Tremendous numbers of the squid, Ommastrephes sloani pacificus STEESTRUPS, occurring during October to following March, have made the water around the Oki Islands one of the most important fishing grounds for them in the Japan Sea. With a view to elucidating mechanisms through which their shoals emerge into particular areas, the landing statistics by set nets for the 1950-'51 to 1958-'59 seasons (Table 1) have been examined in association with the data of tagging experiments and oceanographical surveys.
1) The data relevant to drift bottles recovered and drift buoys traced in 1955 indicate that all the surface currents around the southern mouth of the Oki Straits flow westward heading to Nakanoshima and Urago Bay (Fig. 4). Points of the bottle recovery coincided with those localities where tagged squids were recaptured. While some of those places have provided favorable sites for set nets particularly with a great concentration of the animal, the others are valuable grounds for angling boats aiming at the squid (Table 1, Figs. 1 and 3).
2) However, a check on Figs. 1 and 4 will reveal that some of the points to which drift bottles were often driven do not always produce successful catches even when they are located close to a favorable fishing ground. Because a water boundary or a counter circulation existing in the areas seems to separate those waters from the surface currents which bring the squid into the fishing grounds (Fig. 5).
3) From previous studies and commercial fishing practices it has been inferred that the squid diurnally repeats vertical migration, emerging from the bottom layer in the early evening and sinking down there at dawn. A postulation proposed here in regard to their horizontal migration is that shoals of the squid, after floating up to the surface, are transported from area to area along with the movement of water masses more possibly than by their own locomotion.
4) During autumn to winter thousands of the squid would often concentrate in Urago Bay. As the concentration occurs always at midnight in the bay shallower than 50m., they seem to take the rest in a deeper water outside the bay during the daytime.
5) Comparing the catches which accrued to Urago Bay and Nakanoshima during the 1955-'56 and 1956-'57 seasons, one may see that the fishing had success or failure alternatively at one of the places and in one of the seasons (Fig. 2). Those phenomena are possibly attributed to the surface current which, changing its direction from season to season, brings a greater number of squid to either one of the places.
6) Numbers of drift bottles released off the Oki Islands were recovered at points scattering over the coastal regions of Japan. According to Fig. 5, which combines these points with an annual average catch of squid and depth contours of these regions, an essential condition commonly applicable to the coastal regions presenting a favorable fishing ground for the squid is that a region should be provided with the 200m. depth contoure drawing close to the coast and with the surface current heading ashore.
7) Much remains to be solved in regard to detailed mechanisms inducing the squid to migrate vertically as well as horizontally. It may be a first approach to the questions to determine factors responsible for diurnal movements of the squid.

抄録全体を表示

As to the sex ratio of the Ayu crowding together at the spawning ground, it has been known that in the early period of the spawning season males predominate, while, on the contrary, towards the end of it females predominate. But no attempt has been made to investigate thoroughly the matter.
The present study was undertaken to study this problem. For this purpose, observations were made, on the one hand, on the seasonal changes of the sex ratio in connection with those of the maturity, population size and quantity of eggs spawned at two well-known spawning grounds of Sagami River in Kanagawa Prefecture. On the other hand, the spawing behaviour was observed in detail at artificial spawning beds which were prepared in experimental ponds.
The results obtained were as follows:
1) The proportion of females to the population exhibited marked seasonal changes. The number of males increased gradually from the early period of the spawning season to the height of it, where reaching its maximum. Thenceforth it gradually diminished (Fig. 1).
2) Parallelisms and also high correlations were found to exist between the proportion of male and population size or maturity (Fig. 2, 3). Furthermore the amount of eggs spawned showed a tendency to be largest when the proportion reached the maximum (Table 1).
3) Males, as the gonads matured, crowded together densely at the spawning beds. By this prespawning behavior silts laid on the gravel of the beds were removed. A few attendant females joined the male shoals, thus depositing their eggs. From these observations it would be assumed that the great proportion of males in the height of spawning was ascribed to such a spawning behaviour.
4) During the actual spawning process, much gravel of the beds were moved by fish, thus a circular hollow being formed (Table 3). A high correlation between the amount of the movement of gravel, which seemed to indicate the intensity of the spawning activity, and the quantity of eggs spawned was observed to exist (Fig. 7).

抄録全体を表示

The author has done to see stopping effects of electric fish screen in place of leading net.
Fish materials used were 10 Carassius auratus Goldfish of total length 5.0cm., and 10 Oryzias latipes Japanese Killifish of T. L. 2.5cm. as both live in fresh water, and 12 Sphaeroides niphobles Japanese common puffer T. L. 5-7.0cm. in sea-water.
Two electrodes are set in the upper and lower sides at the center of tank, and were closed alternate electric current of sine wave of 50 cycles regulating its voltage and amperage by transformers. (Fig. 1).
Frequencies of fish individuals pass through the center of tank were compared on cases closed and off the electric current.
The result is in Tables 1-4. which are taken efficiencies of passage and those significancy of stopping effects were judged. (Table 5).
In general, stopping effects of electric current in fresh water is about 50% on better condition, as if sufficiently available. The otherhand, the case of sea-water is about 20% and also, less availability, because it is required several hundreds times of amperage than the case of fresh water.

抄録全体を表示

The number of eel, Anguilla japonica in a culture pond (about 1 acre) was estimated by PETERSEN mark-and-recapture method, and the estimates which were obtained from the first set of data and that of the first and second sets of data, treated as a whole, were compared with the actual number of eel captured after the draining of the pond.
The results indicated that the estimates were fairly greater than the actual number of fish and the source of error was mainly attributable to misjudging some of the marked fish for those that were unmarked, which is caused by the rapid regeneration of the clipped fin in some of the marked fish.
The correction equation for p, marked ratio in samples, was derived as follows,
p=^p'-ε₁/_1-ε1-ε2
and
V( ?? )=^{(p'-ε₂)(1-p'-ε₁)}/_{n(1-ε1-ε2)²}
where p' is the apparant marked ratio in samples, p is the marked ratio in samples when there is no misjudgement, ε₁ is the rate of misjudging the marked as the unmarked, ε₂ is the rate of misjudging the unmarked as the marked, which is caused by deformity of the fin, and n is the size of samples.
In the present experiment, ε₂ was negleted and ε₁ was about 0.2. The recalculation, using the above equation, showed the new estimates were both in conformity to the actual mumber of fish.

抄録全体を表示

The method reported in the previous paper¹⁾ on pure myoglobin (Mb) solution was found to be also applicable to extracts prepared from tuna meat. The procedure is as follows: 10g. of the muscle finely ground in an ice-cold mortar are weighed into a glass-stoppered centrifugal tube and extracted for about 2 hours with 25ml. of ice-cold water with occasional stirring in an atmosphere of CO (cf. Table 1). After centrifugation, 15ml. of the supernatant are taken into another glass-stoppered centrifugal tube, to which some amount (usually 0.2 to 0.5ml.) of 1N NaOH solution are added for the purpose of removal of cloudiness, and the solution is left standing at least for one hour in a refrigerator. After centrifugation, 5 or 10ml. of the supernatant are diluted with 10ml. of ice-cold 0.2M phosphate buffer of pH 7.0 and divided into three portions. These portions are subsequently treated as described in the previous paper¹⁾ and percentage distribution of metmyoglobin (MMb) in the extract is calculated by the equation, a-d/a-b×100, as shown before¹⁾.
In calculating the content of Mb in tuna meat, some considerations should be paid which are not necessary in the case of pure Mb solution, especially on the impurities of extract which disturb the spectrophotometry and on the water content of meat, and the following equation is recommended:
y=(α-z)(S₁/10+S₂)10ƒM/E(mg.%)
where ƒ is dilution factor, S₁ water content (%) of the muscle, S₂ volume (ml.) of extractant used, M molecular weight of tuna Mb, E molar extinction coefficient of tuna carbonylmyoglobin (MbCO) at 568mμ, and z optical density at 568mμ by impurities. By the equation, z=bp-a/p-1, z may be obtainable, where p is a constant, the ratio of optical density at 568mμ of MbCO to MMb (4.31 in the case of Thunnus orientalis).
The reliability of the method was checked by the recovery tests which were very satisfactory (Table 2), and some experiments were cited as examples of application of this mothod (Tables 3 to 4 and Fig. 1).

抄録全体を表示

Mackerels were placed immediately after being angled in fish hold which contained regular ice and chlortetracycline (CTC)-containing sea water and kept for 6 to 7 days. Freshness and CTC-residue were estimated after landing. Further, a storage experiment at 3-7°C. was carried out in a store room of ice plant.
When mackerels were held in about 3 ppm CTC-sea water, the CTC residues in the muscle and the skin were found only 0.05ppm and 0.8ppm, respectively. When held in about 6ppm CTC-sea water, the residues in the muscle and the skin were found 0.09ppm and 1.25ppm, respectively. The distribution pattern of CTC in the muscle showed a sharp decrease in the residue within a 5-mm depth, and no CTC were found in the muscle deeper than 9mm.
When mackerels were stored at 3-7°C. after landing, the storage life of both the CTC-treated groups was 7 days as compared with 5 days for the control group. It is of interest that the formation of histamine in the muscle during the storage was greatly inhibited when the fish were dip-treated aboard ship.

抄録全体を表示

Although the coliform organisms have been employed as indicator for fecal pollution, it is said that these bacteria do not always represent pollution because they may persist in soil and water for long periods of time and occasionally multiply outside the animal body. In this regard, recently, enterococci have received considerable attention. At the beginning of the studies of enterococci as indices of pollution, in the present studies the author have investigated the comparative incidences of enterococci and coliform organisms in feces, soil and water. Although the fecal specimens of man and various animals contained both the organisms in great numbers, thirty-nine of fifty-five specimens contained greater numbers of coliforms than of enterococci. In all samples of soils and waters taken from the various environments coliform organisms were detected with a few exceptions, and throughout all the samples examined the numbers of these organisms were considerably greater than those of enterococci. The fact that coliform organisms were frequently found in uncontaminated soils and waters in mountain suggests that the organisms of this group may be of nonfecal origin or they may survive in such environment for long periods of time.

抄録全体を表示

Katsuwobushi is a dried product made from bonito meat by boiling, smoking, sun-drying and moulding processes and used for stock. The effects of these processes were investigated by analyzing the extractives of the each step product, especially free amino acids from the view point of its taste. The change of the contents of moisture, total-N, extractive-N and α-amino-N during the process is listed in Table 1 and that of free amino acids determined by the column chromatographic method using an ion exchange resing in Table 2.
The extracts of the raw material reveal a very high value of histidine which occupies about 80% of total free amino acids. The content of taurine, lysine and alanine is also found to be comparatively high, whereas aspartic acid, cystine, tryptophan and arginine are not detected. A portion of each amino acid is lost in the boiling process. During the smoking process, some amino acids increase slightly, others remain almost unchanged, but most of the amino acids decrease again in the course of moulding, perhaps in its earlier stage, judging from the changes of amino-N and histidine.
There have been some discrepancies among the reports on the change of free amino acids in the moulding process, but the present results do not support the opinion than the flavour of Katsuwobushi is improved by the increase of some amino acids due to the moulding.
Trimethylamine oxide disappears in the course of processing and is found to have nc connection with the flavour.

抄録全体を表示

The change of nucleotides during the manufacturing process of Katsuwobushi was examined on the same specimens described in the previous paper which dealt with free amino acids and other constituents in the extractives.
As shown in Table 1 and Fig. 1, inosinic acid is a predominant component occupying about 90% of the total acid soluble nucleotides, which contain only small amount of adenosine mono-, di-, and triposphates. Inosinic acid is lost to some extent during the manufacturing process, mainly in boiling and smoking processes, but it is fairly well retaind by the final product. Adenosine triphosphate, on the contrary, disappears in the process.
The results on various kinds of the commercial product are listed in Table 2, which shows that the inosinic acid content considerably varies with samples and has no definite relation with the place of production or the grade of quality. It is also found that the values are much higher than those reported so far. The histidine content estimated on six specimens ranges from 2.8 to 3.9% on dry basis and the molar ratio of histidine to inosinic acid from 9 to 25.

抄録全体を表示

The jelly strength of kamaboko was not affected so much by adding water to minced raw meat, as long as the amount of water did not exceed a limit, while when the amount of water exceeded this limit, the strength dropped down remarkably.
It was also found that the more water contained in kamaboko, the more the oil-water emulsion in kamaboko became stable, that is, the decreasing effect of oil mixed with kamaboko to the jelly strength was diminished.

抄録全体を表示

Intrinsic viscosity of a fibrous molecule is equal to reduced viscosity, η_sp/c, as both concentration, c and velocity gradient, ??, approach zero; thus [η]=(η_sp/c)_{c→0 ?? →0}
?? →0
A tilting viscometer, as reported in the previous paper¹⁾, affords a convenient method for measuring viscosities at varying velocity gradients, but the method requires some 90 minutes for working out a whole measurement. Thus in the present experiment, stability of carp actomyosin solutions are examined, intending to know whether a stock solution could be used in the viscosity measurement as in the case of rabbit actomyosin.
Stock solutions (0.3-0.5% solution of carp actomyosin in 0.6M KCl) were stored at 2-4°C and 20°C respectively, for 0, 1, 3, 4, 24hrs., and the solutions were diluted to a definite concentration (0.118%), relative viscosity being measured under varying velocity gradients. When stored at 2-4°C, the viscosity was found to have decreased after 1hr. and went on to decrease up to 3 hrs., approaching a limiting value (Table 1). When stored at 20°C, relative viscosity of carp actomyosin solution remained unchanged at least within 4 hrs., but after 24 hrs. a considerable decrease in viscosity was observed (Table 1).
The same results were obtained in the similar experiments with the solutions diluted prior to storage to desired concentrations.
Rabbit acotmyosin solution stored at 2°C for 24 hrs. showed no change in viscosity (Fig. 4).
Actomyosin prepared from carp muscle stored at 0°C for 24 hrs. gave the same viscosity as that extracted from the muscle immediately after death (Fig. 8).
Carp actomyosin prepared by 24hr. extraction gave a lower viscosity than that by 3min. extraction (Fig. 5).
Carp actomyosin solution showed a decrease in intrinsic viscosity from 4 to 2 after 24hr. storage (Fig. 1) which corresponds to reduction in the axial ratio from 70 to 50 in the case of a prolate. This considerable decrease in asymmetry of the solute molecule may possibly cause decrease in both structural viscosity and inter-molecular interaction. Actually there was observed decrease in slopes of the curves XZ and XY in Fig. 1, which represent the relations of (η_sp/c)_c→0- ?? and (η_sp/c) _{?? →0}-c respectively. The decrease in viscosity of the solution on storage, however, could not be attributable to dissociation of actomyosin into actin and myosin, since in salting-out curves the peak corresponding to actin failed to be observed with the both samples, the freshly prepared and stored solutions (Fig. 7).
The value of η_sp/c usually decreases with concentration, c, but abnormal cases were occasionally experienced with stored actomyosin solution. Thus η_sp/c took a minimum value at a certain concentration (Figs. 2 and 3). A series of experiments carried out monthly revealed that this abnormal behavior in viscosity was found always with carps in July and August, and sometimes with carps in June (Table 2).
An obvious difference in viscosity behavior was observed also among freshly prepared actomyosin solutions from rabbit and from carps of the two types (Fig. 10). Thus in rabbit, ln η_r/c is independent on concentration c, in normal carps increase in ln η_r/c is proportional to c, and in summer carps, the increase is greater than proportional to concentration.

抄録全体を表示