SOME OBSERVATIONS ON GROWTH VARIATION AND FEEDING BEHAVIOUR IN THE FRY OF TWO RACES OF JAPANESE CRUCIAN CARP, CARASSIUS CARASSIUS LINNE

抄録

In the two experimental populations started with each 100 larvae just hatched out of one batch of eggs of the two races of cruclan carp (Kin- and Gengoro-buna) the growth of fry was studied during four months with some observations of feeding habits. 1. The mortality rate of the fry, which was much higher at the earliest period of the experiment than at the later periods, was so low as a whole that almost all the fry survived to the latest period. 2. In the later course the coefficients of variation of body length decreased owing to the increase in growth rate of the smaller group of the fry. 3. By the second month after hatching the relative height of the body to body length of the race Gengoro-buna had become significantly greater than that of the other race Kin-buna. 4. The fry of Kin-buna showed more intensive attacks on tendipedid larvae than Gengoro-buna at about a month from hatching. 5. When alarmed, the Kin-buna fry used to swim rapidly toward the bottom of the aquarium, while the Gengoro-buna fry to the water surface.