This study investigated various aspects of the reproduction of Liza macrolepis and its estuarine utilization in Kaohsiung River and the harbor area. Among ca. 2100 samples collected between February 1992 and June 1996, one hermaphrodite (fork length=22.0cm) was found. The sizes of 50% sexually mature females and males were estimated as 17.0-17.8cm and 16.1-16.7cm in fork length, respectively. The standard fecundity was 6.48±2.82×10³. The relationship between absolute fecundity (AF) and fork length (FL) was expressed as AF=0.00891 FL^2.349. Spawning of L. macrolepis occurred between December and May, and is related to the decreases in sunshine hours, in precipitation and in temperature. The nearshore waters are the spawning grounds of the fish, where spent and mature fish aggregate. The species is a total spawner. One-to-two-months-old fish (1-2cm fork length) probably enter the inner harbor area for its abundant food supply. More females than males move into the inner estuary in the pre-spawning period, and then the fish undertake a seaward spawning migration to the nearshore areas in the spawning season. However, males gather in a greater number than females on the spawning ground during the spawning season. The estuary is a very important feeding ground for juvenile, pre-spawning and post-spawning females L. macrolepis. Our results also indicate a geographic differences in the reproductive characteristics of L. macrolepis.

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A substantial number of a lanternfish, Stenobrachius leucopsarus (Myctophidae), were collected by mid water trawls at night in the near-surface layer of the Bering Sea in the summer of 1994. Size composition, age, growth, and food habits were examined for the eastern, northern, and western areas of the Aleutian Basin. Standard length ranged between 22 and 106mm with modes at 60, 72, and 74mm in the eastern, northern, and western areas, respectively. Age was determined for 181 individuals by using ground otoliths and no geographical difference in length at age was observed. The growth was expressed by von Bertalanffy's equation as:
Lt=106.2×{1-e^{-0.265×(t-0.432)}},
where Lt is standard length in mm and t is age in years with an assumption that the fish were born in February. S. leucopsarus fed mainly on copepods, euphausiids, ostracods, and amphipods in the nearsurface layer.

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Scientific data collected by Japanese tuna longline research and training vessels during 1967-1970 and 1992-1995 were used for analyses of the historical change in species composition of pelagic sharks and CPUE by species between the two periods in the four areas into which the area 0°-20°N & 140°E-140°W in the Pacific Ocean were divided equally. To examine the long-term change of shark abundance, CPUE for sharks combined (total shark) was also analyzed from 1973 to 1993 which covered the majority of the missing period between the two periods. Blue shark Prionace glauca was the dominant species in these areas and the shark species composition in number changed somewhat in these areas between the two periods. Nominal CPUE of oceanic whitetip shark Carcharhinus longimanus and silky shark Carcharhinus falciformis decreased in three areas and that of thresher sharks Alopias spp. increased in all areas. However, levels of the CPUE adjusted with the effect of gear type did not change remarkably between the two periods. CPUE of total shark did not indicate any tendency in these areas from 1973 to 1993. Considering that there was no appreciable change in abundance of blue shark between the two periods or of total shark in the interim period between 1973 and 1993, the abundance of blue shark were inferred not to have changed significantly in these areas from 1968 to 1995.

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The genetic structure of red sea bream population Pagrus major, was assessed from fish collected at eight locations along Japan, China and the Southwest Pacific. Genetic diversity and population subdivision was estimated based on microsatellite DNA analysis. The results obtained with three microsatellite loci showed a high genetic diversity for Japan and China locations with mean number of alleles per locus between 21 to 30, and mean observed heterozygosities ranging from 0.804 to 0.867. Southwestern Pacific samples showed intermediate genetic diversity, with mean values of 14 alleles per locus and an observed heterozygosity of 0.7. Significant pairwise F_ST and R_ST values were observed between locations showing that the red sea bream population is structured both in the North and Southwest Pacific. According to a hierarchical Analysis of Molecular Variance (AMOVA) performed among groups of locations, three populations are proposed: Australia, New Zealand and Japan-China. Moreover, a division into three subpopulations is proposed for the Japan and China region. One located in the South China Sea, one more in the area covered by the East China Sea, Southwest Japan and Japan Sea, and the last one along the Pacific coast of Japan. The importance of considering these findings for design of management strategies of both the commercial fishery and stock enhancement programs is addressed.

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A marking method for Kuruma prawn Penaeus japonicus, through recovery of the colored pigment area in uropods, was developed. The method was tested by cutting the uropods of 75 prawns ranging from 21 to 73mm in body length (BL) in the laboratory and 3, 733 prawns from 35 to 75mm in BL in the sea off Kyoto Prefecture.
After cutting uropods, the recolored pigment area was visibly reduced though uropods length regrew nearly equal to that of uncut uropods. The degree of pigment reduction increased with the increase in the BL of prawn used, and a 50% reduction in comparison with uncut uropods occurred for 60mm in BL. As it was suggested that a 30% reduction of the colored pigment area could be detected by the naked eye as marks, this method is suitable for prawns larger than 30mm in BL. The effective location of cutting uropods was just below the protopodite with no severe effects on survival and growth of marked prawns. From the test in the sea, the method proved successful for application as a long-lasting mark to a large field sample of prawns.

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An artificial seawater containing acetate, at the concentration of 100μg/ml, was infiltrated through a seashore sediment column in an acrylic pipe, which was 30cm in length and 3.6cm in diameter. Acetate concentrations in the effluent remained around zero until the filtration of 125ml of seawater, and then began to quickly increase to 83.5μg/ml after the filtration of 200ml. The level in the effluents, thereafter, reached the acetate concentration of the influent after a gradual increase. Total amount of acetate removed from the seawater was calculated as 10.9mg, by integrating the difference in the concentration between the effluent and the influent. Autoclaving did not affect the amount of acetate removed. Hence biological activities should play only a limited role in the scavenging of acetate upon the percolation through sediment. It is suggested that non biological process plays an important role in diagenesis of organic materials in seashore sediments.

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Interspecific relationships between ayu Plecoglossus altivelis and Japanese dace Tribolodon hakonensis were investigated experimentally in a semi-natural water course. Both species attacked conspecifics in territorial defense or dominance-subordination relationships. When both species encountered, ayu occasionally attacked Japanese dace, but were not attacked. Ayu fed predominantly upon algae on cobbles and their feeding activities were not affected by Japanese dace. Japanese dace were omnivorous, feeding upon both algae and terrestrial and aquatic invertebrates, but did not feed upon algae when ayu were present. On this occasion, Japanese dace predominantly used the area near the stream banks where ayu were not present. The growth rate of Japanese dace was not affected by ayu as a result of resouce partitioning between the two species, whereas ayu growth was facilitated when they coexisted with Japanese dace, probably because Japanese dace increased the algal standing crop by decreasing the number of aquatic invertebrates.

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Growth bands of the colonies of the scleractinian coral Porites collected at Okinawan coral reefs were counted on Soft-X Ray micrographs, and age and growth rates of infaunal non-boring organisms were estimated indirectly from the annual coral-growth rings of the host coral. The organisms include a calcareous-tube polychaete Spirobranchus corniculatus (Grube), a sand-tube sabellariid polychaete, Idanthyrsus sp., a vermetid gastropod Dendropoma maxima Sowerby, a pecten bivalve Pedum spondyloideum Gmelin, and a coral barnacle Cantellius sp. The three tubicolous former species showed growth in various directions, and 15 to 20 years (S. corniculatus), 8 years (Idanthyrsus sp.), and 15 years (D. maxima) longevity were reliable estimates in this study. In contrast, the pecten bivalve and the coral barnacle showed lesser longevities, usually less than 7 years, and they grew vertically in almost the same direction as the host coral; thus, their growth rates can be estimated roughly by shell or slit-like hole length in relation to average host coral growth. We present here a new and practical method to estimate age and longevity of non-boring coral infauna, and we discuss marine organism growth and longevity with emphasis on polychaetes.

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In this study, regional and short-term changes in microbial biomass and community structure in mariculture and non-mariculture areas were studied using phospholipid ester-linked fatty acid (PLFA) analysis. Sediment samples were collected fortnightly from fish farms of Japanese flounder, and yellowtail, and ambient area (200m away from these fish culture areas), coastal and oyster culture areas in Hiroshima Bay. The samples were analyzed for sediment parameters, lipid-bound phosphate, and biomarker fatty acids. Microbial biomass, as indicated by lipid-bound phosphate gradually increased in fish culture areas while intermittent increases were observed in other areas. Levels of lipid-bound phosphate in sediments were in the following order: oyster<ambient<flounder<coastal<yellowtail.Results of principal component analysis of PLFA composition revealed short-term changes in microbial community structure occurring in the study area. Marked changes in the composition of microbial communities were observed in fish culture impacted sediments with increased proportions of the group including sulfate reducing bacteria. In ambient and oyster areas, no such changes in the composition of microbial groups were evident. Microorganisms in sediments may be subjected to stress due to the highly reduced condition of the sediments and high levels of acid volatile sulphide.

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Sequence analysis on the mitochondrial DNA control region was conducted for seven samples of amphidromous ayu Plecoglossus altivelis, six from the Japanese Archipelago and one from the Korean Peninsula, to understand their genetic variation and geographic population structure. The larger extent of net nucleotide substitution between Korean and Japanese samples, shown by intrasample clustering of the Korean samples in neighbor-joining phylogram, indicated that the Korean sample represented a genetically distinct population. Within the Japanese Archipelago, intrasample nucleotide diversities were high and masked intersample nucleotide divergences, with no obvious correspondence between genetic (net nucleotide substitution) and geographical distances. This may imply that at the mitochondrial DNA level there was no genetic differentiation among samples and they belonged to a single large population. However, minute but significant heterogeneities in the degree of intrasample nucleotide diversity and the frequency of nucleotide substitution at specific sites among Japanese Archipelago samples suggests the population is substructured as a metapopulation.

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To investigate the early life history of Japanese Spanish mackerel Scomberomorus niphonius in the Seto Inland Sea, abundance, occurrence, feeding habits, and growth of larvae were examined from wild specimens collected in Hiuchi-nada in 1995 and 1996. In addition, Japanese Spanish mackerel were reared in the laboratory to determine the rate of otolith microstructual increment formation during early stages.
Japanese Spanish mackerel in the central waters of the Seto Inland Sea appear to have evolved a reproductive strategy of short-term spawning timed to correspond to the seasonal-peak abundance of their prey. Japanese Spanish mackerel laevae were almost exclusively piscivorous and their most important prey was Clupeiformes larvae with slender body form. Occurrence of Japanese Spanish mackerel eggs and larvae was restricted with a peak abundance in late May to early June, corresponding with a peak abundance of Clupeiformes larvae. Age estimation for 70 wild larvae and early juveniles revealed a mean growth rate of 1.03mm/day between 4 and 20 days after hatching, which appears to be markedly higher than those from most of coastal marine fishes.

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Age and growth of the black rockfish Sebastes inermis off Miura Peninsula in central Japan were estimated from otoliths of 359 fish. Most of otoliths had a translucent margin from April to September and an opaque margin from October to May. The translucent zone was formed once a year and hence it can be used as an annulus. Growth of S. inermis was expressed by von Bertalanffy growth equation as L_t=211.5[1-exp{-0.277(t+0.991)} for males and L_t=282.2[1-exp{-0.166(t+1.291)}] for females, where L_t is standard length in mm and t is age in years. The maximum age in the sample was 6 years old for males and 7 years old for females. At ages up to 3 years old there was little difference in length by sex, but females over 3 years old grew faster than males.

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The histological examination of the spleen of Japanese conger Conger myriaster revealed that there were many eosinophilic island-like structures in splenic hematopoietic tissues, which consisted of large square cells and fibrous structure, when stained with hematoxylin and eosin. Silver stain showed these fibrous structures were composed of abundant reticular fibers that occasionally formed lattice structures. Electron microscopically, these structures consisted of cuboidal endothelial cells, reticular cells, and reticular fibers. In neighboring tissues, there were abundant thrombocytes, lymphoid cells, and macrophages (or monocytes). Basement membranes were poorly developed. When carbon suspensions were injected into the aortic bulb, carbon particles were ingested by macrophages and/or reticular cells in the islands, and were also observed on the bundles of reticular fibers. These data indicate that the eosinophilic island-like structures observed in Japanese conger spleens are well developed splenic ellipsoids, and suggest that such tissues provide a good model for the investigation of trapping foreign antigenic and non-antigenic substances in fish.

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We examined effect of aquatic hyperoxia on respiration of yellowtails exposed to Chattonella marina and measured relevant physiological parameters of the fish during the exposure. Water O₂ saturation level was elevated from 100% to 300% when arterial Po₂ (Pao₂) was found to have declined below 30mmHg during the exposure. In the first experiment (experiment 1, N=7), Chattonella exposure lasted 210 min, followed by a recovery period of 210 min in normoxic water free of Chattonella cells. In the second experiment (experiment 2, N=7), Chattonella exposure lasted 420min in hyperoxia. Survival rates of yellowtail of the two experiments were 100% and ca. 60% (four fish survived, three fish died) in experiment 1 and 2, respectively. In both experiments, hyperoxia failed to elicit expected large increases in Pao₂, which suggests that resistance to diffusion of oxygen through the respiratory epithelium was increased by the presence of Chattonella cells. Ventilatory pressure (VP) was consistently enhanced when Pao₂ was initially depressed in normoxia, but such stimulation of VP did not always occur during hyperoxia even though Pao₂ was often depressed under this condition. The gill showed variable degrees of lesions.

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Ontogeny of thyroid and interrenal systems were examined in laboratory-reared and wild Japanese sea bass Lateolabrax japonicus.
In laboratory-reared fish, concentrations of 3, 5, 3'-triiodothyronine (T₃) several times higher than thyroxine (T₄) were found in newly hatched larvae. Both T₄ and T₃ decreased to low levels during yolk absorption. T₄ concentration started to increase coinciding with the first appearance of thyroid follicles. In contrast, T₃ did not increase until transformation stage. Transient increases were observed in both T₄ and T₃ during transformation and early juvenile stages. Cortisol concentration was close to non-detectable level at hatching but started increasing before the completion of yolk absorption and also before the first appearance of interrenal cells examined by histological sections. A transient increase in cortisol concentration was found during larval period, followed by a decrease at transformation and early juvenile stages, suggesting specific role (s) of cortisol during the larval period in Japanese sea bass.
Wild sea bass were caught in Chikugo river estuary, Ariake Sea. Since wild sea bass at transformation and early juvenile stages showed T₄ and T₃ concentrations similar to those of laboratory-reared fish, thyroid hormones are considered to be controlled mainly in a developmentally-programmed manner, not in an environment-related manner, suggesting an involvement of thyroid hormones in events occurring during the early life history of sea bass. Probably because of the stress induced by sampling pressure, cortisol concentration in wild sea bass was 10 to 30 times higher than that of laboratoryreared fish. However, the fish caught at the uppermost freshwater station showed as low cortisol concentrtion as in laboratory-reared fish.

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The annual reproductive cycle of a small flounder (aramegarei), Tarphops oligolepis, was examined in Wakasa Bay from the appearance of recently settled juveniles in the field and the female maturity during a year. Seasonal changes in the distribution of standard length indicated the presence of two spawning periods, July and October, when small juveniles appeared in the nursery ground. In females, gonadsomatic index (GSI) showed a peak (10.8) in spring, decreased to a low level in September (1.1), increased again to form another peak in November (8.3), and declined during winter (2.5). According to the histological observation on ovaries, matured oocytes were also found in two seasons in a year; from April to June and from October to December. From those results, it is concluded that aramegarei of Wakasa Bay has semi-annual reproductive cycle with two spawning seasons in a year; spring and autumn. Moreover, it takes only half a year to spawn at the first time, especially for the fish born in spring. This small flounder, lives in coastal areas and is easily caught, with unique characteristics of maturation, can be a good model for reproductive physiology and ecology of fishes.

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Optimal conditions for sorus formation of Laminaria japonica were investigated by culturing discs of the sporophyte in bottles. All discs formed sori in the seven combinational conditions of temperature (5-15°C), irradiance (33.2-116 μE•m^-2•s^-1) and photoperiods (16:8, 12:12 and 8:16h LD) in nutrientrich medium. Sorus formation occurred earlier at 15°C than at 5 and 10°C and were largest in the area at 15°C. Sori grew larger under high irradiance (116 μE•m^-2•s^-1) than under low irradiances (66.4 and 33.2 μE•m^-2•s^-1), but the initiation of sorus formation was not influenced by irradiance. Sorus formation was earlier in 8:16h LD than in 12:12 and 16:8h LD. Rapid formation of large sori occurred at high temperatures even in a long photoperiod. Sorus formation in discs in nutrient-poor medium was slower than that in discs in nutrient-rich medium, in which all discs formed large sori. Most discs in nutrient-poor medium formed very small sori. These results indicate that water temperature and nutrient conditions strongly affect both to the induction and expansion of sorus formation.

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In the theory of the fish abundance estimation by quantitative echo sounders, we assume that object fish are at far range compared with the pulse length or the beam spreading. This assumption, however, deteriorates when the target fish are at near range. The time delay error which is caused by the finite pulse width, becomes serious, as Fernandes and Simmonds revealed, especially when we calibrate the quantitative echo sounder by the echo integrator outputs. This paper reviews our theory of fish abundance measurement focusing on the near range error to show necessity to incorporate a time delay in the range compensation function of the sounder. Further, we enumerate several near range errors and discuss them to give practical insight or countermeasures.

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Age and growth of the Japanese whiting Sillago japonica were examined from 908 fish specimens collected from October 1993 to January 1995 in Tateyama Bay, and growth curves were estimated by using a new method. Monthly changes in percentage of the otolith with opaque and translucent zones in the outer margin indicated that growth ring was formed once a year. Marginal increments of otolith formed annual rings from March and April. Ages of the fish were estimated to be 2, 3 and 4 years for both sexes. Using otoliths of 532 fish, growth in total length was expressed by the combined equation of the relative growth in total length and the radius, and the growth of ring radius as
L_t=602.5 (1-e^{-0.125 (t-0.02)}) for maie and
L_t=530.2 (1-e^{-0.149 (t-0.04)}) for female,
where L_t is total length in mm and t time in year. Growth in female and male were similar. The growth equations of the new and back-calculation methods were compared, and the difference of the parameter estimates, discussed.

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The maximal activities of 15 enzymes were compared in the striated and smooth adductor muscle, mantle muscle, foot, digestive gland, testis, and ovary of three species of scallops Chlamys nobilis, Pecten albicans, and Patinopecten yessoensis. The patterns of glycolytic enzyme activities in these three species of scallop were similar. However, the maximal activities of phosphofructokinase and malate dehydrogenase in the striated adductor muscle and octopine dehydrogenase in the striated and smooth adductor muscle differ significantly between species. All enzymes except for hexokinase were detected at the highest activity in the adductor muscle. In the striated muscle octopine dehydrogenase activity was highest among pyruvate reductases, followed by other opine dehydrogenases, D-lactate dehydrogenase. and L-lactate dehydrogenase. In these scallops phosphoenolpyruvate carboxykinase activity was very low compared with pyruvate kinase. Gonads and digestive gland showed fairly high activities of malate dehvdrosenase. asoartate aminotransferase. and alanine aminotransferase.

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Antibacterial substance for mutans streptococci was obtained from dried Gloiopeltis furcata by chromatographic separation. The substance was determined to be a mixture of free fatty acids (FFAs), from the results of instrumental analyses. The FFAs obtained showed moderate antibacterial activity against mutans streptococci, with minimal inhibitory concentration values between 25 and 50μg/ml. These FFAs also inhibited insoluble glucan production catalyzed by glucosyltransferase of Streptococcus sobrinus. Experiments carried out by using commercially available fatty acids indicated that unsaturated fatty acids showed more potent inhibition against insoluble glucan production than saturated fatty acids.

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Polypeptide chain elongation factor 1α (EF1α) was cloned from a liver cDNA library of medaka Orizias latipes. The analysis of the clone containing 1.6kbp DNA revealed that the entire open reading frame of EFla was 1383 bp long. Deduced amino acid sequence of medaka EFlα showed high similarity (more than 87% identity) with those of other vertebrates. Medaka EFlα had one amino acid deletion at the position of 447 amino acid of other EF1αs and unique 17 replacement against those of other vertebrates. Northern hybridization analysis revealed that this EF1α was expressed in all tissues tested.

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The cross-linking reaction was performed in the medium containing fish myofibrillar proteins, 0.5M (or 0.1M) NaCl, and 5mM CaCl₂ at pH 7.5 and 25°C with transglutaminases from carp muscle and the culture filtrate of a strain of Streptoverticillium mobaraense. Carp enzyme (CTGase) preferentially polymerized myosin heavy chains among individual myofibrillar components. Microbial enzyme (MTGase) also rapidly cross-linked myosin heavy chains at different sites from those with CTGase. Connectin (titin) was polymerized much faster than myosin heavy chain in soluble and aggregated states. The aggregated connectin was also cross-linked with CTGase at slow rate. Both enzymes could not cross-link actin molecules at all, though an amine (MDC) was incorporated to actin, suggesting the presence of active glutaminyl residue (s) as acyl donor.
Using fluorescent probes, lAEDANS-labeled actin and myosin, it was revealed that they were cross-linked with connectin by the action of MTGase and consequently their heteropolymers with huge molecular mass were produced together with connectin homopolymers.

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Effects of osmotic acclimation on apoptotic cell death of a fish cell line (Epithelioma Papulosum Cyprini, EPC) were investigated. The culture acclimated to moderate hypertonic medium (400mOsm/kg) showed less DNA fragmentation, the feature of apoptosis, with the exposure to severe hypertonic media (500 and 600mOsm/kg), than the culture acclimated to isotonic medium (300mOsm/kg). In contrast, the culture acclimated to moderate hypotonic medium (200mOsm/kg) exhibited more remarkable DNA fragmentation when exposed to the hypertonic media. The suppression of apoptosis by hypertonic acclimation could be explained by the shift of the threshold of osmotic pressure to trigger apoptosis. Because DNA fragmentation with the exposure to hypotonic medium was not observed in all the cultures acclimated to 200, 300, or 400mOsm/kg medium, EPC has an intrinsic viability against hypotonic environment.

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Red sea bream Pagrus major having a mean body weight of 18.5g were reared on diets containing 0, 10, 20, and 30% of rapeseed protein concentrate (RFC) for 52 days. Glucosinolates, sinapine, and phytic acid contents of RFC were respectively 0.58μmol/g, 0.2%, and 4.4%. Final mean body weights of fish fed the 20 and 30% RFC diets were lower than fish fed the 0 and 10% RFC diets. No significant differences among the dietary treatments were found in daily feed intake, feed efficiency, protein efficiency ratio, hematology, and relative weight of the hepatopancreas, stomach and intestine to body weight. Crude fat content of the whole body fell, but that of the hepatopancreas increased with an increase in diet RFC levels. Hematological character and plasma total protein, albumin, cholesterol, Mg and Zn concentrations did not show any differences among the dietary treatments. However, plasma P concentrations of fish fed the 0 and 10% RFC diets were higher than fish fed the 30% RFC diet. Moreover, apparent protein and sugar digestibilities fell slightly with an increase in dietary RFC contents. These results suggest that a practically substituitve limit with RFC for dietary brown fish meal is about 10% in red sea bream.

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The β-N-acetylglucosaminidase (β-GlcNAcase)-and chitinase-producing abilities of 283 strains in Aeromonas species from intestinal tracts of common carp Cyprinus carpio, crucian carp Carassius auratus, and gray mullet Mugil cephalus, and from their environment were determined using three fluorogenic 4-methylumbelliferone glycosides of N-acetylglucosamine oligosaccharides. As many as 91 to 100% of strains in each Aeromonas species produced at least one of three enzymes, such as β-GlcNA-case, exo-chitinase and endo-chitinase, and 58 to 80% of strains could produce all three enzymes. Enzyme activities varied remarkably with species and strains, along with bacterial sources, and 20 to 55% of A. hydrophila (except for β-GlcNAcase), A. jandaei (except for β-GlcNAcase) and A. sobria showed high activities (>0.1U/mg) of β-GlcNAcase and chitinase. Moreover, there was a significant strain-to-strain variation in composition of chitinoclastic enzymes even within genospecies. These results suggest that the predominant aeromonads in the intestine of freshwater fish play an important role in the digestion of injested chitin-bearing organisms.

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