Drifting seaweeds were labeled with post-paid reply cards sealed in polyethylene envelopes and liberated during the spawning season of the halfbeaks, April-June, in 1964. One hundred and fourty two reply-cards from 912 labeled seaweeds were recovered. Halfbeak eggs on drifting seaweeds do not drift a great distance in their incubation period, though they move very intricately in some limited areas. The maximum drift distance of eggs is 27 miles so far as the result is concerned. It is estimated that some 70 per cent of drifting seaweeds and their lives as drifting seaweeds within 15 days (viz. incubation period of halfbeaks). Supposing that each halves of the natural decrease in drifting seaweeds is due to casting up ashore and sinking to the sea bottom respectively, some 35 per cent of the halfbeak eggs are considered to be killed before hatching. There are several places where concentrated cast up of drifting seaweeds is observed. It must be effective to make some facilities along these coasts to prevent drifting seaweeds and halfbeak eggs on them from being casted up.
The aquatic insect communities of two dammed lakes, Yubara Reservoir and Asahigawa Reservoir as well as their inflows and outflows were studied in August 1962. Considerations on the results are summarizied as follows : Standing crop of bottom animals and dominant life form in respect to the speed of current and substratum is as shown in the following table. [table]
Gnathopogon caerulescens (Cyprinidae), about 10cm in body length of the adult, lives only in Lake Biwa, Japan. The main food of this fish consist of planktonic crustaceans. Seasonal migration of the fish was clearly observed : i.e. they are distributed in the hydrophyte area of the inner bay in spring, the bottom layer of the inshore part in summer and the bottom layer of the deepest part in winter. Records of daily catches by several fishing gears, namely a gill net, a trawl and a spawning trap, from 1957 to 1964 were available by the courtesy of the Fishermen Cooperative Associations which are situated around the lake for the estimation of the population density in the present study. Samples of adult or sub-adult were taken monthly from commercial fishing catches by the above mentioned gears between April 1964 and March 1966 and from these sampled specimens the age and other measurements concerning the population dynamics were measured or examined. The mean of the catch per day by the spawning trap in spring may be considered as the index of the spawner population. The main part of the population caught by the trawl in winter is the under-yearling, so that the mean of the catch per day may indicate the population of this stage. As the specimens caught by the gill net in summer consists mainly of the yearling, the mean of the catch per day may be used as the index of the yearling population in summer. The index of the under-yearling population between November and December tends to be proportional to that of the spawner population. From this fact it is suggested that, although there are many distinctive life cycle stages, egg, fry and juvenile, and these stages are supposed to be highly vulnerable, mortality in these stages give little effect on the annual fluctuation of the population density. There is no corelation between the index of the under-yearling population in early winter and that in late winter. Therefore, it is likely that the proportional relation between the size of the biomass of the spawner and their progeny is disordered during winter. So far as the present study goes it can be concluded that one of the causes for the annual fluctuation of the population density rests on the disorderliness between the size of the biomass in early winter and that in late winter. The index of the yearling population in summer seems either to be constant regardless of the yearly change of the index of the under-yearling population in late winter, or to show rather negative correlation with the latter index. Heavy fishing during the spawning season could have a negative effect on the increasing population.
Drei Assoziationen wurden entlang einer Maβlinie fur Schneebedeckung von K. OGASAHARA und seinen Mitarbeitern unterschieden. Grate, die sich schon am Ende April von der Schneebedeckung befreien, sind vom Zwergkierngestrauch (Vaccinio-Pinetum pumilae, Tabelle 3.) bedeckt worden, Hange, die spater ausgeapert und mit Schneewasser etwas getaucht werden, vom Faurio-Caricetum blepharicarpae (Tabelle 1), und die Rander des Pinetums vom sommergrunen Gebusch der Sorbus-Acer-Assoziation (Tabelle 2). Der Nerursachende Faktor ist der Wintermonsun, unter dessen Einfluβ der Schnee sich 69-155cm auf dem Pinetum, 200-390cm auf dem sommergrunen Gebusch der Sorbus-Acer-Assoziation, und 623-657cm auf dem Faurio-Caricetum (nach OGASAHARA und Mitarbeitern am 19. Marz 1964) sammelte. Auβerdem handelt es sich auch um das Mikroklima im Sommer und umdie Wasserbilanz in der Vegetationsperiode wie in Tatra (BRAUN-BLANQUET^<1)> s. 548).
1. The relationship between representative aquatic organisms and water temperature was comfirmed with experiments both in the field and in the laboratory. 2. The rate of decomposition of each species is indicated by the percentage of the dry weight of its remainder to its total dry weight. In the field comparison was made in the seasonal processes in which each material is set. In the laboratory, the processes of decomposition are observed at 5°±1℃, 12°-17℃ (room temperature), 20°±1℃ and 30°±1℃. 3. Each body of these plants and animals was observed to decrease in a hyperbolic curve, but the process of decomposition, when observed by the semi-logarithm, was made more distinct than in a hyperbolic curve. Though the rate of decomposition was affected by changes in temperature, it stagnates at about 40 per cent in the remainders of curcian and crawfish, for almost nothing but skeleton and crust remains. In the water-flea (Daphnia, Cyclops) their crust is so soft that it is much affected by water temperature, and decreases in a straight line. The flesh of animals disappears within 10 days at 30℃, and within 50-60 days at 5°-10℃, but it is estimated from the results of experiments that their skeleton and crust require several years or more than 10 years. 4. The decomposition of plants requires a longer time than that of the animals. Even in such soft materials as Spirogyra 10 per cent of their bodies are found remaining at 30℃ after the passage of 100 days, and so it takes about 2000 days for the stem of a reed to disappear. Generally the submerged and floating-leaved vegetation die in autumn and therefore most of their bodies cannot complete disolution into water before the year-end and so they are carried over the winter as detritus. 5. The decomposition rate of materials in bottles in the laboratory are slower than that of the same materials in the field. The value of pH, disolved O_2,NH_4-N, PO_4-P and KMnO_4 con. in water were measured in the course of decomposition. From the results it is found that the condition of water is similar at each stage of decomposition in spite of the differences both in the changes of temperature and in the rate of decomposition.
The seasonal change of the longevity of the worker honeybee (Apis mellifera LINNE) in Sapporo, was studied by the marking method. Three seasonal groups, spring bees, summer bees and autumn bees, are distinguished, respectively, with the estimated mean longevity of 30-40,25-30 and 50-60 days. The wintering bees are, as already well known, characterized by the prolonged longevity. The general trend is similar to that given by previous records, especially by Free and SPENCER-BOOTH (1959), excluding the difference due to the short favorable season characteristic to Sapporo. Foraging and brood rearing activities are regarded as important factors affecting the life-span, the former acting directly, whereas the latter indirectly by stimulating the foraging activity.
1. This report deals with the roosting flock area and flight line of the Eastern Carrion Crow and Japanese Jungle Crow living in the Zenkoji basin in the northern part of Nagano Prefecture in autumn and in winter during the years from 1963 to 1964. 2. The crows belonged to the following three roosting flock areas, Nojiri, Sanseiji and Nukazukayama, each being influenced by the lay of the land. 3. It was found that the flight line was in the lowest part of the area like a valley or above the river, making use of the natural features. 4. The roosting place of the crows in the Zenkoji basin was observed to show seasonal variation. No breeding bird's roost was observed in the breeding season, and both autumnal and winter roosts were observed in the non breeding season. 5. In the heavy snow district at the north of the Zenkoji basin, when the snow accumulated heavily and continued for a long time the winter roost was moved from Lake Nojiri to Inoue in the suburbs of Suzaka City. 6. The seasonal variation of the roosting place of crows is to be published at another occasion.