Studies on "amadai" (Gen. Branchiostegus) of Japan II.Spawning season of "aka-amadai"

Samples were collected at Sasebo Fish-marcket from June 1953 to February 1954. In June, ova-diameter in maximum (dx) was less than 0.20mm and gonadindex in average (GIm) was 0.85. From September to December, dx=0.68～0.72mm, and GIm=2.19 (Sept.), 2.18 (Oct.), 3.52 (Nov.-max.) and 2.02 (Dec.). In January and February, dx=0.14～0.18mm, and GIm=0.60～0.70.1953年6月から1954年2月に至る間に佐世保に陸揚げされた以西漁場産のアカアマダイ総計312尾について,月別に生殖腺指数及び各月の試料の内から体長約5mm間隔に8～14個体を抽出して卵数と卵径との関係を求め,又それ等抽出個体の最大卵径の分布状態をしらべた.6月には卵径が小さく熟卵も見られず,生殖腺指数が小さいが,9～12月には卵径の大きい熟卵が見られ,生殖腺指数は11月に山を示し,1～2月にはすべての状態が6月と同様になる.即ち以西漁場産のアカアマダイの産卵は9月にすでに始つて居り,11月に盛期に達し12月を以て終る

本邦産アマダイ属魚類に関する研究-1 : アカアマダイとキアマダイとの識別について

The author consulted the discriminating standards in the previous references, chiefly about external characters of the "amadai" of Japan. Color is variable and serration on the posterior margin of preopercle is rerative, therefore the species cannot be distinguishable by these characters. Firstly, a pearl-white spot in the form of an inverted triangle close to the postero-inferior angle of the eye is in "aka-amadai", while a stripe of the same color from the antero-inferior angle of the eye obliquely downwards and forewards in "kiamadai" (TANAKA, 1931).4) Secondarily, vivid yellow stripes are on the upper half of caudal fin in the former while some numbers of spots of similar color are noticeable on the lower half in the latter. These are very distinct and stable characters. Other characters which appear to occur are as follows: (1) Upper portion above the angle on the border-line between head-bones and preopercle is concave in the former, while nearly straight in the latter. (2) The caudal fin of the latter is darker in color than that of the former. (3) In the posterior margin of lower half of the caudal fin, concavity is more conspicuous in the latter than in the former. (4) Upper and lower lobes of the caudal fin are subequal in fength in the latter, while in the former the lower lobe is shorter than the upper one

ウミボタルCypridina hilgendorfii G.W.Muellerの生態に関する2,3の実験

The author made some experiments and observations concerning the ecology of "umihotaru". (1) Collecting apparatus. Using the plankton net of 20cm in diameter, the animals were collected in abundance. (2) Bait for collecting. Fish-wastes were used, hanging within the net opening. (3) Rate of luminescence of dried animals. 80-100% of the animals rapidly dried in the direct sunshine had luminous ability. The color was silvery white. (4) Rearing bait. Animals can be reared by giving some living fresh-water shrimps as a bait. (5) Variation of vertical occurrenc in the night. (a) In bottom layer there are 2 modes in the frequency curve (Fig. 1), i.e., 2-3 hours after sunset and before sunrise. (b) In intermediate layer (about 1.5m below the surface it appears to be reverse to (a), but indistinct. (c) In surface layer (about 20cm below the surface) it appears to be equal to (a), but the number is very small. (6) Lower limit of optimum salinity. Critical specific gravity of medium appears to be 11.00-12.00. (7) Reaction to light. Animals show negative phototaxis, while a closely allied species, i.e., C. noctiluca positive. (8) Chemical characters of luminous substance. (a) Substance which lost luminescent ability by oxidation, can be recovered by reducing by metalic magnesium. (b) Luminescence is very remarkable in the waters of pH above 7, decreases rapidly below 7 and no more below 4

The Hydrographic Conditions and the Fisheries Damages by the Red Water Occurred in Omura Bay in Summer 1965―III.The Oceanographic Conditions in the Offing Region of Omura Bay during the Term of the Red Water

There was observed a distinctive character in the oceanographic conditions of Omura Bay during the term of red water that the dissolved oxygen in the bottom water mass was remarkably lower in summer 1965 than in any past year. It is not clear how the occurrence of the red water was connected with the distribution of low dissolved oxygen, but the authors assume that the occurrence of low oxygen was caused, as follows. (1) The water mass lacking in dissolved oxygen occurred owing to the rising of water temperature, to the extension of thermocline by rainfall and to the stagnation of water mass by semiclosure, such being natural status of Omura Bay. (2) The degree of low dissolved oxygen was intensified by the decay and decomposition of the red water planktons which extraordinarily increased on the bottom layer

The Hydrographic Conditions and the Fisheries Damages by the Red Water Occurred in Omura Bay in Summer 1965―IV.Mass-Mortality of Fishes Resultant of the Red Water

The first red water appeared in the south-western coast of Omura Bay from middle July to early August, and the second one spread all over the southern part of the Bay from latter August to middle September 1965. Both bloomings were due to Gymnodinium sp. This paper mainly deals with the second one. This blooming was accompanied by the phenomenon that dissolved oxygen in the bottom water-mass dwindled into zero, and also by the mass-mortality of fishes―goby, blenny, globefish, common eel, octopus, dragonet, anchovy, gray mullet, conger eel, etc. Nevertheless the distribution of blooming was limited to the southern part and the water-mass without dissolved oxygen and the mass-mortality extended all over the bay. What has caused this mass-mortality ? From the status of the red water, the dissolved oxygen content in the bottom water-mass and the progress of decomposition above the ark shell, it was assumed that the mass-mortality of fishes and invertebrates was not caused by the red water, but primarily by the depletion of dissolved oxygen in the bottom water-mass all over the Bay

Studies on Attaching of the Barnacles in the Shallow waters.

Observations were carried out in Nagasaki Harbor from September 1960 to August 1960. Results obtained are as follows. 1) Attachment of the burnacles took place from the end of May to the middle of December when the water temperature was over 16℃, being most abundant in case of the temperature over 20℃ from the beginning of June to the middle of November, and pausing in case of the temperature under 15℃ from the end of December to the middle of March. 2) Attachment was most abundant in surface layer, and the deeper we went, the less we met. 3) For solid materials such as wood or bamboo, for example, the attachment at the beginning was more effective than for the artificial fibre such as polyetylene or "Kuremona", but some time after there was found no difference. This may probably be mainly due to watersuction and napping of the fibre. 4) Attachment to the dark-colored plate was more abundant than that to the light-colored, being abundant in black, red or blue, and scarce in purple or pink, and poorest in white, green or yellow.1960年9月から1961年8月までの1年間に亘って長崎港内の浅海帯におけるフジツボの着生試験を行ったが,その結果から次の事が考察された。① 長崎港浅海帯における着生状況は,15℃以上の3月下旬から12月中旬に着生が見られ,2C℃以上の6月上旬から11月中旬が繁殖期で,15℃以下の12月下旬から3月中旬までが休止期である。② 着生最大層は表面に近い所にあり,水深とともに減少した。③ 材料別による着生変化は,固形質の竹,木に比べ繊維質に着生量が少く,特にポリエチレン,クレモナ等の合成繊維に著しかつた。しかし繁殖期に入り,浸漬回数の増加とともに,これらの差が見られなかったのは,浅海特有の付着泥及浸漬回数増加による繊維のけば立ちと吸水力増加によるものと推定した。④ 彩色効果については,暗色系彩色に着生が多く,明るい白色系には少ないが,浅海帯では著しい傾向は見られなかった。一般に黒赤青に多く,紫桃がこれに次ぎ,黄緑白に少なかった

Relation between the oxygen consumption and the shell movement of the pearl oyster, Pteria martensii, in the sea water of low oxygen tension.

To obtain basic data useful for culture-technique as an adequate measure against the red water, an experiment was carried out by the authors in September 1965 on the oxygen consumption and shell-opening and -shutting, using 2-year-old pearl oysters. Effect of low oxygen tension was observed at a value less than 1.5～1.0cc/L, but the vital effect appeared at a value less than 0.2cc/L.酸素消費量と貝殻運動とから,アコヤガイと低圧酸素水との関係を検討した.水面を流動パラフィンでおおう方法には欠点もあるが,両者の関係を考える場合その結果を一応の目安とすることは出来るものと考える. 1) 酸素消費量は,環境水中の溶存酸素量が1.5～1.0cc/L程度までは,ほぼ一定の値を示して相関関係は認められず,それ以下になって急減する. 2) 貝殻運動の顕著な変化は,環境水中の溶存酸素量がそれぞれ1.5～1.0cc/L, 0.5cc/L, 0.2cc/L程度以下にそれぞれ低下した時にみられ,1.5～1.0cc/L程度で開閉の振幅が大きく頻度が急増し,0.5cc/L程度でやや振幅は小さくなり,さらに0.2cc/L程度以下になると長時間の閉殻がみられ,時間経過につれて順次大きく開殻する傾向がみられた. 3) 上述の結果から,低圧酸素の影響は1.5～1.0cc/L程度からみられるが,致命的な影響は0.2cc/L程度以下であらわれるものと推定し,真珠養殖における赤潮対策について論じた

Supplemental Report on the Relation between Pearl-Oysters (Pteria martensii) and the Current-Velocity of Environmental Waters : Effects of the Velocity of the Environmental Waters on the Motion of Shell-Opening and -Shutting and Shell-Regeneration

In the preceding paper, the authors reported the current velocity of 10～15cm/sec as the optimum for physiological activity of pearloysters. This value, however, is remarkably different from other author\u27s (OTA: unpublished, and SAWADA, and was obtained during November and December, the activity during which being probably low. The authors, therefore, carried out the supplemental experiments during May and June on the motion of shell-opening and -shutting, and during September and October on the regeneration of shell-edge respectively, both terms probably having optimum temperature of 20°～22℃ for pearl-oysters. Results obtained are as follows: 1. In the case of 3-and 4-aged shells, the shell-opening was wider at the velocity of 10±0.5～12±0.5cm/sec, and then, there was clearly seen diurnal periodicity. 2. In the case of 3-aged shells, the regeneration of shell-edge was the most active at the velocity of 12±0.5cm/sec. 3. At the velocity of more than 15cm/sec, there was seen an abnormality in diurnal periodicity of the motion of shell-opening and -shutting; and shell regeneration abruptly decreased. From the results mentioned above, we assume that the physiological activity of pearl-oysters, 3- and 4-aged, is the most vigorous at the current-velocity of 10～12cm/sec, and abruptly becomes low at the current-velocity of more than 15cm/sec.貝殻運動および貝殻形成力から,アコヤガイと環境水との関係を追試した. 1)3年貝と4年貝の各流速下における貝殻運動を比較した結果,10±0.5～12±0.5cm/secで開殻の幅が大きく,また明確な日週性が認められた. 2)3年貝を用い,その「ハサキ」再生重量から貝殻形成力を調べた結果では,12±0.5で最大値を示し,その前後で低下した. 3)15cm/sec以上では,貝殻運動の日週性に変調がみられ,貝殻形成力の急激な低下が認められた. 以上の結果から,10～12cm/sec程度の流速が,3～4年貝の場合には,その生活機能を活発にする流速で,15cm/sec以上で急激に機能は低下するものと推定した

Studies of the Oceanographic Characteristics of Haiki Channel and the Adjacent Waters, and of Effects of Closing of the Channel on Pearl Farms―I.Present Status of Plankton-Biota and Its Presumptive Changes

To elucidate presumptive changes in oceanographic characteristics of Haiki Channel and the adjacent waters by the closing of the Channel, the authors carried out the planktological investigations in September and November 1964, and January 1965. Results obtained and presumptions based thereon are as follows:― The present status of the plankton-biota in the above mentioned waters is "Sasebo type" (i.e. "Skeletonema type"). And, this status will not probably show remarkable changes, even if Haiki-Seto was closed, but there will take place an abnormal blooming of Skeletonema and the "Akashio" (red-tide). The authors assume that these phenomena will not probably threaten to kill pearl oysters, but the environmental conditions benefitable for Skeletonema will make drop value of pearl farms

Studies on the oceanographic and planktological characteristics of the Bay of Ômura : Preliminary II : Relation between the quantity of phytoplankton and the meteorological factors in the neighboring waters of the entrance of the Bay

Authors carried on daily observation to elucidate relation between the quantity of phytoplankton and the meteorogical factors, especially sun-shine and precipitation, in the neighboring waters of the entrance of the Bay of Ômura. During rainy seasons (June to July, & September), the quantity of phytoplankton increased when fine days continued after rainy days. It did\u27nt vary so remarkably when the meteorological conditions were stable after October.佐世保湾内の大村湾口附近に於いて日々観測を行い,日照時間及び降水量と植物性プランクトン量増減との関係を見た.6～7月の梅雨季には,降水が続いた後に晴天が続く時,必ずプランクトン量の著しい増加が見られ,9月の降水期にも此の傾向は認められる.10月以降気象条件が比較的安定して晴天が続き,水温条件は6月頃と同程度でも,プランクトン量の著しい増減は見られず,11～12月及び1月の冬期間も同様である.然し此の期間でも,多少とも降水を見た後にはプランクトン量がやや増加している傾向はうかがわれる.植物性プランクトンの増殖には或る限界以上の日射量は必要とするが,その限界以上でも,安定した環境条件の継続は活溌な増殖を促さず,その安定を破る様な条件が与えられて初めて増殖が著しく活性化される