The wrasse, Suezichthys gracilis, is a diurnal fish which buries itself in sand during the night-time. The present paper deals with the locomotor activity rhythms of S. gracilis, examined by using an actograph with infra-red photo-electric switches in a dark room. The fish were kept in eight experimental tanks (each 30l in capacity), with three different bottom conditions: sand (grain size about 1mm in diameter and 5 cm deep); 1 or 2 stones (about 10cm in diameter) without sand; and transparent acrylic pellets (2×2×3mm in size, 5cm deep). The light intensities were 550-700 lux just above the water surface, decreasing to 21.3% under the acrylic pellets at a water depth of 20cm. The water temperatures were kept at 22.0-25.0°C during the experiments for 7 to 14 days. In the aquarium with bottom sand, diel activity rhythms of S. gracilis were mostly synchronized to LD (LD12: 12; 06: 00-18: 00 light, 18: 00-06: 00 dark), free-running activity rhythms continued distinctly under LL (constant illumination), and locomotor activity was greatly suppressed, with disappearance of the activity rhythm, under DD (constant darkness). In the aquarium without sand, locomotor activity of S. gracilis could be summarized as follows. The fish moved throughout almost the entire period under LD, though more frequent movements were observed in light conditions than in dark ones. Under LL they showed continuous locomotor activity during the experiment, with no obvious periodicity. Under DD the activity of the species was somewhat suppressed, but irregular movement or indistinct periodicity was observed. In the aquarium with transparent acrylic pellets, locomotor activity under LD and DD, respectively, bore a close resemblance to activity patterns under the same light conditions with sand, whilst activity under LL was identical to that under LL without sand. Accordingly, it seems that maintenance of normal activity rhythms in the wrasse was due not only to the darkness, but also to the presence of bottom sand. It therefore seems that the biological clock in S. gracilis is not related to locomotor activity, but to burying behavior.

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A female basking shark (5710 mm TL), Cetorhinus maximus (Gunnerus, 1765) (Lamniformes: Cetorhinidae), was collected from a set net off Chojagasaki, Sagami Bay, on 29th March 2016. This occurrence represents the fourth record and largest specimen of the species collected from the bay. The frequency of occurrence in Japanese waters appears to be decreasing in the 21st century.

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The locomotor activity rhythms were examined by using an actograph with infra-red photo-electric switches for two species of wrasses, (Halichoeres tenuispinnis and Pteragogus flagellifera) under various light conditions. In H. tenuispinnis, the locomotor activity of almost all fish under light-dark cycle regimen (LD12: 12; 06: 00-18: 00 light, 18: 00-06: 00 dark) commenced somewhat earlier than the beginning of light period and continued till somewhat earlier than the beginning of the dark period. This species clearly showed freerunning activity rhythms under both constant illumination (LL) and constant darkness (DD). Therefore, H. tenuispinnis appeared to have a circadian rhythm. The length of the circadian period ranged from 23hr. 30min. to 23hr. 44min. under LL, and was from 23 hr. 39min. to 24hr. 18min. under DD. On the other hand, the locomotor activity of P. flagellifera occurred mostly in the light period under LD 12: 12. The activity of this species continued through LL, but was greatly suppressed in DD, so that none of the fish had any activity rhythm in both constant conditions. It was known from field observations that H. tenuispinnis burrowed and lay in sandy bottoms, while P. flagellifera hid and rested in bases of seagrasses and shallow crevices of rocks during the night. In the present two wrasses, it seemed that the above-mentioned difference of noctural behaviorwas closely related to the intensity of the endogenous factor in the activity rhythm.

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Fouling by the green mussel, Perna viridis, on the oyster beds in Aioi City and along the coast of northern Harima-nada, Hyogo Prefecture was investigated. In this study the first observed mass of green mussels adhering to cultured oysters was in August, 1998 with a shell length about 5 mm. By the end of November the largest one grew to 47 mm. Growth slowed down with the seasonal fall in water temperature, and mortality increased. Detachment from the substrates was observed in the end of January, 1999. At water temperatures below 10°C, mass mortalities of the green mussel were observed.

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Ichthyofauna of Sagami Bay has been researched bay landing fishes of Misaki Fish Market, and 567 species has been recorded since 1986. In the paper, seven species are additionally recorded.

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Locomotor activity rhythms in the hagfish Paramyxine atami were studied using the same procedures as were employed in a prior study of Eptatretus burgeri. Swimming activity under 12L: 12D (7:00-19:00 light, 19:00-7:00 dark) appeared at the beginning of the dark period and at the onset of the light period. In E. burgeri such activity occurred regularly in the first 2/3 of the dark period. P. atami exhibited a labile free-running rhythm of swimming under continuous darkness. After reversal of the light-dark cycle (7:00-19:00 dark, 19:00-7:00 light), the aver-age time necessary to shift to the new dark period was 3.7 days, in contrast to 7.7 days which E. burgeri required. The differences in the activity patterns of the two species may be ascribed to differences in their natural habitats: P. atami resides in deep waters, and cannot be so much in-fluenced by sunlight as E. burgeri.
It may be speculated that P. atami has a relatively “delicate” circadian oscillator, and the external light used in these experiments has a relatively strong effect in regulating locomotor ac-tivity, with the result that activity shifts in a short time after reversal of the light-dark cycle, and temporary activity is evoked at the onset of the light period.

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マンボウの産卵期を調べるために, 1981年から2006年までの間に関東沿岸で捕獲された183尾のマンボウを用い, 生殖腺指数 (GI) の変化を調べた。同様に, 9個体の天然雌 (TL185-272cm) と4個体の天然雄 (TL168-190cm) の生殖腺を組織学的に調べ, GIの変化とあわせ産卵期を推定した。天然魚のGIの最大値は雌雄ともに8月に認められ, 組織学的な観察から卵母細胞は4つの成熟段階に分類された。卵巣のGIおよび成熟段階の季節的変動から産卵期は8月から10月の間に認められるものと考えられた。また, 卵巣の成熟様式が非同期発達型であったことから, マンボウは多回産卵魚であると考えられた。

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The hagfish Paramyxine atami shows a clear nocturnal rhythmicity of locomotor ac-tivity. Entrainability of locomotor activity rhythms in the hagfish were tested under reversed light-dark cycles with light intensities of less than 1.0 lx.
The shifting of activity to the newly established dark period became defective and unstable with decreased light intensity in the light period. Entrainability to the LD cycle was still observed at the intensity of 2.53× 10^-3 lx. These findings for P. atami are com-pared to a closely related species E. burgeri. The functional threshold of photo-receptors in P. atami seems to be lower than that in E. burgeri. Likewise, there is a difference in the vertical range of their habitats: E. burgeri and P. atami inhabit, respectively, depths of 10-100m and 50-500m. It is suggested that the activity rhythms in P. atami can be regulated by weaker light intensities than those in E. burgeri and that this relates to the difference in their natural habitats.

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Locomotor activity rhythms in the hagfish Eptatretus burgeri were recorded by use of an electronic photo-switch system. The activity in the hagfish occurred in the dark period of a 12L:12D cycle even if the cycle was reversed.
Entrainability of the activity rhythm to the reversed LD cycle was also measured under dim light intensities of the light period. Defective phase-formations were produced when the light intensity fell as low as 5.96×10^-3lx. The activity phase was no longer entrained by the LD cycle in the intensity of 2.53×10^-3lx. It is estimated that the light intensities used in the experiments occur at depths of 100-150m of Sagami Bay, which the hagfish inhabits in summer. Thus, an external LD cycle, even with such dim light, might regulate locomotor activity in the hagfish under natural conditions.

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Light pulses of 15min to 6h were given to the hagfish Paramyxine atami, individuals displaying a free-running rhythm in locomotor activity under continuous darkness. The fish sensitively responded to the pulses; the active phase was promptly delayed or advanced when pulses were respectively given at the beginning or at the end of the duration of locomotor activity (α). The responses to light pulses in P. atami were characterized both by an initial phase-shift and by the changing period length (τ) in the ensuing active phase. In contrast, a closely related hagfish species Eptatretus burgeri responded to the light pulses by taking another stable course of the ensuing active phase with relatively constant τ
These results suggest that the sensitivity to light pulses in P. atami is higher than that in E. burgeri.

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Occurrences of tiger shark, Galeocerdo cuvier (Péron et Lesueur, 1822) (Carcharhiniformes: Carcharhinidae) in Sagami Bay are reviewed. It is clear from several records that the species occasionally enters to the bay. However, the record based on a specimen which guarantees the identification and various biological informations is known to only an example in this report. It is necessary to construct a network among citizens, fishermenʼs cooperatives, fisheries experimental stations, aquariums, museums, etc. for collecting of occurrence records of large elasmobranchs.

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Occurrences of basking shark, Cetorhinus maximus (Gunnerus, 1765) (Lamniformes: Cetorhinidae) in Sagami Bay were reviewed. There are three certain records of this species in the bay: an individual fished off Enoshima in March 21, 1961, a female of about 4 m in total length fished off Sajima in June 8, 2005, and a male of 4.74 m in total length fished off Chojagasaki in April 26, 2009. These fishes were captured with a set-net, and immature in all cases. When we analyzed sea conditions of April 24 to 27, it was suggested that occurrence of Chojagasaki's specimen is no relation to the Oyashio Current. We presumed that this species strayed accidentally into the bay because of extremely low frequency of occurrence.

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Under controlled laboratory conditions, the locomotor activity rhythms of four species of wrasses (Suezichthys gracilis, Thalassoma cupido, Labroides dimidiatus and Cirrhilabrus temminckii) were individually examined using an actograph with infrared photo-electric switches in a dark room at temper-atures of 21.3-24.3°C, for 7 to 14 days. The locomotor activity of S. gracilis occurred mostly during the light period under a light-dark cycle regimen (LD 12: 12; 06: 00-18: 00 light, 18: 00-06: 00 dark). The locomotor activity commenced at the beginning of the light period and continued until a little before the beginning of dark period. The diel activity rhythm of this species synchronizes with LD. Under constant illumination (LL) this species shows distinct free-running activity rhythms varying in length from 23 hrs. 39min. to 23 hrs. 47min. Therefore, S. gracilis appears to have a circadian rhythm under LL. However, in constant darkness (DD), the activity of this species was greatly suppressed. All the fish showed no activity rhythms in DD conditions. After DD, the fish showed the diel activity rhythm with the resumption of LD, but this activity began shortly after the beginning of light period. The fish required several days to synchronize with the activity in the light period. Therefore, S. gracilis appeared to continue the circadian rhythm under DD. In T. cupido, the locomotor activity commenced somewhat earlier than the beginning of the light period and continued until the beginning of the dark period under LD. The diel activity rhythm of this species synchronizes with LD. Under LL, four of the five specimens of this species tested showed free-running activity rhythms for the first 5 days or longer varying in length from 22 hrs. 54min. to 23 hrs. 39 min. Although the activity of this species was suppressed under DD, two of five fish showed free-running activity rhythms throughout the experimental period. The lengths of such free-running periods were from 23 hrs. 38min. to 23 hrs. 50min. under DD. Therefore, it was ascertained that T. cupido has a circadian rhythm. In L. dimidiatus, the locomotor activity rhythm under LD resembled that observed in T. cupido. The diel activity rhythm of this species synchronizes with LD. Under LL, four of seven of this species showed free-running activity rhythms throughout the experimental period. The lengths of such free-running periods were from 23 hrs. 07min. to 25 hrs. 48min. Although the activity of this species was suppressed under DD, three of five fish showed free-running activity rhythms throughout the experimental period. The lengths of such free-running periods were from 23 hrs. 36min. to 23 hrs. 41min. under DD. Therefore, it was ascertained that L. dimidiatus has a circadian rhythm. Almost all locomotor activity of C temminckii occurred during the light period under LD. The diel activity rhythm of this species coincides with LD. Under LL, two of four of this species showed free-running activity rhythms throughout the experimental period. The lengths of such free-running periods were from 23 hrs. 32min. to 23 hrs. 45min. Although the activity of this species was suppressed under DD, one of the four fish showed free-running activity rhythms throughout the experimental period. The length of the free-running period was 23 hrs. 21min. under DD. Therefore, C temminckii appeared to have a circadian rhythm. According to field observations, S. gracilis burrows and lies in the sandy bottom while T. cupido, L. dimidiatus, and C. temminckii hide and rest in spaces among piles of boulders or in crevices of rocks during the night. It seems that the differences in nocturnal behavior among the four species of wrasses mentioned above are closely related to the intensity of endogenous factors in their locomotor activity rhythms.

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従来から, 地震が起こる前に発光や動物の異常行動など, 地震の前兆らしき現象が数多く報告されている.これらの「宏観異常」と呼ばれる現象と地震との因果関係は未だ科学的には明らかになっておらず, むしろその信憑性の不確さから非科学的とされる傾向にあった.しかし, もしこれらの現象が真に地震に関連して発生しているのであれば, 予知への利用という観点からは捨てがたい情報である.
そこで著者らはこの宏観異常情報の特性を明らかにしたうえで, インターネットやデータベースなどのコンピュータ技術を活用してこれらの情報を収集・蓄積・解析する方法を検討し, インターネット上でWebサーバとデータベースを連動させたシステムを開発して試験運用を行った.またこれらの成果をもとに現行システムの問題点を考察し, より客観的な情報を抽出するための改善策など, 本格的運用に向けての検討を加えた.

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アカメフグTakifugu chrysops (Hilgendorf) は桃黄色ないし橙褐色の地色に黒褐色の棒状または円点状の斑点が散在し, 目は赤橙色を呈する小型のフグで, 房総半島から土佐湾に至る本州太平洋岸に分布し (Abe, 1949;蒲原, 1950), 沿岸の底刺網, 小型定置網で漁獲されるが漁獲尾数は少く, 初期生活史については未だ報告がない.筆者らは1984年本種の人工授精を行い, ふ化仔魚を約5ヵ月間飼育したので, 本種の産卵期, 卵発生, 仔稚魚の形態, 成長について報告する.

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Specimens of Canthigaster rivulata (Temminck et Schlegel) were collected from Kominato and Hayama, central Japan, from May, 1985 to October, 1986. On the basis of the gonadosomatic index, gonadal histology and results of artificial fertilization of these specimens, the spawning season is considered to extend from late June to mid-September. The specimens exhibited the following dimorphic differences associated with sex: 1) The male is larger than the female. 2) Ventral side of the body is brownish orange in the male with vermiculated or reticulated patterns of bright violet, while it is white in the female. 3) The male has a well-developed skin fold along the mid-dorsal and mid-ventral lines, which is greatly elevated during courtship; whereas the female's skin folds are not or slightly developed and conspicuous only during courtship.In an aquarium with the water temperatures of 22 to 26°C, a pair of fish spawned every four days late in the morning for three consecutive months. Courtship and spawning occurred in a pair. The male swam in front of the female, and elevated the skin folds both dorsally and ventrally, fully spreading the unpaired fins, with the ventral side of the body flashing bright blue and the dorsal side turning dark. Both fish swam in a circular fashion, elevating the skin folds. The male followed the female nudging her abdomen with his snout. Both fish turned upward, and released gametes. The eggs are spherical, 0.53-0.73mm in diameter, demersal, adhesive, transparent, and pale yellowish orange in color, and contain a cross-shaped or asteroid cluster of oil globules. The egg membrane was thick and consisted of about 14 concentric layers. The incubation period ranged from 73.5 hours at 28.2-28.5°C to 145.0 hours at 22.1-22.4°C. The newly hatched larvae were 1.38-1.98mm in total length (TL) with 8+11-13=19-21 myomeres. The yolk was absorbed when the larvae attained 1.49-2.22mm TL, three days after hatching. The larvae were fed on oyster larvae, blue mussel larvae, sea-urchin larvae and rotifers, but all of them died in 16 days. During the embryonic and early larval stages, the only pigment cells that appeared on the body were the black chromatophores.

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