This report describes fish diets made from dried “tofu” cake (TC), dehydrated garbage fried in waste oil (fried meal; FM) and fish soluble (FS) as raw materials. Two test diets containing TC (12.0%), FM (10.2% and 15.1%), FS (43.0% and 28.0%), fish meal (30.0% and 40.0%), feed oil (3.0%), vitamins (1.25%), minerals (0.14%) and lysine (0.45% and 0.5%) were prepared. After pelleting, the diets were dried in the sun. Quality in the nutrition of the diets was determined by chemical analysis. The effects of the diets on the growth and feed efficiency of cultured red sea breams were investigated.
The crude protein contents on dry matter basis of the test diets were slightly lower than that of commercial red sea bream feed. On the other hand, the crude fat contents on dry matter basis and acid values of the test diets were slightly higher than those of the commercial red sea bream feed, and peroxide values of them were much higher. Except histidine, A/E ratios (essential amino acid/total essential amino acids × 1000) of essential amino acids in the test diets were in the optimum range.
In the feeding test, which was conducted for 91 days at water temperature averaging 23.2°C, the growth and feed efficiency of red sea breams fed on the test diets were nearly equal to that fed commercial feed.
These results suggest that “tofu” cake as food by-product, garbage, and fish soluble as waste from fish product plants, are available for fish diets.

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Mass-production of triploid ayu was performed by the method giving cold or hyperpressure shock on fertilized egg in order to evaluate the growth and maturation of triploid fish. During premature stage, triploid fish showed ordinal growth rate and food conversion efficiency being comparable with normal diploid fish. Female triploid fish continued to grow up well during the spawning season and survived even in the post-spawning season although all of the normal diploid and male triploid fish had already died. The triploid reached to maximum size which was scarcely found in wild fish.

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Spawning of cockles, Fulvia mutica, occurs in spring and autumn in Miyazu Bay, Kyoto. Based on the observation of cockles released from a hatchery in 1987 and 1988 and recaptured in July 1989, some differences in the growth resting band on shells between two broods were estimated for the width of the band and its position on the shell.
During the first year, any resting bands were not marked for the spring broods, while for the autumn broods, rather wide band (8.3mm) was formed at the middle part of the shell. Cockles of the spring broods caught in July of the second year had the band (4.0mm width) at the edge of theshell. From these findings, cockles commercially caught can be identified as spring and autumn broods, respectively.
In order to estimate the time when the band was formed on shells, relations between band formation and monthly changes of sexual maturation and body weight were investigated. It is probable that the growth resting band for autumn broods was formed when high water temperature and maturation occur simultaneously.

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The population of microaerophilic bacteria, along with aerobic and anaerobic bacterla, was investigated in the water and sediment of a goldfish (Carassius auratus) culture pond. Microaerophiles were isolated from the 56% samples in the pond water at densities ranging from3.0×10¹-1.6×10³ CFU/ml and from the 100% samples in the pond sediment at densities of 1.4×10³-1.0×10⁶ CFU/g. These population densities were much less than those of aerobes/facultative anaerobes.
A total of 76microaerophilic bacterial strains were classified, based on 7 bacteriological characters, into 13 groups, alomost of which have yet not been reported.

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The feasibility of vaccination against edwardsiellosis of glass eels of Anguilla japonica was investigated by using passive immunization trials. Passive immunization was performed by immersion of glass eels into solutions of either eel or rabbit hyperimmune sera to E. tarda. Immune protection of glass eels was assessed by water route challenge performed 1, 3 or 5 days after passive immunization. As results, passive immunization with both eel and rabbit hyperimmune sera provided a protection that increased from the 1st to the 5th day post treatment. However, a higher degree of protection was obtained using rabbit antiserum.

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The settlement of larvae and the growth of juveniles after metamorphosis in Haliotis discus hannai were assayed on the each plate covered with microalgae of four species containing natural mixed ones as blank. Three species of microalgae for this experiment were Cocconeis sp., Navicula ramosissima and Nitzschia closterium.
Of the settlement larvae on the each plate, the numbers of settlement larvae were large in the Cocconeis, low in the blank and the Nitzschia, and intermediate in the Navicula. The numbers of larvae on the plates of the Cocconeis were about ten times as many as that of the blank. Of the growth of juveniles was predominant in the plates covered with the Cocconeis among the others.
Therefore, it was considered that the settlement of larvae and the growth of juveniles after metamorphosis were effected remarkably by the species of microalgae attached to the plates.

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The growth of transplanted Laminaria japonica was studied for cultivation on the coast of Naruto in the temperate waters. The young plants were tagged from December to July for three years. During the course of the present study, the water temperature varied from 8-25°C. The maximum length of the blades attained more than 4m in July. The maximum wet weight of them was 1.4kg/individual. The blade width of them ranged 23-25cm in July. The substantiality value ranged 110-120. These values show the cultivated plants have the sufficiant high quality. The Laminaria plants cultivated on the coast of Naruto became comparatively soft blades by boil processing.

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The young thalli of Porphyra yezoensis f. narawaensis is used widely in the industrialized noni culture in Japan, indicates high growth rate were much investigated in noni culture farm of Saga Prefecture facing Ariake Bay. In this study, the growth patterns were observed in detail in each cultural period of 1983 to 1985. The juvenile thalli better grew in the year of lower water temper-atures and higher salinities. Furthermore it became clear that the low salinity conditions before an exposure arrest the growth of the thalli under the nursing culture. This tendency was seen more evidently in the younger and smaller thalli. Under the field culture, their growth often stagnated owing to remarkably changes of the environment of two or three days ago before. The growth pat-tern of the caltural juveniles formed a logistic curve, whose formula derived from the average of three years was expressed by follows;
Lt=242.662/ (1+exp. (-0.261 (t-31.576) ) )
Lt: thallus length (mm) after t days,
t: days.

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The most clear specific differences between two kinds of fresh water salmons, the amago (Oncorhynchus ishikawai) and the yamame (O. masou) are (1) the presence or absence of red spots on lateral side and (2) arrangement of apical circulli of the somatic scale. These differences were also clearly comfirmed between large-sized specimens of the amago and the yamame. As they grow larger than 300mm in standard length, their parr marks disappear and they look like a sea-run form or a lake-run form in external appearance. But they still have morphological characters of a juvenile form in some points, such as the depth of caudal peduncle, size of fins and scale pattern. The large-sized specimens of the amago grow to a standard length of 300-500mm at age 2⁺ or more in rivers or dams, and the yamame about 300mm at age 2⁺ or more in rivers. After spawning female and male are almost dead from exhaustion, but a part of the male population survives.

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The time of first feeding and the influence of the time of feeding initiation on the survival and metamorphosis of the zoeal larvae of Macrobrachium rosenbergii were studied. Zoeae were reared in aquaria with circulated water at 28°C and 10.5‰. The 1st zoeae were not observed to feed when they were fed with Artemia nauplii or rotifers. Molt to the 2nd zoea commenced from 28 hr, with 100% of the zoeae reaching the 2nd zoea by 47 hr after hatching. First feeding was observed from 35-37 hr, with approximately 100% of the 2nd zoeae observed feeding by 61-65 hr after hatching. Five groups of zoeae were fed with Artemia nauplii commencing on the 1st, 2nd, 3rd, 4th and 5th day after hatching, respectively. The survival rate and metamorphosis ratio of zoeae which were fed commencing from the 1st, 2nd and 3rd day showed no significant difference, however they were markedly higher than those fed from the 4th and 5th day. The number of days required to metamorphose prolonged as the time of feeding initiation was delayed. The results of the study indicate that for the most successful development of the zoeae they need to be fed prior to the 3rd day after hatching.

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An attempt have been conducted to improve the culture species of the rotifer Brachionus plicatilis by temperature control and steady-state of feeding.
The two types (L & S) of rotifer were continuously maintained in renewly batch culture in 50 ml flasks. The culture were carried out for 8 months in controlled temperatures 15, 25, 35°C, respectively, salinity at 20 ppt and illumination 2 klux, (15L: 9D) . The alga Nannochloropsis sp was conducted indoors using Yashima medium at 20 ppt. The rotifer culture medium was renewed every 2-4 days depend on each temperature, and special care was undertaken to maintain the food density (18-20 x 10⁶ cell/ml), rotifer exponential growth rate, and asexual reproduction. Every month, rotifer from each temperature treatment was transferred individually to the well of microplate to observe its number of egg laid, offspring produced, reproductive period and individual lifespan. Calculation of population growth rate was made as Theilacker and McMaster (1971) . Simultaneously, some rotifers were mass cultured respectively to collect samples for electrophoretic analyses. Horizontal starch gel electrophoresis was carried out following the procedure described by Taniguchi (1978) . Twelve enzymes were examined following the staining method of Shaw and Prasad (1970) ; Numachi (1970) and Taniguchi and Numachi (1978) .
Results showed that the rotifer have changed concerning its growth rate, sex structure and body size due to longterm adaptation to temperature control and steady-state of feeding. The growth rate of the S type rotifer at each temperature have increased from the average of 0.25, 0.85 and 0.95/day to the average of 0.48, 2.15 and 2.45/day, respectively, and that of L type rotifer increased from the average of 0.65, 0.75 and 0.68/day to the average of 0.98, 1.45 and 2.03/day, respectively. The population lost the ability to produce males. The rotifer at high growth rate were more rotund due to developing internal eggs. The lorica size decreased with increasing the temperature and age of individual rotifer.It suggested that the maintainance of temperature, salinity, changes of culture medium and steady-state of feeding have been able to select and maintain the rotifer population to have a high growth rate and was assumed to have different genotypes than that of the parent population. Results of the electrophoretic analyses showed that several phenotypes of AAT, ACP, and IDHP isozymes were observed in the L type rotifer which have been maintained at those culture conditions at 15 and 35°C for 6 months. However, the differences of phenotype were not found out among those temperatures in S type. This may indicates the fact that the L type rotifer which was naturally called as dominant strain in low temperature, however, have showed high growth rate in the high temperature near to the rate of the S type. It suggested that the used of rotifer which had been adapted for high growth rate should increase the rotifer production efficiencies in it mass cultures.

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The present experiments were conducted in order to investigate the “algal growth potential” (AGP) of the fish farming sediments indicated by the culture of Nannochloropsis sp. Sediments were collected by the traps in the “fish farm” (Fish F.) and “non fish farm” (Non F. F.) at neap tide between June, 1989 and september, 1990. Inorganic nutrients extracted from 5 g-wet sediment in 350 ml sea water were analyzed, and then were measured the AGP for Nannochloropsis sp.
Average quantities of the sediments were 51.6 g-dry⋅m^-2⋅day^-1 in fish farm and 34.4 g-dry⋅m^-2⋅day^-1 in non fish farm. Average quantities of the organic sediments were 15.8 g-dry⋅m^-2⋅day^-1 in fish farm and 5.2 g-dry⋅m^-2⋅day^-1 in non fish farm. Higher quantities of organic sediment were observed in fish farm in October and November, 1989 when the juvenile of red sea bream were fed on moist pellet. Higher ignition loss of 38.8% was measured so on. Lower ignition loss of 27.5% was observed during June, 1989 and September, 1990 when the adult yellowtail were fed on frozen fish.
Higher Nannochloropsis production rate of 46.8×10⁶ cells⋅ml^-1 was obtained when the adult yellowtail was fed on the frozen fish in fish farm. During those period, average quantities of IN and IP of the extracts were 432.3μg-at⋅l^-1 and 96.1μg-at⋅l^-1, respectively. Lower Nannochloropsis production rate of 31.7×10⁶ cells⋅ml^-1 was measured when the red sea bream were fed on moist pellet. During those period, average quantities of IN and IP were 530.8μg-at⋅l^-1 and 14.7μg-at⋅l^-1, respectively. It is considered that IN/IP ratio in the sedimet extract might be more important factor for the AGP rather than the amount of inorganic nutrients.

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Eggs collected from broodstock tank were used to determine the effects of water temperature on the embryonic development under the laboratory condition.
The embryonic development was prominently influenced by incubation temperature. The integrated temperatures till hat7ching were approximated as being 820, 670, 628, and 644°C⋅hrs at 20, 23, 25, and 28°C, respectively.
Eggs hatched at the temperature ranged from 20°C to 34°C. The development was stopped at 15°C and hatching was not normally proceeded at 34°C. The incubation temperature at 25°C showed the best hatchability and the lowest abnormality of hatched larvae.

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The effects of salinity and light intensity on the growth of young Saygassum ringgoldianum from Kominato, Chiba Prefecture, central Japan have been studied in laboratory culture.
Young thalli were cultured under six salinity levels (salinity 5, 10, 15, 20, 25, 30), and three light intensity levels (1000lux, 5000lux, 10000lux) with a 12 L: 12 D photoperiod, 20°C, in PESI medium. One-week-old plants cultured at 20°C, 12 L: 12 D, 6000lux were transferred to each condition tested.
The thallus length increased with salinity at all light intensity levels. Although they grew with light intensity increase at salinity 30 and 25, there were no apparent differences on the growth between three light intensity levels below salinity 20. Young thalli grew very slowly at salinity 10.They bleached at salinity 5.

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Effects of a short-term thermal shock on the developing fish eggs were investigated using the pond smelt Hypomesus transpacificus (Japanese name; Wakasagi) .The eggs were exposed to nine test temperatures (Δt=14-30°C) for 15min at 30 different stages, and returned immediately to the initial incubation temperature (10.0±0.3°C) . From the results of hatching rate, median hatchable shock temperature (MHST) was calculated for both total and viable hatch at every tested stage.
Both MHSTS depended on the developmental stage at the time of the shock, and were lower at the early cleavage stages from the 32-cell to the late morula and at the blastopore closing stages than at any of the others. Namely, the eggs at these two stages were the most susceptible to the short-term thermal shock. A relatively high frequency of abnormal larvae with a tail of wrinkled membrane fin appeared during the period from the retina pigmented stage to the just before hatching stage.

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Endocrine-like cells were observed in the digestive tracts of the oriental goby, Acanthogobius flavimanus, by light and electron microscopies. These cells show positive staining with lead haematoxylin. Tests for argentaffin and chromaffin reactions are generally negative. The endocrine-like cells always scatter in the mucous epithelium. These cells have many secretory granules in the cytoplasm. The two types of endocrine-like cells (I and II) are identified by the locations in the mucous epithelium and the morphological characteristics. In Type I, the basal part directely faces the basement membrane and also the apical part reaches the digestive lumen. Microvilli are always recognized in the luminal surface of the cytoplasm. Endoplasmic reticulum and Golgi apparatus are mainly found in supra-nuclear region and many endoplasmic vesicles including the secretory materials often recognized in the cytoplasm. The secretory granules are in the immature stage at the basal and middle parts of the cytoplasm while the mature granules are distributed in the subsurface. In addition, the cytoplasm has the endoplasmic lamellar structure which is a general characteristic of fish intestinal epithelium. It is suggested that the endocrine-like cells mutated from the mucous epithelial cells. Type II is usually located in the basal part of the epithelium and lies parallel with the basement membrane. The immature secretory granules always found in the cytoplasm. In the two endocrine cell types, the cell membranes at the base and the sides do not show complex interdigitations between neighboring cells, but desmosomes occur sporadically in these portions. In the present study, it was not found that the secretory granules are released into the connective tissue or intercellular space by emiocytosis.

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This study was intended to clarify the process of decomposition of particulate matter (PM) and particulate organic nitrogen (PON) of biodeposits obtained from a recycling culture system (artificial ecosystem culture) of rotifer Brachionus plicatilis, in order to consider reutilization of biodeposits in the culture system as nutrients for recycling phytoplankton culture. Culture methods of rotifer was mentioned in the previous report. Biodeposits collected from rotifer culture tank, were decomposed in a tightly stoppered plastic bottle at 21±1°C for around 60 days. Supernatant was exchanged with new seawater every 3-8 days, to determine dissolved total nitrogen concentration. Residual weight of PON was obtained by subtracting the weight of total dissolved nitrogen from the initial residual weight of PON.
It was concluded that the PM and PON consisted of three fractions: the first, easily decomposable fraction (fraction I ) ; second, decomposable fraction (fraction II) ; and third, refractory fraction (fraction III) . The biochemical decompositions of fraction I and II were mathematically expressed by a first order reaction. The progress of decomposition of PM and PON may be mathematically expressed as the sum of two first order reactions and constant value of fraction III.
The rate constant for decomposition of fraction I, which was decomposed within about 10 days of the experimental period, was higher in the PON (0.20 and 0.20) than in the PM (0.085 and 0.13) . However, the rate constants of fraction II, which was decomposed throughout the experimental period, were the same value in both PON and PM (0.022 and 0.015 for PON, and 0.018 and 0.018 for PM) . The fraction III of PM and PON remained constant at 60% and 50% of initial values, respectively.

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