びわ湖における陸封型アユの変異性に関する研究 : II.集団の分化と諸変異について

概要

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The mode of life and the morphological characters of the Ayu-fish in the advanced phases after the group formation were studied with special reference to the comparison between their groups. The stream population of the Ayu used to eat zooplankters in the lake, but suddenly changed the food-habit exclusively to adherent algae in the inlet streams. They can be classified into two groups based upon the time of stream ascending and body size. Namely, a group which ascends streams before late-spring and are of relatively larger body size, and another group which ascends streams after late-spring, and are of comparatively smaller size. The lake population of small body size tends to eat zooplankters throughout their life. The lake population of large body size prefers to live at rocky shelves and to eat mainly adherent algae. The fish of the lake population of large and small body sizes were of the typical standing water form. while those of the early ascending group of the typical running water form. The body form of the fish of the late ascending group was intermediate between those two forms in size. There were also significant differences in the numbers of rays of the dorsal and anal fins, among the populations. Several discussions are presented on the relation between the variations in each population and the environmental conditions at the early stage of development of the fish.
日本生態学会の論文
1973-06-20