In Alaska, salmon fisheries are restricted strictly to obtain the maximum sustainable yield. But the reproduction situations of salmon resources which are the scientific basis of fishery management are not cleared with a little exception of the study for red salmon.
In this paper, the reproduction situations of pink salmon resources both in Central Alaska and Southeastern Alaska are studied separately in odd year and even year class groups, using the Ricker's formula (R=aEe-^bE).
To estimate the reproduction curves for each stocks, numbers of escapements and returns are estimated from the catch statistics under the adequate assumption, for fishing rate.
Following tables and figures resulted from above estimations show that the recent decrease of catches in Central Alaska and Southeastern Alaska may have been brought about by the decrease of escapement and the fall of reproduction rate respectively.

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The reproduction situation of chum salmon in Alaska has not been studied because of its lowest economical value and small size of stock. However, it has a important meaning to estimate the effect of artificial propagation for chum salmon in Japan and also it is neces-sary to know the situation of fishery management for chum salmon in Alaska.
In this paper, the reproduction situations of chum salmons both in Central and Southeast-ern Alaska are studied using Ricker's formula (R=aEa-^bE), in which the numbers on es-capements (E) and returns (R) are estimated by the catch statistics from 1920 to 1961 under the adequate assumption of fishing rate, which is 0.5 for Central Alaska and 0.5-0.65 for Southeastern Alaska.
Following tables and figures resulted from above estimations show that 1) the number of returns per spawner in MSY is about 3.2-3.6 fishes, and 2) the reproduction situation in South-eastern Alaska has fallen since 1950, while 3) the recent exploitation in Central Alaska does not realize full utilization.

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This report dealt with the bathymetric change of the frequency distribution of daily hauls per boat in relation to the daily catch found in the daily reports of 22 Danish seiners of one of the fish-meal fleets fishing in the Bering Sea during an entire season in 1963. The tendency of increase in daily catch manifested, as stated in the previous reports¹⁾²⁾, the necessity of discussion on the bathymetric difference in the daily hauls per boat being stratified according to the grades of daily catch. And the further stratification of the same records analyzed in the previous reports into the four grades of daily catch per boat of 10 ton intervals (the records were already stratified according to the fishing areas and the fishing depths of 10m intervals) made it possible to get the following findings:
1. In most of the groups of samples, the frequency distribution of day-and-boats with respect of the number of daily hauls per boat plotted against (11-χ) on logarithmic scale was agreeable to the normal series (where a boat conducted χ hauls a day), although those of some of the groups were thought to be the modification of this type and those of the others with good catch were normalized. These facts suggested that the above-mentioned type may be indicative of daily hauls per boat of the Danish seiners probably with the uniform per-formance fishing in the same depth zones of the same areas.
2. The groups of samples yielded the same grades of daily catch per boat showed the tendency of decrease in daily hauls per boat with increase in fishing depth; this tendency was very conspicuous in Area A, whereas very faint in Area C. It became, therefore, clear that the same tendency found before the stratification of the records according to the grade of daily catch was not the false one owing to the bathymetric difference in daily catch but the probably essential one owing to that of some other factors of significance.
3. The groups of samples in the same depth zones showed the tendency of decrease in daily hauls per boat with increase in daily catch per boat, although the boats repeated to haul the net on the days yielded the catch of 10 to 19 tons a boat as frequently as or less frequently than on the days yielded the catch of 20 to 29 tons a boat.
4. The standard deviation of daily hauls per boat seemed to change dependently of either the fishing area or the fishing depth, but that of the samples in the same depth zone of the same area was similar to one another regardless of the grade of daily catch per boat.

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In the previous paper⁴⁾, it was pointed out by experiments with 4 filters of Suma Aquarium of Kobe City that the oxygen dissolved in breeding water was considerably consumed during its passing through the sand beds, and that there was a close correlation (coefficient=0.97) between the oxygen consumption and the BOD decrease during filtration.
The oxygen consumption during filtration (abbreviated to OCF) seems to be due to biochemical oxidation by the microorganisms propagating in the filter. The present studies have been carried out in order to know whether OCF can be used as an index in evaluating the degree of purification of breeding water by filtration. For this purpose, special experimental filters were designed (Fig. 1), to which the breeding water of Surna Aquarium was introduced.
The results obtained are as follows.
1. There is a close correlation (coefficient=0.63) between OCF and the BOD decrease during filtration of breeding water through sand layers of various depths (Fig. 2).
2. During filtration of breeding water, ammonia decreases in concentration in response to depths through which the water is filtered through sand layer (Fig. 3). Since this decrease may be almost attributed to nitrification, on the assumption that the change in the concentration of ammonia and nitrite during filtration are only due to the oxidation of ammonia, the oxygen consumption by nitrification can be estimated from this change. The relation between calculated oxygen consumption by nitrification and depth of sand layer is similar to that between OCF and sand depth (Fig. 4).
3. Deduced from the data thus calculated, the oxygen consumption by nitrification occupies 34% of OCF in experiment 1, and 53% in experiment 2 (Fig. 4).
These results confirm that OCF can be used as a satisfactory index in evaluating synthetically the degree of purification of breeding water by filtration.

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In the previous paper¹⁾, it was confirmed that the oxygen consumption during filtration (OCF) could be used as an index indicating the degree of purification of breeding water by filtration. By using OCF as an index in evaluating the degree of purification, the present studies have been carried out to investigate influences of the filtering velocity and the depth of sand layer on the ability of a filter to purify breeding water.
In general, the BOD data well fit the equation of a first-order reaction. Since OCF as well as BOD is due to biochemical oxidation, it may be possible that the OCF reaction fits the theory of chemical reaction. When compared the OCF data obtained by filtration of breeding water of Suma Aquarium with a first and second-order reaction, it was found that they fitted much better to a second-order reaction formula than to a first order reaction formula (Fig. 1, Table 1).
The time taken for the water passage through the sand layer is correlated directly with OCF (a degree of purification), and the relation of OCF to the depth of sand layer is not direct but only in appearance, since the time taken for filtration is proportion to the depth (Fig. 2).
From the results of the experiments carried out to know the factors which fit the OCF reaction to second-order reaction, it has been deduced that one of the factors may be the distribution of microorganisms in a filter. They are distributed more abundantly in the upper layer of the sand bed than in the lower layer. The ammount of them in each layer of a filter may be determined by the quantity of unoxidized organic materials in the water which flows through that layer. According to the facts mentioned above, the relation of OCF (y/mg/l) to the filtering velocity (Vcm/min) and to the sand depth (Dcm) are shown by the following formula. 1/y=1/C₀+1/C₀²kD
were Co and k are constants, determined by the condition of breeding water.

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The culture of the “Kuruma” prawn, Penaeus japonicas BATE, has been carried on in various districts along the coasts of the Seto Inland Sea.
In the culture pond of the “Kuruma” prawn, remodeled from the unused salt field or enclosed with stretching wire net along the sea coast, it is frequently experienced that the bottom materials are in a reduced state, owing to the accumulation of organic matters such as food-remnants, excrements etc., and that the reduced materials produced in this state have sometimes an injurious influence on the prawns cultured there. The conditions of the materials are evidently determined by diffusion of oxygen from the sea water and sedimentation of organic matters, on the one hand, and by reduction processes of biochemical origin in the mud, on the other.
Many studies concerning the bottom mud of the culture pond have been carried out along the lines of separate chemical or physical analysis of each factor forming the environment without systematic or causal connection. However, it may be of most importance to examine the quality of bottom material as a whole, for indicating the criterion about the degree of deterioration of the culture pond. No clear idea of the biochemical transformations in bottom materials can be gained without a consideration of the redox potential.
From these points of view, the present study was designed to clarify the oxidized and reduced phase of the bottom materials by means of measuring the redox potential in the Aji Prawn farm (Fig. 1). However, this quantity will give only a measure of intensity.
Undisturbed cores were obtained and potential, pH value, organic carbon content and total nitrogen content were determined from the mud in various layers down to 22cm below the mud-water interface. Comparisons of redox potentials in summer with those in winter were made and then the potential of various mud layers below the mud surface was related to the quantity of the organic carbon and the total nitrogen, respectively.
The results obtained may be summarized as follows:
(1) The redox potential (corrected to pH 7) in the top layer (0-8cm) corresponds to -0.01 to +0.09 volt in August, and to +0.18 to +0.21 volt in March. Potential at about 20cm below the interface lies at about +0.27 volt throughout the entire annual cycle (Table 1, Fig. 5).
(2) Near the surface (0-8cm) the potential is correlated with the quantity of organic matter, but in deeper layer no correlation is recognized between both (Fig. 3, 4).
(3) Except on occasion at its surface the mud at the bottom of pond has reducing pro-perties in August. There is a rise of potential as far as 20cm into the mud. In March, the potential falls slightly with depth and then rises from 0.18 volt at 6cm to +0.27 volt at 14cm. Within the range of the depth 14-20cm, there is little change (Fig. 5).
(4) The high potential obtained at about 2cm below the interface in March suggests that the mud at this depth is recovered from the reduced state; the potential lying at about -0.01 volt in August rises till in March a value of +0.21 volt is reached (Table 1, Fig. 5).
(5) A very thin, flocculent, brown precipitate, or oxidized microzone, was seen dimly in August and clearly in March, so that the potential in superficial layer of mud would have shown the high value.

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In the present paper the author has qualitatively and quantitatively analysed the feeding habits of the sea bream, Chrysophrys major TEMMINICK et SCHLEGEL, with special reference to the daily change of the feeding activity, based on the stomach contents of the 856 individuals, which were caught by bull-trawler at the 352nd official block in the Yellow Sea, during the period from November 18 to 19 in 1964. These samples were obtained continuously (Table 1, Fig. 1). Summarizing the results of the investigation, three conclusions were derived as follows:
1) As the results of the qualitative and quantitative analyses, it was recognized that the small macrura was the most important food organism of the young sea bream (Table 2, Fig. 2).
2) The degree of digestion of the food found in the stomach was high during the night and low in the daytime (Fig. 3). The fish caught in the daytime has more stomach contents than that caught during the night (Fig. 4).
3) The above facts suggested that the young sea bream take their food during the morning and the food taken may be digested until the next morning. Thus, it may be concluded that the young sea bream follows a feeding rhythm during the course of a day.

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Scales of adult sockeye salmon migrants were collected from 19 rivers along the coasts of the northern Pacific (Fig. 1).
These scales were magnified 100 times and the scale character ‘FR’, distance between the nucleus and the last annulus of the fresh water zone along the symmetrical axis, was compared among these fish groups.
From the comparisons of the scale character, the characteristic of Bristol Bay's race was established in both cases of 5₂ and 6₃ aged fish groups. Therefore, an attempt to estimate the percentage of the Bristol Bay's race of sockeye salmon in the western high sea area of the northern Pacific was done, and the following results were obtained.
1) Age of sockeye salmon caught in the western high sea area of the northern Pacific are 4₂, 5₂, 5₃, 6₂, 6₃, 6₄, 7₃ and 7₄. Among such aged fish, 5₂ and 6₃ aged ones are most abundant and totals of the fish of these two ages occupy more than 70 percent in every fish group (Table 1). 5₂ and 6₃ aged fish groups, therefore, were studied.
2) The mean values of the scale character ‘FR’ of the 5₂ aged sockeye salmon migrants collected in rivers are ranged from 0.37 to 0.49mm in fish groups of Bristol Bay and from 0.20 to 0.37mm in most fish groups of Asia and other two areas, Gulf of Alaska and America-Canada (Table 2, and Fig. 2, 3).
Those of the 6₃ aged fish are from 0.57 to 0.69mm in fish groups of Bristol Bay and 0.35 to 0.53mm in most fish groups of the other areas. Therefore, the local race, Bristol Bay's one, can be recognized through its scale characteristics in both cases of 5₂ and 6₃ aged fish groups.
3) Frequency distributions of the scales character “FR” of groups of 5₂ aged sockye salmon caught in the western high sea area of the ocean contain some fish groups with larger mean values than 0.37mm, which are the characteristic of the Bristol Bay's race, and fish groups with smaller mean values than 0.37mm, which are the charac-teristics of fish of Asia and other two areas. On the other hand, frequency distributions of the scale character of groups of 6₃ aged sockeye salmon caught in the high sea are near the coast of Asia contain few fish groups with larger mean values than 0.57mm, which are the characteristic of the Bristol Bay's race, though those of fish groups caught in the mid ocean contain some ones of Bristol Bay's race.
4) Some 5₂ and few 6₃ aged sockeye salmon of Bristol Bay's race which appear in the high sea area near the coast of Asia were bred in 1956 and 1955 respectively. Abundance of appearance of the Bristol Bay's race of sockeye salmon in this sea area, therefore, differs by year in relation to abundance of its fry production of each year.

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1. This report dealt with the distribution of groundfishes hooked along a gang of setline of ca. 13.7km long laid on April 30, 1962, from 60°47'N to northward along the 179°48'E line.
2. The tendency of bathymetric difference in the density of the groundfishes was found even in the distribution of them hooked along a gang laid on a very easy gradient sloping from 280m to 370m deep, although this tendency did not take the form of simple gradient of density being modified seriously by the schooling habits of fish.
3. Usually, the groundfishes, especially those of high economic value, were distributed more densely along the outer edge of the plateau than in other zones, but the present example provided with no evidence in support of such a structure as this.
4. This suggests that the very obtuse inflection of bottom gradient like this may not be the symptom of a good locality of setting the gears, because the weak inflection like this was not enough distinct to modify the distribution of the groundfishes.

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In continuation of the studies on the effects of marine products on the cholesterol me-tabolism some more species of green and brown algae were screened. The different species of the algae were dried and pulverised and incorporated in the diets at 5% level with exo-genous cholesterol and fed to the rats for 5 weeks ad libitum.
It is observed that the plasma cholesterol level in the rats fed with green algae such as Ulva pertusa, Enteromorpha prolifera, and Monostroma nitidum was lower than the plasma cholesterol level of the rats fed with brown algae such as Laminaria sp., Hijikia fusiformia, and Undaria pinnatifida. These observations are in agreement with the earlier conclusion that the green algae showed a positive effect in reducing the plasma cholesterol level in the rats as compared with the brown algae. The brown algae did not show any effect in re-ducing the plasma cholesterol level.

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Trimethylamine or dimethylamine can hardly be the precursor of formaldehyde, biologically appearing in the tissues of some fishes related to gadoid group.
As a most probable route of biological formation of formaldehyde and dimethylamine in fish, oxidation-reduction enzyme system was proposed by presenting an example of methylene blue which evidently enhanced the reaction.

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The fresh beef liver has been considered to be an excellent diet for rainbow trout (Salmo irideus) fry. Although several investigations have been published on the effect of liver on chicks or rats, very few publications appeared concerning the growth stimulating activities present in the fresh beef liver for fishes. This investigation was attempted to elucidate the growth stimulating substances for rainbow trout fry. The fresh beef liver was fractionated into three fractions with sucrose solution and each fractions were analyzed on amino acids and vitamins (Fig. 1 and Tables 3 and 4). To evaluate the role of vitamins, Halvers vitamin mixture, each fractions and three kinds of vitamins mixture prepared on the basis of analy-tical data (Table 4) to imitate the corresponding fractions were incorporated into the basal diet (Table 1), and fed to the rainbow trout fry, as shown in Tables 6-8. The growth response of fish suggests that the vitamins examined here may not be the growth stimulating substances in the fresh beef liver.

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1. The compound isolated from starfish, Asterina pectinifera, was identical with D-cysteinolic acid which was obtained from seaweeds by previous workers.
2. Amberlite IR-4B was pretty effective for the separation of taurine and the compound.
The authors are grateful to Dr. M. Fujino, Laboratory of Takeda Chemical Industries, Ltd., for elementary analysis.

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