12 research outputs found
Studies on the marine cladocerans-I. : A biological note on Penilia
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æµ·ååŸçã«é¢ãã2å®ç¹ã«ãããŠïŒ 1966-1967幎ã®1幎éæµ·ç£æè§é¡ã®èª¿æ»ãè¡ãªã£ã.åºçŸãã5çš®ã®ãã¡ãŠã¹ã«ã¯ããžã³ã³ïŒPenilia schmackeri RICHARDïŒã«ã€ããŠè¥å¹²ã®èŠ³å¯ãè¡ãªãïŒæ¬¡ã®ãããªçµæãåŸã.
1) Penilia ã®åºçŸã¯6æäžå¥ã«ã¯ããŸãïŒãã®åŸæ¥æ¿ã«å¢å ããŠ7æåæ¬ã«æé«25ïŒ000fåäœ/m3 ã®å¯åºŠã«éãã.以åŸæ¥éã«æžå°ããŠãã9æã«ã¯ã¿ãããªããªã£ã(Table 2).
2) äœé·ã®ååžã¯0.38-0.93 mm ã«ããããïŒå€§å¥ããŠå€§å°ã®2矀ã«ãããïŒå€§å矀ã¯äž»ãšããŠæ±åµåŽäœçŸ€ããæã(Text-fig. 3).
3) Penilia ã®äœé·ã¯åºçŸåæããé 次å
ããªããå°ãããªãããã§ãããïŒé1å°Ÿãããã®æ±åµæ°ã¯åºçŸåæã®å¹³å7.5åããææ¥ã®çµéãšãšãã«ããããŠé¡èã«æžå°ããåŸåãèªãããïŒ 8ææ«ã«ã¯å¹³å2.0åãšãªã£ã(Text-fig. 4).
4) ããããå€åµãæããåäœã®å ããå²åã¯ïŒåºçŸåæã«ãã§ã«25ïŒ
ã瀺ãïŒ7æåæ¬ã«æé«69%ã«éãïŒä»¥åŸæ¬¡ç¬¬ã«äœäžããŠ40%ååŸã«è³ããïŒéäž6ææ«é ããïŒããªãã¡çŸ€éå¯åºŠãæé«ã«éããçŽåã«éåäœãšãšãã«èä¹
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åã«æé«ã«éã10%ã«åãã (Table 3ïŒText-figg.6).The population of the marine cladocerans was followed up at the two stations in Bingo-Nada, the Inland Sea of Japan, during the period from November 1966 through October 1967.
By the observations made on Penilia schmackeri RICHARD, one of the five species of cladocerans occurred, the following results were obtained:
1) Penilia first appeared in the middle of June; then a sharp increase in number was observed, reaching the maximum value of about 25,000 individuals per cubic meter in early July. After that, the numbers decreased rapidly to zero towards September.
2) Standard length varied within the range of 0.38 to 0.93 mm. There was a general tendency that groups of two sizes seemed to be seen. The larger group was mainly composed of egg-bearing females.
3) The standard length of females with eggs seemed to become gradually smaller from the time of its appearance to the later period, while the fertility as expressed in quantity of eggs or embryos per brood was highest (7.5) at first, followed by a drastic decrease thereafter.
4) Females with summer eggs took up about 25% of the population in the middle of June just after its first appearance. They attained their maximum (69%) in early July, then gradually decreased in number to about 40%. Sexual individuals, namely females bearing a resting egg and males, occurred already in late June, shortly before the highest population density, and continued to be seen until the end of August when Penilia was going to disappear
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ãã¢ãªã¢ã±ããã¯ãã ã· (Corphium acherusicum COSTA) ã¯ãšã³ãšãäºç® (Gammaridea) ïŒ ããã¯ãã ã·ç§(Corophiidae)ã«å±ãã端èé¡ã§ãã£ãŠïŒ å
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3) ç£åµã¯åšå¹Žã²ãç¶ããŠã¿ããã. ãããç£åµæŽ»åã¯3æ-7æäžæ¬ã«æã掻çºã§10æ-11æãããã«æ¬¡ãé«ãïŒçå€ããã³å³å¯ææã«ã¯ïŒããªãäœããªãåŸåãã¿ããã.
4) æ±åµéã®äœé·(LïŒmm) ãšæ±åµæ°(N) ãšã®é¢ä¿ã¯N= 0.28L2.98ãªãææ°åŒã§ç€ºããã.
5) æ§æ¯ã¯å¹ŽéãéããŠå¹³åãããšé1. 6:é1ã®å²åã§ããïŒéã®æ¹ãåžžã«ããå€ã.
6) 管棲端èé¡ã®çæ
çæ矩ã«ã€ããŠïŒäž»ãšããŠæ±æçç©åã³é£Œæåç©ãšããŠã®éèŠæ§ãäžå¿ã«ïŒè¿°ã¹ã.Observations were made on the population of a marine tubicolous amphipod, Corophium acherusicum COSTA, which was found in greatest abundance in Fukuyama Harbor, Inland Sea of Japan. The results obtained are summarized as follows :
1) Abundance in population density, as expressed in terms of the number of individuals per unit weight of dried mud-tubes of C. acherusicum, fluctuates seasonally, showing a single prominent peak in June.
2) There is a remarkable seasonal variation in size of both male and female, being larger in colder season than in summer season. This fact suggests the presence of large-sized over-wintering generations and small-sized summer generations. In general, the females are larger in size than the males.
3) Breeding continues throughout the year. But, there is an indication that the breeding seems most active in March-mid-July and next, October- November. Both in the coldest and the warmest seasons breeding activity may be suppressed.
4) The relationship between the number of eggs incubated in brood pouch (N) and the standard length of mother animal (L, mm) can be expressed as N = 0.28L2. 98.
5) The females are commoner than the males. The average sex-ratio is 1.6 (females) : 1 (male).
6) Importance of the amphipod as the member of fouling community and the prey for some littoral young fishes is described
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iii) ããããŠçšã«åºçŸãããã®:ã¯ãã¢ããŽïŒãµã³ãïŒã®ã³ã«ã¬ãç.1) Almost year-round investigation was carried out on the catch of masu-ami, a kind of pound net, in Kasaoka Bay located in the central part of Seto Inland Sea.
2) A list of species found in the catch was presented, in which 83 species of fishes belonging to 48 families were contained, with 11 species of cephalopods, 11 species of crustaceans and I species of Xiphosura.
3) Characteristics in the composition of the catch of masu-ami were shown. Among the animals caught fishes dominated in number and weight, comprising 82% and 71% of the total catch, respectively. The catch per haul fluctuated with seasons, being greater in summer and smaller in winter.
4) Growth as deduced from length-weight measurements and weight-length relationships were described on several fishes captured abundantly during the present investigation.
5) On the basis of seasonal occurrence and abundance, the fishes of Kasaoka Bay can be grouped into the following three ecological categories.
i. Year-round "residents" : Apogon lineatus, Leiognathus nuchalis, Rudarius ercodes, Harengu/a zunasi, Acanthogobius fiavimanus, Callionymus richardsoni, etc.
ii. Temporary "visitors":
a) Those coming to spawn: Allanetta bleekeri, Ablennes anastomella, etc.
b) Those visiting the area in their young stages only : Decapterus maruadsi, Lateolabrax japonicus, Argyrosomus argentatus, Limanda yokohamae, Kareius bicoloratus, Saurida elongata, Sphyraena pinguis, etc.
iii. Infrequent or accidental "visitors": Conger japonicus, Cololabis saira, Mene maculata, Lateolabrax latus, etc
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5) äž»ãšããŠæ²ã®ç¶²ã«ãã£ãŠæŒç²ããããã®ã¯ïŒãã«ã¢ãžïŒã«ã¿ã¯ãã€ã¯ã·ïŒã€ã·ã¢ãïŒãã³ãžã¯ãã£ïŒãã€ã©ã®çã®éäœã®å°ããéïŒè¥ããã¯è¥å¹Žé矀ã§ãã£ã.æŒç²å°Ÿæ°ã§ç¬¬1äœã«äœãããã«ã¢ãžã¯ãã®99%ãæ²ã®ç¶²ã§æŒç²ããã.
6) 湟å
ã«çŸ€ããªããŠæ¥æ²»ããéçš®ãšããŠã«ã¿ã¯ãã€ã¯ã·ïŒ ãã«ã²ãšãœïŒ ããŠãŽãã€ã¯ã·ïŒã¢ã«ã«ãã¹ïŒãã«ã¢ãžïŒã¹ãºãïŒã€ã·ã¢ãïŒã¡ã€ã¿ã¬ã¬ã€ïŒãã³ã¬ã¬ã€çãèãããã.The whole daily catches by the two masu-ami (a kind of the pound net) operated in Kasaoka Bay were investigated, with reference to the species and size composition, at about weekly intervals during the one-year period from June, I96I through June, I962, for the purpose of clarifying the difference between the catches. These nets, which were selected as the sample out of the many masu-ami operated in this region, were located off Terama village of Konoshima, one 60 m. and the other 350 m. from the shore. Water depths at the locations of these nets were 3.5 and 5.5 m. below the mean water level respectively. There was no significant difference in such hydrographic conditions as water temperature, chlorinity and dissolved oxygen between the locations of the two nets. From comparison of the catches of the two nets, the following results were obtained:
1) The species composition of the catches of these masu-ami showed considerable seasonal variations and local differences.
2) The catch of the nearshore net was, in general, richer in species, greater in weight and fewer in number of individuals than that of the offshore net. The correlation coefficient between the catches of the two nets either in weight or in number of individuals, was highly significant except in August and September.
3) The number of the captured species was relatively numerous in July and August when water temperature was high. Thereafter, it gradually decreased with the falling water temperature, and remained nearly constant during November and December. The species composition of catches of the two nets, however, always differed from each other.
4) The fishes, larger in size and higher in market value in the catches of masuami, such as Mylio macrocephalus Mugil cephalus and Liza haematocheila except Platycephalus indicus were mainly caught by the nearshore net and seldom came into the offshore net. The number per haul of these fishes was usually small.
5) A large number of young Decapterus maruadsi were caught almost exclusively by the offshore net, practically none of them appeared in the catch of the near shore net. They occurred in Kasaoka Bay in large schools from July through October.
6) There was an indication that small-sized or young fishes are taken more numerously by the offshore net than the nearshore net.
7) The following fishes were presumed to come into Kasaoka Bay in schools. They are Engraulis japonia, Saurida elongata, Allanetta bleekeri, Sphyraena pinguis, Lateolabrax japonicus, Argyrosomus argentatus, Limanda yokohamae and Kareius bicoloratus
Fisheries in Hashiri-shima : III. Studies on small-sized crabs found in catches of small trawlers part 1.
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ããŸãïŒæ¥éæé€çãšå¢éçãšã察æ¯ãããŠã¿ããšïŒåæ§ãªæ£ã®çžé¢é¢ä¿ãèªãããã. ãã®é¢ä¿ããïŒã¯ã«ããšãã®äœéç¶ælãå¿
èŠãªé€æéã¯ïŒäœéã®2-3% ã«ãããããšãããã£ã.
ãã¢ãµãªïŒã«ãæ··åæäžçŸ€ã«ãããã¯ã«ããšãã¯ïŒããããã®é€ã®æ··åæ¯çã«å¿ããŠæé€ããããšãæãããšãªãïŒãã®2æ§é¡ã®é€ælãé¢ããéãã§ã¯ïŒæé€ã«ãããé€ã®éžææ§ã¯ããŸãèªããããªãã£ã.Many useless benthic animals are contained in the catches of small trawlers. Small crabs are one of these unutilized resources. Attempt was made to use these animals as food in rearing of the Kuruma prawn, Penaeus japonicus BATE. The experiment was carried out using these small crabs and clam meat during low-temperature season from late October to late December, 1964.
Comparison of the growth between the two groups fed on clam meat only and on the mixture of clam and crabs, respectively, clarified that the latter group grew more rapidly than the former. Molting was observed only at temperatures above 15°C. in both groups.
A positive correlation was shown between the feeding rate per day and the mean temperature of 10-day period; namely, at 12°C., the feeding rate was as low as about 2%, and with the elevation of temperature, especially above 16-17°C., increased remarkably.
Furthermore, the correlation between the feeding rate per day and the growth rate was also positive, revealing that the daily ration necessary for the maintenance of body might be 2-3 % of the body weight.
The prawn fed with the mixture of clam and crab meat took the two kinds of food in approximately the same clam/crab ratio as was given. This fact seems to show that in the feeding of the prawn there is no selectivity as to the two kinds of food
Fisheries in Hashiri-shima : II. Spawning of a file-fish, Navodon modestus (GÃNTHER)
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ã§èŠ³å¯ããããããªåŒ·ãç²çæ§ã瀺ããªãå¯èœæ§ã®ããããšã瀺åãã.A study was carried out to clarify the spawning of a file-fish, Navodon modestus (GÃNTHER), in the Bingo Nada area, as a serial study on the spawning ecology of the commercially important fishes in the central part of the Inland Sea of Japan.
As described in previous paper, the file-fish are caught abundantly by the masu-ami, a kind of pound net, in Bingo Nada, operated during the three months from April until June. Since most of the fish in these months have well developed gonads, they are considered to be spawners.
Observations on ovaries of several samples taken at different times from March through May indicated a rapid development of ovaries during the period. From the analysis of the frequency distribution of diameter of ovarian eggs, the spawning of Navodon modestus may occur at least more than once during the spawning season.
On the basis of the catch records and from the nature of the eggs of the aluterid fishes in general, it was presumed that the file-fish may spawn somewhere along the coasts of islands in Bingo Nada. Efforts had been devoted to find the eggs spawned in nature, especially in Sargassum zones along several islands. A large amount of Sargassum, together with the bottom sediments nearby, were collected at low water and thoroughly examined. Finally, in early June, 1963, 92 eggs were found among Sargassum serratifolium collected near St. I, located at south-western coast of Hashiri-shima.
These eggs were identical in structure and size with the eggs of Navodon modestus obtained by artificial fertilization. It was thus made clear that some of the file-fish may spawn in Sargassum zones.
A consideration was given on the possibility that the eggs of Navodon modestus may not so firmly adhere to substrates in nature as in the laboratory
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šãç£çåµã¯æ¡éã§ããªãã£ã.1) In order to make clear the fecundity and spawning of a puffer, Fugu rubripes T. et S., investigations were carried out in the central waters of the Inland Sea of Japan in April-May, I960-I961.
2) Distribution of the fishing grounds of Fugu rubripes in Bisan Strait was shown.
3) Morphological characteristics of the spawners of Fugu rubripes were clarified. Sex-ratio (female: male) of the spawners caught by seine-nets was approximately 1: 3. Females were significantly greater in weight than in males, while the difference in total length between both sexes was not significant.
4) Development of ovarian eggs seems to be advanced uniformly within an ovary, which makes reasonable to consider that the spawning may occur at a time or at least in a very short period.
5) Relationships of fecundity with total length and weight of body were clarified.
6) Successful collection of the eggs deposited on natural spawning beds was made. The data obtained in the present investigation show that the spawning beds of Fugu rubripes lie in the bottoms having particle-size of sand 2-4 mm. in diameter