From February 1990 to July 1992, the reproduction of the blue shark, Prionace glauca, in the south-western equatorial Atlantic Ocean was studied. During this period, 88 females and 82 males were examined. Females were found in 4 different sexual stages: preovulatory (22), pregnant (47), postovulatory (non-pregnant) (7), and subadult (12). Their fork length ranged from 162 to 225cm. Half of the females were in early pregnancy. Embryos in completely different stages of development were found in 4 of them. Oviducal glands of 44 females were examined and in 38 spermatozoa were found. These results indicate that ovulation and fertilization took place from December to July. Most of the males were adult and only 14 specimens seemed to be sexually immature. Many adult males were lacking sperm packs and had a very low volume of seminal fluid, suggesting that they were probably sexually resting. Their fork length ranged from 156 to 228cm.

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Using marine Chlamydomonas as food, the food requirement of bisexual brine shrimp Artemia franciscana was estimated in terms of nitrogen in order to assist production. The ingested food was theoretically fractionated to the maintenance, somatic growth and reproduction of nauplius and cyst. While feeding marine chlamydomonad (5 pg N/cell) to the shrimp (Lmm), the daily maintenance ration was almost proportional to the cube of body length (2.952) and was 2844 cells/shrimp/day for shrimp of 1mm length at 28°C. On the basis of ingested food, the somatic food conversion efficiency was 67%. The efficiency of nauplius production was 23% and that of cyst production was 44%, based on the food taken by a pair of shrimps. Including the reproductive products as growth, the gross conversion efficiency was 16% in the groups from which the maintenance ration and somatic conversion factor were obtained, and 24% in the groups from which the reproductive conversion factors were obtained. The reproductive growth per total growth increased with the body length and the feeding rate, and was zero below 5.7mm in length and 1.0 times the daily maintenance ration.

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Using marine Chlamydomonas as food (5 pg N/cell), the apparent assimilation efficiency in the bisexual brine shrimp Artemia franciscana was estimated in terms of nitrogen in order to assist production. The apparent assimilation efficiency was defined as the ratio of food required for a given growth to the ingested food. Using the previously reported data on the growth, daily ration, maintenance ration and food conversion factors (in seawater at ca. 28°C), the assimilation efficiency was estimated. The regression of efficiency vs. body size and daily ration was presented in the range where the efficiency is less than 100%. This regression showed that the amount of apparently assimilated food decreased with increase in feeding rate above a certain level and gave the reason for decrease in growth speed at higher daily ration. The error in the estimation of efficiency was also discussed.

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The clotting time using Russell's viper venum (RVV) was examined in common carp plasma. The best condition for the assay of RVV time was obtained in a 1:30, 000 dilution of RVV with Platelin suspension and M/20 CaCl₂ solution. Common carp plasma was also subjected to chromogenic substrate assay for human factor X. The dilution curves of RVV time (RVVT) and chromogenic substrate assay were made from serial saline dilutions of pooled normal plasma. Reductions in coagulation factors had no marked effects on prolongation of RVV time until reaching a dilution less than approximately 30%. The activity converted from RVVT showed a linear relationship between the activity converted from chromogenic substrate assay within the range from 100 to 40%.

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The white shark was thought to be rare in Japanese waters except Okinawa, but the author doubted its rarity because of its coastal and temperate habitat and eurythermal nature. Therefore, records of large sharks were collected since 1992 and closely examined. Nineteen of sharks were the white shark Carcharodon carcharias, and such a high incidence in catches or sightings in only 18 months is surprising, because previous published records indicate for fewer numbers. Since many of the larger sharks are not landed because of their low commercial value, and since smaller specimens were not included in this survey, the white shark is not a rare species in Japan.
The white shark is known to exist in waters of 7 to 27°C (mainly 15 to 22°C), and its eurythermal nature suggests that the species can remain all year round in the southern and middle parts of Japan. However, the white shark seems to be a seasonal visitor to the waters of northern Honshu and Hokkaido.

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Anemia caused by hemolysis occurred in coho salmon Oncorhynchus kisutch infected with the erythrocytic inclusion body syndrome (EIBS) virus. Bilirubin levels were significantly higher in the plasma of diseased fish than in healthy fish. Hyperbilirubinemia occurred in fish infected with EIBS virus. Erythrocytic superoxide dismutase activities were induced in the diseased fish. The liver bilirubin level of diseased fish was much higher than that of control fish, while the total bile acid level in the plasma of diseased fish was much higher than in the control. The plasma astaxanthin level in the diseased fish was lower than that in the control, whereas plasma vitamin A levels of both were similar. These results suggest that excretion of bile acid decreased in the diseased fish. The accumulation of bilirubin in the liver and the disfunctional bile acid excretion indicate that secretory disorder of bilirubin occurred in the diseased fish and was one of the causes of hyperbilirubinemia observed in coho salmon infected with EIBS virus.

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Two types of clones of the ayu Plecoglossus altivelis heterozygous and homozygous clones, were produced by crossing second generation gynogenetic diploids with sex reversed clones of a different or the same line, respectively. Samples of these fish, together with normal control diploids, were used in this study to monitor the expected reduction of the genetic variance in the clonal lines. The morphological traits measured (body weight, fork lengtht and gonad weight) showed a significant reduction of the coefficient of variation (C. V.) of 44.8% on average (heterozygous clones 56.17%, homozygous clones 33.4%). Furthermore, from all the physiological traits evaluated, hematocrit, plasma glucose, and mean corpuscular hemoglobin concentration (MCHC), also showed a significant variation reduction of 42.33% (average) for the heterozygous clones and 13.4% (average) for the homozygous clones. An estimation of the heritability of both kind of traits is proposed, based on a substantial elimination of the genetic variation in the clonal lines.

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Rearing experiments were carried out to examine the effects of temperature on the growth of Japanese flounder Paralichthys olivaceus at 10, 15, 20, 25, and 30°C with fish of about 4, 16, 88, and 176g initial body weight. Fish were fed to satiation twice a day with a commercial pelleted diet for 20 days.
In all body weight groups, the daily growth rates increased with temperature up to 20 or 25°C, though there was little difference in the rates between these temperatures. However, the rates decreased at 30°C. The daily feeding rates also increased with temperature up to 25°C, while the feed conversion efficiency decreased above 20°C. Therefore, the optimum temperature for the growth of Japanese flounder of the sizes tested is probably between 20 and 25°C.
The daily growth rate at 30°C decreased more in larger flounder (88 and 176g) than in smaller ones (4 and 16g), and the higher catabolic rate at 30°C for larger flounder appeared in the relationship between feeding rate and growth rate. Therefore, the high energy expenditure for catabolism appears to reduce the energy available for growth of larger flounder at 30°C.

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We have developed an in situ spinal cord preparation of a teleost for studying neural mechanisms underlying motor rhythms during swimming. Adult carp were anesthetized with pentobarbital injection and immobilized with curare injection. Motor rhythms were monitored by recordings from ventral roots with a suction electrode. Fictive swimming was elicited by either midbrain micro-stimulation or tactile stimulation of the skin. Both stimulation methods elicited motor rhythms corresponding to swimming of intermediate speeds. Moderate touch stimuli such as stroking of the mouth and the caudal fin seemed to be appropriate stimuli for inducing a motor rhythm equivalent to swimming. Stronger stimuli such as pinching the caudal fin only evoked a few, brief bursts of activity at irregular intervals. The noxious stimuli are assumed to be mediated by pathways other than those for stimuli of moderate strength. The stimulation methods employed in the present study involve some problems, in particular, artefacts from stimulation currents often mixed with electrical records, and careful manipulation was needed to maintain a desirable level of anesthesia.

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In this study, we investigated the ovulation cycles, time course of a decline of fertilization rate due to over-ripening, and effect of semen quality on the fertilization rate, in order to establish an efficient technique of artificial fertilization in barfin flounder Verasper moseri. The ovulation cycle of this species is 3 to 4 days at 6°C. The fertilization rate of the eggs pressed out just after ovulation attained about 90%, gradually decreasing with time after ovulation, and fell to 45% on average 2 days after ovulation. The difference of the spermatocrit values had little influence on the fertilization rate. These results indicate that the fertilization rate depends primarily on the time after ovulation. It is important for successful fertilization to estimate the ovulation date by checking ovulation during the early spawning season, and to use fresh eggs soon after ovulation.

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The postvitellogenic oocytes of daily spawning marine teleosts, tobinumeri-dragonet Repomucenus beniteguri and kisu Sillago japonica, undergo germinal vesicle breakdown (GVBD) in vitro in the presence of maturation-inducing steroids (MIS). The responsiveness of the oocytes to MIS appears a few hours before ovulation, and the oocytes collected earlier than this time are insensitive to MIS. In the present study, the effects of gonadotropin (GTH) on the development of sensitivity to MIS were examined in vitro in the oocytes of these two species. The oocytes which were collected 13-16 h before ovulation and insensitive to MIS were first incubated in medium containing GTH for a short period (10 to 300min in dragonet and 1.5 h in kisu) and subsequently incubated for a longer period (up to 24 h in dragonet and 18 h in kisu) in medium with or without 17α, 20β-dihydroxy-4-pregnen-3-one (17, 20-P). Following short-term treatment with GTH, the oocytes became sensitive to 17, 20-P and underwent GVBD. A short-term GTH treatment only did not induce GVBD in these oocytes. The present results indicate that GTH develops sensitivity to MIS in oocytes in dragonet and kisu.

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One day old larvae of the Japanese croaker Nibea japonica were exposed to low levels of ammonia, at concentrations of 0.0027, and 0.027mg/ml NH₃-N (un-ionized ammonia) for 72 h. High mortalities were observed in the groups exposed to 0.0027 and 0.027mg/l NH₃-N. Because these ammonia levels are frequently found in the nursery ponds of various species, the acceptable ammonia concentrations for larval culture must be reevaluated.
In the second experiment, 3-day-old N. japonica larvae were exposed to a high level of ammonia (0.26mg/l NH₃-N). Pathological changes were observed in the skin by light and electron microscopy. The changes included reduction in the number of mucous cells, cytoplasmic vacuolation, rough apical surface of the epithelial cells and degeneration of the mitochondria of the chloride cells.

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Mass mortalities of hatchery-reared juvenile Japanese flounder Paralichthys olivaceus were investigated. The disease initiated in fish of 17-18mm in total length and heavy mortalities occurred when the fish reached about 25mm, followed by total losses in 2 weeks. The disease was characterized by vacuolation in the retinal and brain tissues. Round-shaped, unenveloped virus particles, about 27 nm in diameter, were observed in the cytoplasm of retinal and brain cells. The virus was identified as a nodavirus based on the results of FAT using an anti-SJNNV (striped jack nervous necrosis virus) rabbit serum and PCR-based detection of a portion of SJNNV RNA 2 gene. Transmission experiments revealed that the virus is the causative agent of this disease. In addition to the nodavirus, another virus (YAV-like birnavirus) was isolated in EPC and FHM cell lines from diseased fish. However, the latter virus is not thought to play an important role in this infection.

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Rupture tests and stress relaxation tests were carried out to distinguish between raw meat of a cuttlefish, “kou ika” Sepia esculenta, and that of four squids, “yari ika” Loligo bleekeri, “Argentine matsu ika” Illex argentinus, “surume ika” Todarodes pacificus, and “New Zealand surume ika” Nototodaus sloani sloani, respectively. The rupture force and the rupture work were positively proportional strength and rupture power could be estimated from the parameters obtained through the rupture tests. Linear relationships with high correlation coefficients were obtained between the rupture power as well as relaxation time and the water content or crude protein content of samples. Each “ika” raw meat of the different species could thus be distinguished from its rheological properties.

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A purple-colored bacterium was isolated from the body of a marine sponge Adocia sp. The culture of this bacterial isolate produced a substance which inhibited the growth of Staphylococcus aureus and Bacillus subtilis. The substance was purified and consequently identified by various spectrometric methods as O-aminophenol. Moreover, the extract of the host sponge did not contain any antimicrobial activity against these two Gram-positive bacteria.

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The effects of environmental factors such as light illumination, black and white substrates, salinity, temperature and hydrostatic pressure on larval settlement of the reared barnacle Balanus amphitrite were examined. Settlement was found to be sensitive to the light intensity and color of substrates, and was observed over a wide range of salinity, temperature and hydrostatic pressure.

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The lined moon shell Natica lineata was seasonally collected from two places in Taiwan, Kaohsiung City, and Pintgung Prefecture, and assayed for anatomical distribution of tetrodotoxin (TTX) and aerobic hetrotrophic bacteria. Kaohsiung specimens showed a higher toxicity than Pingtung ones. At either place, the gastropod exhibited the highest toxicity in February. The aerobic bacteria counts exhibited an outstanding seasonal variation: 10⁸ CFU (colony forming unit)/g in August 1990, reducing to 10⁵ CFU/g in February 1991, and then increasing to 10⁶ CFU/g in May 1991. Predominant genera were Vibrio, Aeromonas, Flavobacterium, and Pseudomonas. Vibrio comprised more than 46% of the genera, with V. alginolyticus as the major one. However, there was no relationship between the total viable counts and the toxicity of the shellfish. HPLC, UV, and GC-MS analyses demonstrated that some bacteria when isolated, such as V. alginolyticus and Aeromonas spp., produced TTX and/or related substances.

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The effect of extrusion on the nutritional value of corn meal for grass carp Ctenopharyngodon idella and hybrid tilapia Oreochromis niloticus×O. aureus fingerlings was studied. Raw and extruded corn meal were mixed in five proportions at a 50% level in the diet, with a gelatinized ratio (GR) ranging from 29 to 100%.
The apparent starch digestibilities improved gradually by increasing the GR level. The energy digestibility was slightly improved in grass carp, while it was almost constant in tilapia. The percent gain, feed efficiency and protein efficiency ratio improved smoothly by increasing the GR level. However, the feed efficiency was still high (114% for grass carp and 119% for tilapia) even in the fish fed on a diet with raw corn meal. In tilapia, the daily feed consumption was not related to the GR. In the whole body composition, an increase of lipid content was observed with an increase of GR.
A gradual increase in gelatinization thus improves gradually the nutritive value of corn meal for grass carp and tilapia. However, the effect is not so strong. Both species are good at utilizing corn meal, even in its raw form and at a high concentration, particularly tilapia.

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This study investigated the nutritive value of gelatinized corn meal to common carp, including the effect of gelatinization on intestinal evacuation and starch digestion. Fish were fed diets containing raw and extruded corn meal in three proportions at a 40% dietary level, with dietary gelatinized ratios (GR) of 28, 72, and 100%.
In the first experiment (growth trial) with fingerlings, the percent gain was similar in all groups, but feed efficiency and protein efficiency ratio improved with increasing level of GR. The daily feed consumption decreased with increase of GR. The starch apparent digestibility improved by increasing the GR level. The energy digestibility also slightly improved with increase of GR.
In the second experiment (evacuation trial) with juveniles, the food evacuation time from the anterior section of the intestine was very similar in all diets, suggesting no difference in food passage time in the digestive tract. The apparent starch digestibility in the different sections of the intestine increased gradually with time after feeding in all diets. However, starch digestion was much faster for the diets with higher GR.
It can be concluded that an increase of gelatinization ratio improves the nutritive value of corn meal for common carp and this might be due to the acceleration of starch digestion in the intestine.

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The changes in contents of ATP and its related compounds were examined in the mantle, arm, and fin muscles of spear squid Doryteuthis bleekeri during storage at 5°C. The efficacy of the values of K, K', A. E. C., Hx ratio, Xt ratio, and Hx/AMP ratio were evaluated as freshness indices. The level of ATP at time 0 and the total content of ATP and its related compounds in the mantle muscle were higher than those in the other 2 muscles. In all muscles, ATP decreased rapidly 1 day after the beginning of storage and Hx increased markely during storage. The degradation of AMP was considered to proceed through 2 pathways, IMP and AdR pathways, in all 3 muscles. In the mantle and fin muscles, K and K' values increased markedly within 4 days of storage and may be used as freshness indicators in earlier periods of storage. The Hx, Xt, and Hx/AMP ratios increased continuously during storage; the changes in the Xt and Hx/AMP ratios were larger than those in K or K' values. It was suggested that the ratios of Hx, Xt, and Hx/AMP are more useful as freshness indices for spear squid than the K value.

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The qualitative requirements and deficiency signs of water-soluble vitamins were studied in tiger puffers Takifugu rubripes having mean body weight of 2.9g.
The qualitative requirements of tiger puffer for water-soluble vitamins indicate that the requirement of this species for vitamin B₆ is lower than that of other fish species such as red sea bream, yellowtail, and Japanese parrot fish, while that for vitamins related to lipid metabolism, such as choline, nicotinic acid, pantothenic acid, biotin and inositol, is comparatively high.

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Two genetically distinct a components were isolated from each of the major and minor collagens, Type SQ-I and SQ-II collagens, from the mantle muscle of squid by phosphocellulose column chromatography, called α1 (SQ-I) and α2 (SQ-I), α1 (SQ-II) and α2 (SQ-II), respectively. The α1 (SQ-I) and α1 (SQ-II) components were shown to be genetically distinct from each other by peptide mapping and amino acid analysis. On the other hand, the α2 (SQ-I) and α2 (SQ-II) components, which migrated at almost the same position on SDS-PAGE, were similar in peptide map and amino acid composition. However, slight differences were observed in both features, suggesting genetic differences. From the results, Type SQ-I and SQ-II collagens were demonstrated to be heterotrimers [α1 (SQ-l)]₂α2 (SQ-I) and [α1 (SQ-II)]₂α2 (SQ-11), respectively.

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The ultraviolet (UV) denaturation of flying fish myosin, subfragment-I (S-1), and rod was examined by means of solubility test, CD measurement, 8-anilino-1-naphthalene sulfonate (ANS) intensity, and tryptophan fluorescence intensity measurements. Solubilities decreased in order of myosin>rod>S-1 during UV irradiation. CD curves also showed that the α-helical content of myosin and its fragments decreased rapidly with increase of UV intensity and the duration of irradiation. The fluorescence intensities of UV-irradiated myosin-ANS and S-1-ANS decreased after increasing for 10min, but the rod-ANS decreased without increasing. UV irradiation caused a marked decrease in the tryptophan fluorescence intensity of myosin and rod. The SDS-PAGE patterns revealed that myosin heavy chain polymers were formed during UV irradition.

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Brown discoloration of freeze-dried short-finned squid meat imparted by the Maillard reaction during storage at 25°C was examined as a function of water activity (A_W). The reaction took place fairly fast in intermediate A_w's between 0.4 and 0.7. Similarly, the losses of reducing sugars, glucose, free amino groups, and available lysine during storage were maximum at intermediate A_w's. On the other hand, myosin heavy chain (MHC) content in freeze-dried squid meat decreased as the polymerized subunits of MHC increased during storage. From the developing trends of the Maillard reaction including the increase of discoloration and the decreases of reducing sugars and free amino groups in freeze-dried squid meat, it is suggested that the polymerization of MHC during storage is mostly attributed to the Maillard browning reaction. This was confirmed by experiments using squid meat which had been thoroughly washed with water.

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In order to investigate the metabolic response to dietary glucose, fructose, and galactose in carp Cyprinus carpio, tolerance tests of these monosaccharides and feeding trials were conducted. After oral administration of 50mg of glucose, fructose or galactose per 100g body weight, serum glucose, fructose, and galactose levels increased to the maximum until 1.5 h. Although these sugar levels decreased thereafter, the decreases of serum glucose and fructose levels were faster than the decrease of serum galactose levels. In the feeding experiment, carp were fed on a high-protein diet and four diets containing 30% of starch, glucose, fructose, and galactose for 30 days. The fish fed galactose showed a remarkable reduction of growth rate, several body component levels, and hepatopancreatic enzyme activities. Dietary supplementation with starch, glucose or fructose depressed the activities of gluconeogenic and amino acid degrading enzymes and raised the activity of phosphofructokinase. The activities of lipogenic enzymes and the levels of serum lipids were raised by dietary starch and glucose but not by dietary fructose. These results suggest that both glucose and fructose in the diet depress gluconeogenesis and amino acid degradation and accelerate glycolysis, but that fructose, unlike glucose, does not promote lipogenesis in the hepatopancreas of carp.

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