The oceanographic investigations and fishing by one-boat medium trawling were carried out at about one hundred and fifty stations on the continental shelf of the eastern Bering Sea during the period from April to June, 1960.
In this region, two distinct fronts of water are encountered: that of the relatively warm water above 3.5°C which creeps into the region along the sea bottom from the southwestern offshore region, and that of the cold water below 0°C which has been severely cooled beneath the ice of the sea during the preceeding winter over the northern portion of this region.
During the spring from April to May, in the vicinity of the front of the relatively warm water a tremendous number of fish abound, especially yellow-fin sole, Limanda aspera which is the most dominant species in this region. In June, when the bottom temperature rises a little gradating the front of the cold water, the shoals of yellow-fin sole move northeastward into the cold water region detouring around the severely cold water below 0°C. In this season the shoals of yellow-fin sole disperse widely and the catches by fishing boat decrease rapidly. After this, they move to the west toward the deeper cold region during the rise of bottom temperature in the shallower coastal region.
About that time, a large gradient of temperature begins to form approximately along the 50-meter contour of the bottom. This is due to the fact that the water shallower than 50 meters is well mixed from surface to bottom through the connection of the upper layer mixed by wind action and the lower layer disturbed by bottom friction increasing the bottom temperature, while the water deeper than that forms s thermocline between the upper and lower layers preventing the heat from being transported downward.
The yellow-fin soles, at this time, again close up in shoals along this belt-like region of the large gradient of temperature, perhaps being retarded there, on the way of their westward migration.
To examine the process of the change of the bottom temperature, the amount of heat received at the surface was calculated at two stations where the observations were made twice at an interval of about twelve days. The heat amount received at the surface approximately agrees with the increase of the heat content at the stations, showing that the rise of the bottom temperature is due to the surface heating and vertical conduction. In addition, the values of vertical eddy conductivity in the thermocline were calculated together with those at several stations where the change of the bottom temperature greatly influences the movement of the shoals of yellow-fin sole as mentioned above.

抄録全体を表示

The author studied the seasonal variations in water temperature at various depths and sub-regions in the area of Caroline and Marshall Islands. The seasonal variation in the water temperature at surface and 50 meters in depth was found to be different from those of 150, 200 and 300 meters in depth. In the earlier period of the year the water temperatures at surface and 50 meters in depth were lower than those of the latter period but the water temperatures at the other deeper layers in the earlier period were higher than those of the latter period of the year.

抄録全体を表示

In the present paper, the author analysed the relations between the seasonal variations in the depth of several water temperature layers and the swimming depth of yellowfin tuna, big-eyed tuna and blue marlin. The results obtained are as follows:
1) The swimming depth of yellowfin tuna and big-eyed tuna seemed to be related to the seasonal variation of the depth of 28°C water layer, and blue marlin 27.0°C and 27.5°C layers.
2) From the above results, the swimming depth was thought to be from 50 to 70 meters in depth for yellowfin tuna and big-eyed tuna and from 60 to 90 meters for blue marlin.

抄録全体を表示

The present study has been done to make clear the movement of food materials with the lapse of time in the alimentary system and the selection of the particle size at the external organs relating to feeding and the digestive organs. Yearling oysters, 4.5-5.5cm. in shell hight, were placed in sea water with suspension of powdered charcoal in a culture vessel, where water temperature was kept at 21-22°C. Specimens removed at intervals of thirty minutes from the vessel were fixed in 20% formalin, sectioned according to the routine paraffin method and stained with eosin. Microphotographs were taken of preparation thus prepared and the size of charcoal particles existed in various parts of the alimentary system were determind with the photographs.
1. Changes of the particles in various regions of alimentary system with the lapse of time observed were shown in Fig. 1-8.
(a) Most of the fine particles carried to the stomach were coated by a mucus substance presumed to be originated from the crystalline style, forming a mucus grain, 1 or 2 hours after the end of feeding. The size of mucus grains measured 5-10μ in diameter (Fig. 2).
(b) The mucus grains were transported into the tubule of digestive diverticula after 2 to 4 hours, most abundantly after 3 to 3.5 hours. The size of the particles phagocyted by the tubule cells was under 5μ in diameter (Fig. 3, 4).
(c) Excretory spheres produced by the fragmentation of the tubule cells, enclosing the charcoal particles were found in the duct of digestive diverticula from 3 hours after feeding, the eize of the excretory spheres measuring 10-15μ (Fig. 5).
(d) The quantity of the particles contained in the excrement reached the maximum 2.5 to 3.5 hours after feeding. The particles were greater in size till 3 hours after feeding, thereafter smaller particles gradually increased with time (Fig. 7, 8).
2. The size of the particles distributed in various parts of the alimentary system was measured with the following results.
(a) A maximum size of the charcoal particles used measured 52.5μ in length and 20μ in width, and the largest of those taken into the oesophagus were 30μ and 17.5μ respectively. There seems to be a tendency that the smaller the size of particle of the material, the higher the rate of passage into the stomach from the surrounding water (Table 1, 2 and Fig. 9).
(b) A maximum size of the particles transported into the tubules of digestive diverticula from the stomach measured 17.5μ in length and 10μ in width. There is also a tendency that the smaller the size of the particles, the higher the rate of transport into the tubule from the stomach. Those particles under 2.5μ in length and those under the same size in width account for about 67% and about 75% of the particles transported in the tubules, respectively (Table 2 and Fig. 9).
(c) The volume of particle inhaled was calculated on a theoretical cube (πR⁸/6) of length or width of particule measured, thus deriving two kinds of calculations. The observation showed a tendency that the greater the size of the particle, the greater the quantity of charcoal ingested within a limit of size selection of the animal. A similar tendency, however, was not recognized with those under 5μ in both length and width in the tubule, which size is deemed to be an upper limit of the particles phagocyted in the tubule cell of digestive diverticula (Fig. 10).

抄録全体を表示

To study on the spawning condition of the northward migrating saury in adjacent waters to Oki Islands, 25 times horizontal surface hauls with 1.3m, larval net were carried out during the period of main spawning season of the fish from May to June in 1962. And about 5kg. masses of floating seaweeds consisting of those caught with the larval net and those entangled in drift nets from 18 stations, were examined to calculate the number of saury eggs deposited on the weeds.
1) Total number of eggs and larvae collected in the periods of the investigation amounted to 1, 520, 000 and 14, 800 individuals respectively. The number of eggs per lgr. floating seaweeds, to which the eggs attached, varied from 10 to 1, 140, and the average being 388. The number of larvae per haul of larval net was 291.
2) As to the relation between the oceanographical structure and the distributions of eggs and larvae of saury, the following results were obtained.
The eggs of the saury were distributed abundantly along the boundary zone between the 2nd branch of the Warm Tsushima Current and the ‘Offshore Low Temperature Region’, (SHIMOMURA and MIYATA, 1952), but the larvae were distributed abundantly in the coastal water region (the 1st branch of the Current).

抄録全体を表示

Diseased eels collected from eel-culturing ponds where the so-called fungus disease was prevailing presented mostly external and internal symptoms characteristic of Aeromonas infection. While about one fifth of the diseased eels examined showed no signs of fungus infection.
Aerononas liquefaciens was regularly isolated from the skin lesions and/or the viscera of diseased fish.
Eels inoculated intramuscularly with this bacterium became easily infected with Saprolegnia Parasitica and an appreciable parallelism was found between severity of “Aeromonas disease” and that of fungus infection.
The conclusion, therefore, is that A. liquefaciens is the primary causative agent of the so-called fungus disease of eels.

抄録全体を表示

In the present investigation an attempt has been made to provide some feature of L-ascorbic acid (AsA) utilization in the intact carps. The results obtained are as follows.
1) The body pool size and the turnover rate of AsA were obtained by introducing labeled ¹⁴C-AsA directly into the body. The subsequent fall in the specific activity of visceral AsA with time provided the data from which the turnover measurements were calculated. The results indicate that the body pool of AsA in carps averaged 16.1mg per 100g of body weight, the turnover time averaged 5.5 days, and the turnover rate averaged 2.9mg per 100g of body weight per day.
2) AsA was administered to carps, and the metabolic products excreted was measured on successive day. The results indicate that the excretion of oxalic acid increased, the excretion of fumaric acid, succinic acid and citric acid did not change, and no AsA appeared.

抄録全体を表示

In 1962, some deformities (scoliosis or lordosis) of rainbow trout fed mainly with artificial dried diet were found in many fish ponds.
The cause of the deformity of rainbow trout has been studied from a nutritional viewpoint. From the results shown in Tables 1 to 5, it was revealed that the deformity was developed by the deficiency of, L-ascorbic acid in the diet used. The symptoms may essentially be included in the category of scurvy of higher animals. The deformity observed can tentatively be classified into 3 types a, b and c according to the appearance of the symptoms which varied with the size of fish (Figs.1 to 3).
Halver et al.¹⁾ have reported the development of scoliosis in rainbow trout fed the diet deficient in tryptophan. It is reported¹⁶⁾, however, that the requirements of ascorbic acid of guinea pig considerably increase under the tryptophan deficient condition. Thus it is considered that the scoliosis reported by Halver et al. may have arised from an ascorbic acid deficiency.
The present studies also revealed that p-aminobenzoic acid was not essential dietary factor for rainbow trout as previously reported by Halver et al.²⁾

抄録全体を表示

In starch gel electrophoresis of carp hemoglobin the patterns generally appeared obscurely, which was assumed to be caused by concomitant existence of metform, more or less, in the sample solutions of oxyhemoglobin. Therefore it was thought that the uniformity in the derivative form of hemoglobin was necessary for the experiment. For this purpose metform and also oxyform are unsuitable, the former trailing markedly and the latter being liable to autoxidation. As compared with those derivative forms, cyanmetform was found to be much more favorable, hemoglobin patterns in this form appearing clearly.

抄録全体を表示

Starch gel electrophoresis of hemoglobins of many kinds of fishes and whales was carried out using the sample solution of cyanmethemoglobin. As to the hemoglobins of fishes, for example, chum salmon and eel, that had been thought to be composed of two components by analysis of T_ISELIUS electrophoresis, they were clarified to have two groups, one group moving to anode and the other group to cathode, each of which separated into more than two components by starch gel electrophoresis. Remarkable differences were also observed among three species of tuna which are classified in one genus, Thunnus. As far as studied here, there was no fish whose hemoglobin consists of a single component. It might be said that fish has more hemoglobin components, compared with higher vertebrata.

抄録全体を表示

Many microorganisms were isolated from sea water samples which were taken from various depths of about 1000 meters on the cruises of the “Oshoro Maru” and “Hokusei Maru” in the North Pacific in 1958 and 1960.
For isolation of microorganisms the medium adopted was ZoBELL 2216-E, and five strains among the many isolates were agar softening bacteria.
The classification of these agar softeners was made according to the Bergey's Manual of Determinative Bacteriology (1957) and method by SHEWAN. In this paper, a taxonomic investigation for these agar softeners was made at the generic and species level. Genera, Pseudomonas, Vibrio or Alginomonas, were the most suitable for these agar softeners from a point of view based on their morphological and physiological characteristics, and these agar softening bacteria did not agree with the species described in Bergey's Manual (1957) and by other workers.

抄録全体を表示