We have studied both quantitatively and qualitatively the digestive-tract contents and the seasonal changes of plankton production in relation to the food intake. The materials and data were collcted from several fishing grounds on the coast of Kyoto Prefecture. The results obtained are:
1) The amount of the stomach and intestine contents was found small in the early morning and great in the evening. The plankton taken as food during the daytime might be digested until the next morning. It has been suggested that the feeding intensity attained to a great extent in the daytime but the feeding almost ceased in the night. Thus it may be concluded that the sardine follow a feeding rhythm during the course of a day.
2) Examining the stomach and intestine contents of the sardine caught in the Bay of Maizuru on Dec. 18 (1953), we found that the important plankton components were Skeletonema costatum and Thalassionema nitzschioides. Especially the hard-bodied frustules of the latter might little decompose in the stomach and intestine, and hence they were comparatively easy to evaluate. Using these two diatoms, estimations were made of the number of cells reserved in the digestivetracts and also of the plankton density in the water. From these investigations, how much water should be used each day for the straining of plankton was calcuated. A sardine of 12.0cm. long should take water of ca. 270 litres per day, and the fish could strain the plankton of ca. 270•P (P: number of plankton per litre) from it. In comparison with the data obtained from the sardine of different length, it was deduced that the volume of strained water as well as the food intake was nearly proportional to the square of body length.
3) The analyses of the digestive-tract contents of the sardine and the investigation of the plankton composition in the waters showed a considerable confluence. The sardine indicated little selectivity of food. So far as the food selectivity is concerned, it will be further discussed in the next paper from the standpoint of the feeding mechanism.

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For estimating the density of fish population, catch per unit of effort is commonly used. But in order to allow such a method, distribution pattern of fish should be researched.
In a fishing ground, distribution of individuals and schools would be not random but contagious distribution. Frequency distribution of catch of many species is represented well by P_ÓLYA-E_GGENBERGER type. And by transformation
x'=k^-1/2sinh^-1(kx)^1/2
where k is constant, the standard deviation approaches a constant without regard to the mean. By this method, we can compare the groups with each other or examine the correlation of them.
In this examination, catch of th ?? demarsal fish in the East China and the Yellow Seas was used.

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Some individuals among carps of one batch grow much faster than other in the same condition. We call them “Tobi-Koi” or Shoot-carps. They show characteristic asymmetry on the frequency curve of the body length of the batch. We calculated the skewness
Sk=1/σ³•1/N•∑f_i(x_i-^-x)³
and found that its value is larger than +1.5 in many cases in which the Tobi-Koi appears.
The frequency curves of the egg diameter, body length of hatched larvae and 8 days old post-larvae kept without feeding show approximately the normal distribution, but after 20 days culture fed with Cladocerans the Tobi-Koi individuals are found already.

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With regard to ecological characteristics of the carp and the crucian carp when used as objects of loosely diffused culture, the present study was carried out to compare them with each other.
(1) Survival rate of the crucian carp is always higher than that of the carp, and yearlings of the crucian carp grow faster than the other in such circumstances as without sufficient food for them.
(2) While there occurs unevenness of growth among the batch of carps, the crucian carps grow always rather evenly.
(3) The difference of the feeding habit of the two species is considered as one of the main causes of above mentioned phenomenon. The carp feeds mainly on comparatively large bottom fauna (Chironomus larva etc.), but the other depends on the so-called “Aufwuchs” (minute adherent organisms), algae and organic detritus, namely matters as available to the crucian carp are more ubiquitously present than those for the carp.

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Fisheries of “iwasi” in the Inland Sea have been, in the previous report, classified into three types by analysing secular variations of yield as problems of time series and corelogram. In this report, the writer treats fluctuations of catch in each type with relations to factors of environments-oceanographical and meteorological conditions.
Patterns of annual variations of sea water temperature and specific gravity at several stations may be characterized by parameters of the patterns, as shown in Tables 1, 2, 3 and 4. In Tables 5 and 6, are shown coefficients of correlation between fluctuations of catch in each type and factors of environments.
And moreover, problems of predictions have been discussed in the point of view of interpolation by correlation diagram and extrapolation by corelogram. Fig. 1 shows the correlation diagr m between x, fluctuations of catch in type 1, and parameters b, coefficient of linear regression of specific gravity obtained at Kasaoka every two years before the period under consideration. Because of this relation, values of x are possible to be estimated from value of b two years before by means of interpolation.
In Figs. 2, 3 and 4, full and dotted lines, show secular variations of actual catch and calculated values by means of extrapolation from corelogram of time series, respectively. Shaded parts indicate confidence intervals of about 70%.
Above-mentioned relationships have been discussed only in static and apparent states of phenomena. However, dynamical treatments of relationships between parameters of aquatic resources, as well as research upon cause of discrepancies between actual and predicted values of catch, are important subjects which will be studied in future.

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Sand stones, and pyramidal and prismatic concrete blocks were set as the cellecters of Geliaium in the sea off the coast of Tokushima pref. in July, September and November, 1953.
Some of the collecters were recovered by divers for exammination on June 1, 1954. and the weight of Gelidium growing on each collecter was recorded. The data was analized statistically with the following results.
1) The weight of attaching Gelidium did not differ significantly on the stone and the collecters.
2) Gelidium was found attaching on the collecters set in the three different months. Attachment was richest on the collecters set in July, and poorest on those set in November.
3) Geliaium attached on collecters far more abundantly on the shore facing the west and south than on the shore facing other directions.
4) Selecting suitable sites, therefore, is most important in propagating Gelidium by setting collecters.

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In the sea as a whole the combined activities of bacteria and allied microorganisms tend to create environmental conditions which are conductive to the growth of plants and animals. However, in localized regions certain types of microbiological activities may be inimical to the well-being of other organisms.
An outstanding example of the antibiotic activi ?? ies of bacteria in the sea is the production of sulfide in quantities which are toxic to both animals and plants.
It is already known that a considerable amount of sulfides often occurred in stagnant bodies of coastal waters which received a large amount of industrial or municipal drainage.
The sulfides occurring in the sea may partly result from the anaerobic decomposition of albuminous compounds. More is believed to result from the bacterial reduction of sulfate.
Although a few papers concerning the determination of sulfides which occurred in the sea have been published, it appears that few workers have studied the occurrence and the activities of sulfate-reducing bacteria in the sea in relation to the pollution of coastal waters up to the present.
Such being the case, the present series of study were undertaken with the aim of elucidating the factors which participate in the sulfide production by bacteria in the sea, with special reference to the influence of the inflow of pulp mill drainage upon the sulfide production in the coastal regions of the sea.
The present paper embodies our ecological observations carried out in Hiroshima Bay. Many samples of sea water and bottom mud were collected from different depth at various stations in Hiroshima Bay (Fig. 1), and immediately the number of sulfate-reducing bacteria was counted by means of the extinction dilution method. In addition to the bacterioloigcal examination, the chlorinities of water samples and the amounts of C. O. D., ignition loss, total sulfides and free H₂S of mud samples were determined. And also the temperatures of all samples were recorded.
Results obtained are as shown in Tables 1, 2 and 3 and may be summarized as follows:
1) Relatively small number of sulfate-reducing bacteria were evenly distributed in the sea water regardless of the depth of the water, the distance from land or the amount of terrigenous pollution.
2) Larger number of sulfate-reducing bacteria were found in bottom mud at nearly all stations examined. The number of sulfate-reducing bacteria contained in bottom mud was correlated with the sulfide content of the mud as shown in Figs. 2 and 4.
The result suggests that the greater part of the sulfides contained in the mud were produced by the sulfate-reducing bacteria.
The distribution of sulfate-reducing bacteria in bottom mud or the sulfide content of bottom mud was directly correlated with the organic content (Figs. 3 and 5), but not correlated with the distance from land or the depth of the overlying water. As shown in Fig. 6 the population of sulfate-reducing bacteria in marine sediment was presumably more largely dependent upon the quality-decomposability-of the organic matter than upon the total quantity of organic matter present.
It is thought that a large amount of easily utilizable organic matter brought onto the bottom mud by the industrial drainage, such as pulp mill waste, may vigorously accelerate the activity of sulfate-reducing bacteria present in the bottom mud of the coastal regions of the sea.

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The present paper is concerned with the influences of temperature, pH value and salinity upon the sulfate-reducing activity of marine sulfate-reducing bacteria.
It is thought that these environmental factors are primarily affecting the development of sulfides in the bottom mud of coastal regions of the sea receiving a large quantity of industrial drainage from pulp manufactories¹⁾.
It was therefore hoped that the infor ?? tion obtained would provide a better understanding of the sulfides production in such regions of the sea, about which very little is known at present.
The development of sulfides in the sea water medium inoculated with the pure culture of marine sulfate-reducing bacteria was observed at various temperatures, at various pH values and at various salinities.
The results obtained are shown in Figs. 1, 2, 3 and 4, and may be summarized as follows:
1) The marine sulfate-reducing bacteria grew well over the range 20-40°C but failed to grow at 15.5°C and 45°C. The op ?? imum temperature for the production of sulfides was at about 35°C. Below 35°C sulfides were more vigorously produced with raising of temperature.
2) The sulfate reduction by this organism occurred within relatively narrow pH range 5.8-7.5. The maximum production of sulfides resulted at pH 6.5.
3) The sulfate reduction by this organism occurred over the relatively wide range of salinity 1.5-6.1%. The maximum development of sulfides was obtained in the medium having a salinity of 3%.

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Influences of oxidation-reduction potential and various kinds of metalic ion upon the activities of marine sulfate-reducing bacteria were preliminarily studied. These enviromental factors are presumably affecting the development of sulfides in the bottom mud of the sea, and it is thought that the knowledge concerning this problem may be of use in the solution of the problem of the industrial pollution in the coastal waters.
The effect of oxidation-reduction potential upon the development of the sulfate-reducing bacteria was studied, using the media containing L-ascorbic acid in various concentrations, by means of the pureculture, the mixed culture and the crude curlture.
The results obtained are shown in Table 1, and may be summarized as follows:
(1) In the form of pure cultures, the marine sulfate-reducing bacteria could not develop in the media which contained L-ascorbic acid in the concentrations of less than 10mg./L.
(2) In the cases of mixed cultures or crude cultures, the marine sulfate-reducing bacteria were able to develop in the media containing no L-ascorbic acid. It is thought that in the cases of these cultures, aerobic bacteria existing together with the marine sulf ?? e-reducing bacteria in the media had previously prepared the anaerobic conditions for the growth of the sulfate reducers.
(3) The initial stationary period of the growth of the sulfate reducers was progressively shorter with the increasing of concentration of L-ascorbic acid in the media.
Using medium 2 as the basal medium, stimulative and inhibitory effects of Fe⁺⁺, Mn⁺⁺, Zn⁺⁺, Co⁺⁺, and Cu⁺⁺ upon the sulfate-reducing activity of the marine sulfate-reducing bacteria were studied by the pure cultures.
The results obtained are shown in Figs. 1 and 2. As may be seen, when a considerable amoun ?? of Mg and a tra ?? of Fe were contained in the cultures, the development of sulfides was stimulated by the addition of Fe⁺⁺, and somewhat or completely inhibited by the addition of Mn⁺⁺, Zn⁺⁺, Co⁺⁺ and Cu⁺⁺. No antagonistic action of Mn⁺⁺ upon Fe⁺⁺ was observed in the sulfate-reduction.
Using the basal medium which was perfectly deficient in Mg⁺⁺ and Fe⁺⁺, the metalic ion growth requirements of marine sulfate-reducing bacteria were studied by the pure cultures.
The results obtained are shown in Tables 2 and 3 and may be summarized as follows:
(1) Mg⁺⁺ and Fe⁺⁺ were essential for the development of the marine sulfate-reducing ba ?? cria.
(2) The concentration of Mg⁺⁺ required for the growth of the marine sulfate-reducing b ?? teria were somewhat higher than that of Fe⁺⁺.

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During the course of an investigation on the digestibility of the protein in diets, our attention was attracted to the NH₃-N, and urea-N excreted by carp and goldfish.
This work was undertaken to determine quantitatively these substances excreted under several different conditions: A-Fish were fed in an approximately air-saturated water; B-Similar to A, but in a water deficient in O₂; C-Starved in O₂ suffcient water; D-Starved in water deficient in O₂
The results obtained were as follows:
(1) Under the normal condition (A), the form of the nitrogen excreted seems to be essentially NH₃-N (Table 3).
(2) When the fishes were kept starved or in a water of low O₂- content for a long time (B, C, D), urea-N excreted increases in amount (Table 1, 2, 4).

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Authors found that the phthalein value of dead fish decreased gradually with the time, suggesting the possibility of estimating the time elapsed after the death.
The me ?? surement of Phthalein value was proposed by H_ATTORI and A_KIBA for determining the toxic strength of Tapes philippinarum and its principle consisted in the determination of maximum dilution where the red color restored when the reduced phenolphthalein-KOH solution, 30 per cent acetic acid solution and 3 per cent H₂O₂ solution were added to the aqueous extracts of muscle. Volatile basic nitrogen, pH and putrid odour as well as P-value were measured on various living fishes, molluscs and crustaceans.
1. The P-values of fishes obtained immediately after the death varied with the species ranging from
2 to 10 (Tab. 1).
2. At about 0.1 of P-value the fishes were seemed to be putrefied (Tab. 2).
3. In case of molluscs and crustaceans, initial P-values were larger than those of fishes and the rates of lowering were smaller.

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A few substances and extractive nitrogens in bloody muscle were compared with those in ordinary muscle of a few kinds of red muscle fish. The reults are as follows:
1) The moisture, total nitrogen and trimethylamine oxide nitrogen are less in amount in bloody muscle.
2) Nitrogens of extractive, diamino fraction and arginine-histidine fraction are less in amount in bloody muscle. The difference of these nitrogens between bloody muscle and ordinary muscle is considered to be due to the poorer amount of histidine in bloody muscle.
3) The monoamino nitrogen has been found to be larger in amount in bloody muscle. But the content of the monoamino nitrogen seems, according to the author's sprevious experiments, to relate inversely to the taste of red-muscle fishes.

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On purpose of utilizing fish-wastes to cattle fodder or fertilizer, we have tested to preserve them mixed with varioos kinds of ground cereals, their offals, and saw-dust. As the results, we have found that broken rice, wheat, corn, rice-bran and wheat-bran have more powerful antiseptic properties, while rice-hull and saw-dust are less in the ability.
We have considered that the preserving power of the latters is due to a mere physical action which reduce the percentage of moisture in the mixture, on the other hand, some chemical substances, in the formers, should be chemically served for antisepticizing in addition to the physical power.

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It was found that the pH value in fish-waste mixed with cereals and their offals which have shown intense antisepticizing power was reduced in the course of storage. If sugars are added to vast mixed with saw-dust which has shown less antisepticizing power, the pH value of their mixtures may also diminished, and increase in the antisepticizing effect may be observed, The antisepticizing effect of cereals and their offals is therefore pursumed to be due to the formation of acids from sugars in them. But as the volatile base nitrogen never increase in quantity in the waste mixed with sugars, in spite of rising of pH value in the final stage of course of storage, the antieepticizing action of sugars should not be regarded to be attributable only to lowering of the pH value,
Starch was found to have scarcely any antisepticizing effect at least in the initial course of storage, but at the presence of sugars, it seems to help their action. Cereals and their offals may correspond to the case.

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