THE BIOLOGICAL BASIS OF THE ANNUAL SPAWNING MULTIPLICITY OF THE GRASS CARP (CTENOP HARYNGODON IDELLUS CUV. ET VAL.) UNDER ARTIFICIAL CULTIVATION

The technique of multiple spawning of the grass carp is widely practised in artificial propagation. The biological basis consists of:(1) The development of oocytes in the ovary of the brood fish is not completely synchronous. After the first spawning is artificially induced, what remain in the ovaries are some quantities of oocytes of the third phase. These oocytes continue to develop into the fourth phase after a period of intensive feeding of the brood fish. The fish is, then, ready for the successive spawning under artificial propagation.(2) During the period when the oocytes of the third phase develop into the fourth phase there is an active reaction of AKP, but none of ACP. This indicates that the metabolism of these oocytes is in progress.(3) A portion of the basophilic cells in the mesoadenohypophysis retain their secretory granules, indicating that the gonadotropin-secreting activity is still going on. This constitutes the main physiological factor governing the further development of the third phase oocytes into the ripe ova.