese dace differed significantly between the two streams; more Japanese dace employing drift feeding near the entrance of the shelterless stream. Japanese dace predominantly fed upon chironomid larvae, which became abundant in stream mud in July. However, in August and September, Japanese dace rarely preyed upon chironomid larvae and their digestive canal fullness was low, probably because most chironomid larvae had been consumed. This tendency was more prominent in the stream with shelters. The use of temporary waters by Japanese dace changed dynamically in response to the abundance of chironomid larvae and the presence or absence of shelters.

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This study was conducted to determine the dietary protein requirement for the growth of juvenile Manchurian trout Brachymystax lenok. Three replicate groups of fish weighing 3.44 g were fed the five isocaloric diets containing various protein levels from 29% to 57% for 10 weeks. White fish meal was used as the sole protein source. Weight gain and feed efficiency of fish improved with increasing dietary protein level up to 43% and 49%, respectively, and reached a plateau above these levels. Dietary protein requirement using a broken-line model was estimated at 43.6% for weight gain of the fish. The protein efficiency ratio tended to decrease with increasing dietary protein level, but there was no significant difference among the diets containing 29%, 35% and 43% protein levels (P > 0.05). The protein content of fish fed the 29% protein diet was significantly lower than that of fish fed the 57% protein diet (P < 0.05). However, moisture, lipid and ash contents of fish were not significantly affected by dietary protein level (P > 0.05). These findings indicate that 43-44% dietary protein level with 10% lipid and 19.2 MJ gross energy/kg diet could be recommended for the optimum growth and efficient protein utilization of juvenile Manchurian trout.

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An inhibitory effect of Kunitz and Bowman-Birk soybean trypsin inhibitors (K- and BB-SBTI) was investigated on tryptic and chymotryptic proteinases of a brood of tiger puffer Takifugu rubripes and yellowtail Seriola quinqueradiata. These assist to comprehend the differences in dietary soybean meal (SBM) utility by fish species and to develop low cost SBM diets with low contents of fish meal. The K-SBTI strongly inhibited tryptic proteinase and weakly inhibited chymotryptic proteinase from the hepatopancreas and intestine including pyloric ceca of the fishes. The BB-SBTI strongly inhibited both proteinases of the fishes. The K-SBTI inhibition for tryptic protease and the BB-SBTI inhibition for tryptic and chymotryptic proteases were relatively constant in tiger puffer with growth of 12-199 g bodyweight. In yellowtail with growth of 7-672 g bodyweight, the K-SBTI inhibition for tryptic protease and the BB-SBTI inhibition for chymotryptic protease were also relatively constant. The BB-SBTI inhibition for yellowtail tryptic protease typically fell in the stage from 7 g to 57 g bodyweight, and then decreased slightly or was maintained constantly. These results indicate that there are different inhibitory modes of K- and BB-SBTI and there is inter- and intraspecific diversity of tryptic protease conformation between the two species.

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The aim of this study was to investigate the cause of green liver in red sea bream fed substitute protein diets. Red sea bream Pagrus major was given either of the following diets for 28 weeks: (1) control diet (50% fish meal), (2) low level fish meal diet (15% fish meal), and (3) non-fish meal diet (0% fish meal). The green liver was observed in all groups tested, but the incidence was much higher in the experimental diet groups. The feeding of substitute protein diets reduced plasma triglyceride and cholesterol levels. However, there was no significant difference in plasma hepatic enzyme activities and plasma bile salts concentration among the treatments. Fish fed the substitute protein diets showed low hepatic taurine levels with an appearance of a biliverdin in the liver. Moreover, the proportion of ditaurobilirubin to total biliary bile pigments was significantly lower in fish fed the substitute protein diets. These data indicate that feeding of substitute protein diets did not induce any cholestatic hepatobiliary obstructions and that the low hepatic taurine level was one of the probable factors responsible for the occurrence of green liver in red sea bream fed substitute protein diets.

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The effectiveness of in vitro embryo culture of the giant freshwater prawn Macrobrachium rosenbergii depended on the age of the embryos at the onset of culture and on the concentrations of various compositions in the medium. Embryos that started being cultured on day 0.5 after oviposition were more sensitive to variations in the medium compositions than those that started being cultured on day 10.5 after oviposition. An optimal NaCl level was essential for embryonic development, survival, hatching and survival of the newly hatched larvae. Variations of NaCl or KCl levels dramatically altered embryonic development, and variation of the MgCl₂+MgSO₄ level significantly lowered survival of the embryos that started being cultured at the early stage of development. In contrast, no significant change in embryonic development was observed upon variation of the CaCl₂ level. Hatching of the embryos required the presence of NaCl and CaCl₂ but not KCl or MgCl₂+MgSO₄. The ionic requirements of the newly hatched larvae differed from that of the developing embryos. Variations of NaCl, KCl or CaCl₂ but not MgCl₂+MgSO₄ levels significantly influenced the survival of the newly hatched larvae.

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Stock enhancement is used in Japan as a tool to help the replenishment of wild populations of red sea bream Pagrus major. In this study, we analyzed the genetic diversity and composition of wild red sea bream at seven locations around Shikoku Island, South-west Japan, using three microsatellite loci. This analysis was done to test the hypothesis that: (i) red sea bream comprises a single Mendelian population along Japan; and (ii) stock enhancement programs around Shikoku Island are causing genetic differentiation among wild stocks. The results indicated that some locations from the Shikoku area were not significantly different from the rest of Japan, supporting the hypothesis of a single Mendelian population. Significant departures from Hardy-Weinberg equilibrium and significant pairwise F_ST among locations indicated genetic instability within this region. We suggest that the stock enhancement programs made in the region are the possible cause of this genetic instability. A management scheme for the hatcheries involved in the stock enhancement of red sea bream is presented.

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Polyamines are widely distributed in nature and known to have many roles in living organisms. We investigated the concentrations of polyamines together with inorganic nutrients during a summer bloom period in the Seto Inland Sea of Japan. Putrescine and spermidine were the major polyamines in the coastal seawater. The concentrations at 1 m depth varied widely during the sampling period and ranged from 2.0 to 32.6 nM and 1.0 to 14.1 nM. Spermine concentrations were much lower than putrescine and spermidine. In addition, other polyamines (diaminopropane, cadaverine, norspermidine, homospermidine, norspermine) were also detected. Putrescine and spermidine seemed to be significant compounds in dissolved organic nitrogen in coastal seawater.

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For design or improvement of fishing nets, a model test based on Tauti's law or Froude's law is well executed. However, because these modeling rules are based on the proportion of the drag of the net to the square of water velocity, the converted drag of the net from the result of model testing is considerably large compared with the observed value. In this study, Tauti's law and Froude's law were corrected considering the drag coefficient of the net to the Reynolds number based on the twine diameter used experimentally. Three different scale models: 1/12, 1/20 and 1/50 of a midwater trawl net of 61 m in total length were made according to the modified Tauti's law and Froude's law, and the full-scale and model experiment were carried out. Consequently, the difference between the converted drags of full-scale by three scale models and measured values was within 10%. Each of these modified modeling rules is effective for the model test of trawl nets.

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This is another report from a series of studies aimed at determining the energy and protein requirements based on the optimum feeding frequency of yellowtail during the winter season. Experiments were conducted at Mie and Oita Prefectures, Japan, employing extruded pellets of known digestible energy (DE) and digestible protein (DP) values. Four groups of fish were fed at frequencies of five, three, two, and one time(s) per week. The most efficient feed performance was obtained for the feeding frequenecy of three times per week. The DE and DP requirements calculated based on the feeding rate at this frequency were 38.7 kcal and 2.8 g/kgBW per day (14.3-17.3°C) in Mie and 30.4 kcal and 2.2 g/kgBW per day (13.8-17.5°C) in Oita, respectively. The present results and the observations on the changes of the contents in digestive tracts tallied with our previous work, confirming that the optimum feeding frequency was three times per week.

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The effect of different dosages of vitamin K, either as phylloquinone or menadione sodium bisulfite (MSB), on vertebrae formation during growth of mummichog Fundulus heteroclitus was investigated. Diets without vitamin K caused a significantly higher incidence of bone deformity in fish than diets supplemented with MSB or phylloquinone (P < 0.01). These results indicate that vitamin K is essential for mummichog. A massive dose of MSB caused a high incidence of bone deformity compared with a lower dose, while an increased dose of phylloquinone brought about no significant difference in deformity incidence. The vertebral deformity was significantly higher (P < 0.01) in fish fed a vitamin K-free diet (Control Group) and MSB-supplemented diet (Group MSB25) compared to fish fed a phylloquinone-supplemented diet (Group PK1). These results indicate that phylloquinone is more suitable than MSB as a vitamin K source in fish feed.

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Flume-tank experiments were performed to examine the depth response of a new type of depth-controlled gillnet. Variations of net depth were investigated as the warp was paid out and wound up for different changes of warp length, main sinker weights, and winch speeds. In most experiments, when the warp finished paying out, the net continued to descend and then ascended slightly to an equilibrium depth (overshoot phenomenon). The overshoot distance was nearly constant when the warp was wound up and increased linearly with increasing winch speed when the warp was paid out. An increase in winch speed reduced net settling time, which converged on a constant value for both paying out and winding up.

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We determined the complete nucleotide sequence of the mitochondrial genome for the Japanese eel Anguilla japonica (Teleostei: Anguilliformes). The entire genome was purified by gene amplification using a long polymerase chain reaction (PCR) technique, and the products were subsequently used as templates for PCR with 60 fish-versatile and six species-specific primers that amplify contiguous, overlapping segments of the entire genome. Direct sequencing of the PCR products demonstrated that the genome [16 685 base pairs (bp)] contained the same 37 mitochondrial genes (two ribosomal RNA, 22 transfer RNA and 13 protein-coding genes) as found in other vertebrates, with the gene order identical to that in typical vertebrates. A major non-coding region between the tRNA^Pro and tRNA^Phe genes (967 bp) was considered as the control region (D-loop), as it has several conservative blocks characteristic to this region.

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This paper evaluates the stocking effectiveness of masu salmon Oncorhynchus masou in Hokkaido, northern Japan, through a coast-wide two-stage sampling survey of commercial landings. From January to June 1994-1996, commercial landings of masu salmon at 33-36 fish markets were sampled at 7-10 days intervals, and 60 866-72 124 fish were examined for marks indicated by fin clips. Based on the survey data, numbers of total and hatchery-reared masu salmon landed were estimated. To examine the structure of the errors, stratification of fish markets was implemented on the basis of geography and magnitudes of landings, and the stratification improved accuracy and precision of the estimates. Accuracy of the estimated numbers of total fish was evaluated by being compared to the true numbers of masu salmon landings reported by fishermen's cooperative associations. Estimates of total masu salmon landings were within ± 10% of the true numbers. The estimated recovery rates (± SE) for hatchery-reared masu salmon smolts were variable ranging from 0.18 (± 0.06) to 3.50 (± 0.41)% among the stocked groups. An optimal sampling strategy was examined to obtain precise estimates for future studies.

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The relationship between mean weights of hatchery-reared masu salmon Oncorhynchus masou smolts at release and the subsequent recovery rates by coastal commercial fisheries in Hokkaido, northern Japan, was investigated using the maximum likelihood method. A strongly positive correlation was observed, showing smolts with a mean of 32.6 g obtained an approximately 20-fold recovery rate of those with a mean of 14.8 g. The model with log-transformed independent variable (Y_i=-11.237 + 4.239 ln X_i) was selected as the most parsimonious model to represent the release size (X_i) and recovery rate (Y_i) relationship.

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Eight thermotolerant, ethanol-producing yeast strains were isolated from hot spring drainage at Rendaiji in Shizuoka Prefecture. The tolerance to elevated temperatures of three strains (RND13, 14 and 17) was studied in comparison with that of mesophilic yeasts. All three grew on a liquid culture at temperatures up to 42-45°C, with maximum growth rates at 37°C or 35°C, whereas the upper limit temperatures for fermentation were higher, ranging from 48 to 55°C. Above all, RND13 had higher ethanol productivity of 72.1% at 40°C for 24 h than that of 57.0% obtained by brewers' yeast at 25°C for 120 h. Regarding the taxonomy of RND13, 14, and 17, they were found to be Torulaspora delbrueckii, Dekkera sp., and Candida albicans, respectively. This is the first report on yeasts capable of fermentation over 51°C, as well as on the isolation of yeasts from a hydrosphere with elevated temperatures.

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The seasonal changes in levels of chemical constituents in the muscle and viscera of small abalone Haliotis diversicolor fed gracilar and an artificial diet were investigated. Muscle yields were higher in winter and spring. In October specimens, total adenosine 5'-triphosphate (ATP)-related compounds (ARC), total free amino acids (FAA), and glycogen in both muscle and viscera decreased markedly. The artificial diet fed to small abalone had much higher glycogen in the muscle than those fed on gracilar, and showed a great seasonal change. Total amounts of ARC in the muscles were higher through March to July, while those in the viscera were maximal in January. Taurine, arginine, glycine, glutamic acid, and alanine were the major FAA in both tissues, accounting for 81-94% of the total FAA. Total amounts of FAA in the muscles were higher in the samples collected from winter and early spring than in other seasons. Glycine, glutamic acid, and adenosine monophosphate might be the most important taste components related to the palatability of small abalone. Their total amounts in the muscles of the two specimens were considerably high in December to March. This finding suggested that small abalone produced in winter and early spring might be more palatable.

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An experiment was carried out to investigate the effect of an intraperitoneal glucagon administration (60 μg/kg) on enzyme activities and metabolic intermediate concentrations in the hepatopancreas and muscle of common carp Cyprinus carpio. In the hepatopancreas, glycogen phosphorylase a activity together with cyclic adenosine-5'-monophosphate (AMP) concentration were significantly increased, and glycogen content was significantly decreased, at 1 h after the glucagon administration. Additionally, glucose-6-phosphatase and fructose-1, 6-bisphosphatase activities as well as plasma glucose and free amino acid concentrations were increased after its administration. In the muscle, glucose and glycogen contents increased after the administration. Furthermore, the hormone administration also increased phosphofructokinase activity together with fructose-6-phosphate, AMP, and adenosine-5'-diphosphate concentrations and decreased adenosine-5'-triphosphate concentration. From 3 h after the administration, many parameter concentrations in both tissues showed a tendency to recover to the initial levels. These results suggest that glucagon administration enhanced glycogenolysis and gluconeogenesis in the hepatopancreas, and as a consequence, glucose was released into the bloodstream. The blood glucose seems to be metabolized through enhanced glycolysis and glycogenesis in the muscle.

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Six peptides (grammistins Pp 1, 2a, 2b, 3, 4a and 4b) with both hemolytic and ichthyotoxic activities were isolated from the skin secretion of the soapfish Pogonoperca punctata by gel filtration and reverse-phase high performance liquid chromatography. They were completely sequenced and found to be simple peptides differing from the previous suggestion that they are peculiar peptides with tertiary amine or quaternary ammonium base moieties. Grammistins Pp 1, 2a and 2b were composed of 13 residues, Pp 3 of 25 residues and Pp 4a and 4b of 24 residues. While grammistins Pp 4a and 4b were identical and highly homologous with grammistin Gs 2 previously isolated from another soapfish Grammistes sexlineatus, the other grammistins did not have homologies with any proteinic or peptidic toxins known to date. Judging from circular dichroism data, helical wheel projections and hydrophobic moment plots, all the isolated grammistins are surface-seeking peptides with an abundance in amphiphilic α-helicity, similar to pardaxins from the skin secretion of two species of soles and melittin from bee venom as well as the G. sexlineatus grammistins.

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