To establish a seed production technique for marble goby Oxyeleotris marmoratus the eggs and larvae were observed under artificial rearing conditions. Newly ovulated eggs from a female of 255g in body weight were measured 0.94 and 0.62mm in the long and short axes, and weighed 1, 669.6 eggs/g. After fertilization, the egg had a bundle of adhesive filaments at the basal end of the egg membrane and was elongated after 1h, when it measured 2.3 and 0.63mm in its long and short axes, respectively. The eggs hatched during 41-150h after fertilization (AF) at 27.2-27.5°C. Early and late hatching resulted in high mortality. The optimum hatching stage was considered just before and after the embryonic eyes had become slightly pigmented. All embryonic heads were located at the basal part of the egg and this was taken as normal egg development for O. marmoratus.
In spite of their well-developed eyes and mouths, and the fact that they exhibited the active S-posture, the larvae did not feed on artificial powdered feed or Brachionus spp. for 4-6 days (d) AF, and the mortality before the feeding of Brachionus spp. was much higher than that of the later stages. They shifted their habitat from pelagic to benthic from 30 d AF. About 1, 600 seeds (mean total length, 28.5mm) were produced from 16, 000 hatched larvae (mean total length, 3.54mm) at 70 d AF.

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The effects of osmotic pressure and diluent composition on the initiation and duration of spermatozoan motility in the pejerrey Odontesthes bonariensis, a fresh water atherinid fish, were investigated. Spermatozoa were immotile in the seminal fluid (mean osmotic pressure 331 mOsm/kg), but became motile by dilution with fresh water (4 mOsm/kg), urine (64 mOsm/kg), non-electrolyte solutions (sucrose, mannitol, glycerol) up to 388 mOsm/kg, electrolyte solutions (sea-water, KCl, NaCl) up to 551 mOsm/kg, and KCl solution at 715 mOsm/kg. Increases in the osmotic pressure of the medium caused progressive reduction in the percentage of motile spermatozoa until complete immotility at 878 mOsm/kg. Thus, osmotic pressure appears to be the major factor regulating the motility of pejerrey spermatozoa, but the presence of cations, especially potassium, is equally capable of inducing motility. The presence of potassium also greatly extended the duration of motility. With the exception of NaCl solutions at 388 and 551 mOsm/kg, all hyperosmotic diluents irreversibly damaged the spermatozoa during a 10-min exposure. These results are discussed in relation to present knowledge on the initiation of motility of fish spermatozoa and the development of fertilization media and sperm preservation techniques for the artifical propagation of pejerrey.

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This paper proposes a method for estimating a relative index of stock abundance using age compositions in the catch and estimates of fishing and natural mortality coefficients. The relative indices of the stock size and catch are defined by the ratio of these to the total catch in the first year of estimation. Using the indices a backward equation similar to that of Virtual Population Analysis (VPA) was obtained. Values of parameters are estimated by the least squares approach with estimates of mortality coefficients. Results of simple simulations using artificial data showed that the trends of the estimated relative indices of stock size were close to those of the true values, except under scenarios of existing bias in mortality estimates. Application of the method to data for the red sea bream, Pagrus major, in the eastern Seto Inland Sea indicated that the trends from the method and VPA were similar to each other. The problems in application were discussed.

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This study reports on the locomotor activity rhythms of Paramyxine atami exposed to expanded and contracted photoperiodic regimes (T in hours) divided into light and dark periods of equal duration. Nocturnal activity was entrained by the range of 23.5h_??_T_??_25.2h on average. Above and under this range, the activity signals entered the light period with pronounced individual variability: complete or partial dispersion in the light period and occurrence of active phases in both light and dark periods with relatively constant period length of activity (PL). In the latter case, PL averaged 22.9h for contracted regimes, and 24.2h for expanded regimes, while it averaged 23.9h under constant T=24. The circadian period (τ) of fish which were shifted to continuous darkness (DD) after engagement in contracted regimes and expanded regimes averaged 23h and 25h, respectively. The similarity between τ and PL values suggests that the period lengths of activity rhythms are strictly regulated to around 24h by the endogenous time control system, while the relative coordination of the activity rhythms to external light cues is still retained within a small variation of T from 24h.

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An index is proposed to evaluate stock overfishing using catch and effort data. The overfishing index is defined as the slope of the parabola curve between stock size and surplus yield at a given stock size. The value of the index is calculated from estimates of parameters of dynamic production models and observed catch per unit effort. The sign of the index indicates the stock state: overfishing if positive, MSY level if zero, and non-overfishing if negative. The index is useful in displaying changes in the stock state over time. Monte Carlo simulation experiments are carried out to suggest that the sign of the index has robustness against stochastic errors in the catch data as well as difference in the models. Limitations of the present method are discussed after applying it to the actual data.

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Using an allozyme marker (i.e. MPI^*), we traced the mixing rate of the landlocked ayu-juveniles from Lake Biwa released in the Yasuda River and the Ioki River, inhabited by a native amphidromous form. We also estimated the population density based on under-water observations. The percentage of the landlocked form was remarkably high in the upper stream and very low in the lower stream in June. The percentage of the landlocked form decreased remarkably in the upper stream in both rivers in August. The percentage of the landlocked form decreased to almost zero in December. These seasonal changes in the mixing rate of the landlocked form suggested a difference in the migration pattern of the landlocked form and the amphidromous form in the river. The number of the amphidromous form coming up to the river from the sea was estimated using the landlocked form's percentage and the population density observed at each location during the early fishing season.

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Female red-spotted masu salmon, Oncorhynchus masou ishikawai, collected in a small stream in Honshu Island, Japan, were examined for ovulated eggs, which were not oviposited during the preceding spawning season. Nearly half of the specimens collected in 1984 had some retained eggs in the abdominal cavity. In addition, some females had both well-developed gonads and ovulated eggs, indicating that they spawn at least twice during their lifetime (iteroparity). The smaller the female body size, the more the retention of ovulated eggs and their proportion of the overall egg total. Such eggs are probably resorbed for energy during the non-spawning season, hence improving their growth and/or survivorship and, consequently, future reproductive success.

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The distribution and seasonal density of the finless porpoise were examined in the coastal waters of western Kyushu, Japan in 1987-1992 by ship sighting surveys and interview surveys with fishermen and ferry crews. Interview surveys showed that the porpoise may occur rarely in Sumo Nada and the waters of northern Nagasaki Prefecture and that it was found frequently in Ariake Sound, Tachibana Bay, and Omura Bay. In ship surveys by the line transect method, mean densities in the middle and mouth of Ariake Sound were estimated as 1.31-1.60 and 0.341 individuals/km, ² respectively. The porpoise density in the middle of Ariake Sound increased from September to April and showed a minimum in August. In the mouths of Ariake Sound and Tachibana Bay, the sightings became higher in summer. The porpoise distribution was considered to shift seasonally between the two seas. Water depth and distance from the coast seem to influence porpoise occurrence. Porpoises may favor depths of less than 50m and distances of less than 2-3 nautical miles. The season of high density in Ariake Sound coincided with the reported calving season but not with the increase in the mean school size. The mean school size was 1.70 (SE 0.05).

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Several cell lines producing monoclonal antibodies against carp fast muscle myosin were obtained by fusion of immunized BALB/c mouse spleen cells with syngenetic NS-1 myeloma cells and subsequent cloning by the limiting dilution method. Monoclonal antibodies, which were obtained when myosin was injected to mice as an antigen, recognized myosin subfragment-1 (S 1). Further assignments for antigenic sites in the S1 molecule revealed that antibodies from 35A11 and 41C2 cell lines were specific to 50 and 25 kDa fragments of S 1 tryptic digests, respectively. No cell line producing monoclonal antibody specific to the 20 kDa fragment of S 1 tryptic digests was established. On the other hand, cell lines for monoclonal antibodies against myosin rod were established only when the rod was administered to mice as an antigen. The 37G3 cell line produced the antibody specific to myosin rod and reacted with its light meromyosin part. However, all monoclonal antibodies thus raised failed to discriminate between two types of myosin from carp acclimated to 10 and 30°C, irrespective of myosin S 1 or rod.

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The distribution of neuropeptide Y (NPY)-like immunoreactivity in the abdominal ganglion of the common sea hare Aplysia kurodai, was studied by a streptavidin-biotin technique, with special regard to a possible relationship with the molluscan cardioexcitatory tetrapeptide, FMRFamide. NPY immunoreactive cells and fibers were found in a wide range of the abdominal ganglion and its derivative peripheral nerves, such as the pleuro-abdominal connectives, vaginal nerve, branchial nerve, siphon nerve, and genital-pericardial nerve. Examination of correlative sections, immunostained alternatively with anti-NPY and anti-FMRFamide antisera, indicated overlapping distribution of the immunoreactive structures in the abdominal ganglion. Cross-blocking experiments revealed that NPY-immunoreactivity was negated by preabsorption of the antiserum with homologous antigen, but not so by pretreatment with FMRFamide. The converse situation was obtained for FMRFamide-immunoreactivities. Accordingly, the NPY-like or FMRFamide-like immunoreactive structures of the abdominal ganglion of Aplysia were revealed by a single antibody, FMRFamide-antiserum or NPY-antiserum, respectively, and their apparent colocalization was demonstrated.

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DeLury's method was expanded to 14 maximum likelihood models with variable catchability coefficients (q_i) according to such environmental factors as water temperature, lunar cycle, and the intensity of ocean waves. The optimal model was selected by AIC, after the application of the models to catch-effort data from Japanese spiny lobster gilinet fishery. Confidence intervals of the estimators for each model were also discussed with a likelihood ratio test. AIC values greatly improved when variable catchability coefficients were assumed. Judging from the estimated parameter values, q_i is large in conditions such as when (1) water temperature is high, (2) the phase of the moon is around the new moon, and (3) ocean waves are intense. When the relationship between q_i and the water temperature was treated separately in two different functions for decreasing and increasing periods of water temperature, and when a five-day moving average of water temperature was introduced, the AIC values improved further. These variations in q_i were probably attributable to changes in the activity of lobsters according to the fluctuation of environmental factors.

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Laboratory cultures of the mussel (Mytilus edulis galloprovincialis) larvae have been attempted, in order to obtain large amounts of pediveliger larvae which are used for studies on mechanisms of larval settlement. Adult mussels were collected from either Mutsu Bay, Aomori or Aburatsubo Bay, Kanagawa, Japan, from which D-shaped larvae were obtained by artificial fertilization and successfully cultured to the pediveliger stage. In a typical case, 7-10 individuals/ml of D-shaped larvae were cultured in 1 l and 10 l scales at 19±1°C by feeding 1.0-1.5×10⁵ cells/ml of Isochrysis galbana. They reached the pediveliger stage 14-21 days from the start of culture. Shell heights at the time of appearance of pediveligers were 171.16±14.35-228.34±24.55 μm. Survival rates when larvae reached the pediveliger stage were 48.5-86.7%. Competent pediveliger larvae were allowed to attach and metamorphose on glass slides on which microbial film had formed. Metamorphosis was completed in 2-3 days, as confirmed by secretion of the adult shell. The rate of post-larval shell growth was approximately 22 μm/day. Thus, we were successful in developing a culture method for the mussel larvae.

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To elucidate the substance which causes fluorescence in black-lip pearl, the substance was extracted from black-lip pearls with 2_N-HCl. After being fractionated by talc column chromatography, the substance was converted to methyl ester. Using uroporphyrin I octamethyl ester as a standard, the esterified substance was compared in terms of visible absorption spectra, fluorescence emission spectra, and high performance liquid chromatographic behaviors. Considerable similarities in absorption peaks, fluorescence peak, and retention time resulted between the esterified substance and the standard. From these results the substance was proved to be uroporphyrin I. The experimental result of the existence of porphyrin facilitates percent pearl identification.

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In order to obtain basic knowledge for promoting seed production of the striped jack Caranx delicatissimus, chemical composition, nucleic acid contents, and alkaline phosphatase activity (ALP) were measured in the fish, from larvae through juveniles at 1-3 day intervals.
While rearing on rotifer, Artemia nauplii, and an artificial diet in that order, the total length of the fish increased satisfactorily from 2.8mm in the hatching larvae to 23mm in the juveniles on day 42. Moisture decreased slightly throughout the rearing period. Crude protein and ash increased steeply until day 17, the morphological sifting point from larvae to juvenile, but triglyceride and phospholipid temporarily fell in three periods of days 1-6, 14-16, and 24-28. DNA content and the RNA/DNA ratio respectively decreased and stepped up in periods of days 14-22 and days 34-42, except for steep increases by day 8. ALP increased on days 3-6 and then maintained high levels until day 14.
These indicate that growth in the early life stages of striped jack is supported by cyclic phases of hyperplasia and hypertrophy while conducting quantitative and qualitative changes in body composition and enzymes as well as morphological development.

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The activities of α-amylase, α-glucosidase, hexokinase (HK), phosphoglucomutase (PGM), and phosphorylase were determined monthly in fresh ascidian muscle and changes of glycolytic compounds during storage at 2°C were investigated bimonthly.
Most of the enzymatic activities were lowest in summer and highest in winter. α-Glucosidase, HK, and PGM showed conspicuous changes seasonally while α-amylase and phosphorylase showed slight ones. Glycogen in fresh ascidian muscle was highest in summer and lowest in winter wherease glucose showed a seasonal change in the opposite manner. Glucose 6-phosphate, fructose 6-phosphate, and lactic acid in fresh muscle fluctuated throughout the year and their seasonal variations were obscure. During storage, glycogen was degraded and other metabolites in question accumulated. The degradation of glycogen and the accumulations of glucose and lactic acid were noticeably faster in winter than in summer. These findings suggest that ascidian adapts enzymatically to environmental changes, especially to attain certain catalytic efficiency in winter and, as a result, that high enzymatic activities in winter can enhance rapid postmortem changes in the ascidian muscle.

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A total of 26 species of seaweeds (1 green, 21 brown, and 4 red algae) and 6 polysaccharides were screened for their antihypertensive and antihyperlipidemic activities using rats in order to evaluate their potential application for the prevention of cardiovascular diseases. Although diets containing some pulverized seaweeds moderately elevated total cholesterol (TC), free cholesterol (FC), and low density lipoprotein (LDL), marked antihypertensive and antihypercholesterolemic activities were found in almost all seaweeds, some of which are commonly used as food. In addition, serum levels of high density lipoprotein (HDL) were enhanced 46.0% by seaweed powder diets. Six polysaccharides derived from active seaweed species were investigated, and appreciable suppression of hypertension and hypercholesterolemia was observed for all samples. They also markedly enhanced the serum level of HDL.

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To elucidate the mechanical process in meat during high pressure treatment, we attempted to describe thermodynamically the mechanism of meat denaturation on the basis of volume changes, enthalpy changes, and rheological properties.
Carp meat was pressurized up to 196 MPa for 13h at 0-5°C. The volume of meat was irreversibly changed by pressurizing for more than 4min. After 2h of pressurization, the ratio of volume change (V₀-V)/V₀, where V₀ and V were the volumes of unpressurized and pressurized samples, respectively, attained a constant value of ca. 0.11. The results of dynamic viscoelastic measurement on the meat paste showed that the pressurized meat gave a fine network structure of meat gel by heating. A comparison of the results of differential scanning calorimetry with volume changes by pressurizing suggested that there was a similar denaturation mechanism in both heating and pressurizing.

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This investigation focussed on the changes effected at the cell membrane level in rainbow trout under various dietary fatty acid regimes. Fish were grouped as essential fatty acid (EFA) deficient (fed on palmitic acid) and adequate (fed either on linoleic, linolenic acid or on n-3 highly unsaturated fatty acids). After feeding for three months, blood samples were collected and the osmotic fragility of the red cells was assayed by measuring hemolysis at different gradient saline solutions. Membrane lipids were extracted and the fatty acid composition of the polar lipids was determined to complement the observations on osmotic fragility.
The red cells of fish fed on an EFA-deficient diet were more fragile when compared to those receiving different EFAs from the diets. The fatty acid profiles clearly reflected the dietary provisions. It appears that the strength of the erythrocyte membrane is influenced by the unsaturation index of the polar lipid component. The fact that fatty acids in the diet are particularly important for the structural integrity of cell membranes has been authenticated by examining the osmotic fragility of erythrocytes in rainbow trout.

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Production conditions and some properties of the extracellular protease produced by Cytophaga columnaris isolated from a diseased Japanese eel Anguilla japonica were examined. The enzyme production was stimulated by the addition of pepton (Kyokuto) and sodium acetate. Divalent metal ions such as Mg²⁺, Ca²⁺, and Mn²⁺ were also required, and the addition of yeast extract at the restricted concentration increased the enzyme production. Optimum pH range of incubation for the enzyme production was between 6.8 and 7.0, and the optimum temperature of incubation was around 25°C. The enzyme production occurred with the growth of the organism, and the enzyme was accumulated during the stationary phase of growth in a liquid medium under aerobic conditions. The proteolytic activity in the culture supernatant was inactivated at 60°C for 60min, and the activity was reduced to 78% at 40°C for 60min. The activity was stable in the range of pH 7.5 to 8.5, and maximum activity was occurred at pH 8.0.

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The influence of various nucleotides on the activity of AMP deaminase (EC 3. 5. 4. 6) from skeletal muscle of snapper Pagrus auratus has been investigated. The enzyme was activated by 1mM adenine nucleotides such as ATP and ADP. The substrate-saturation curve of the enzyme was sigmoidal in the absence of effectors, but it changed to a hyperbolic curve through the addition of ATP, ADP, and K⁺. ATP proved to have a biphasic effect on the enzyme, in other words the enzyme was inhibited by ATP at a low concentration of 0.1mM and activated at a higher concentration.
The enzyme activity was inhibited effectively by GTP ranging from 0.1 to 5mM at a substrate concentration of 1mM AMP, and the inhibitory ratio showed a maximum value of 67% by the addition of 0.1mM GTP in the absence of K⁺, while 50mM KCl can essentially reverse the inhibition of the enzyme activity by GTP.
The regulatory property of snapper muscle AMP deaminase activated by ATP is similar to those of the enzymes from the internal organs of animals, the muscle of other fishes, and baker's yeast.

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An optical method using murexide for determining calcium ion concentration at neutral pH could be applied to surimi and surimi paste; walleye pollack surimi used contained 2.76±0.17mM Ca²⁺.
Surimi pastes having different Ca²⁺ concentrations were prepared from the surimi by three different methods and incubated at 25°C prior to heating at 90°C. During the incubation, it was found that the gelation, an increase in cross-linked myosin heavy chains, and an incorporation of MDC into surimi paste occurred in a Ca²⁺-dependent manner. The maximal values for them were obtained in the presence of Ca²⁺ in the range of 2-5mM. Sr²⁺ and Mg²⁺ could not replace Ca²⁺ in the set gel formation.
It is concluded from all experimental results obtained that the major role of Ca²⁺ in set gel formation is the activation of TGase in the surimi paste.

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To elucidate the roles of 5'-nucleotidase in freshness lowering of fish muscle, the effects of some muscle constituents and various substances on the activities of membrane-bound and cytosol 5'-nucleotidase isolated from the white muscle of black rockfish Sebastes inermis were examined. And the activities of both enzymes, nucleotide composition and the K-value of black rockfish white muscle were estimated during postmortem storage at 4°C, simultaneously.
Both enzymes were inhibited strongly by ADP and ATP, and activated by a high concentration (5-10mM) of phosphocreatine. In the muscle of black rockfish, 5'-nucleotidase activity was observed to decrease from the initial value to a minimum at 1-2 days of storage, then to increase gradually to a maximum after 4 days keeping pace with the decrease of phosphocreatine and the rise and fall of ADP. This change in enzyme activity may be assumed to be influenced by the concentrations of these metabolites, and may result in the changes in IMP content and the freshness of fish, viz. the K-value.

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