抄録
During the period from October 1953 to March 1954 innumerable number of starfish, Asterias amurensis, made a sudden attack on the clam beds along the coast of Tokyo Bay and devoured large quantities of cultured clams. At that time the spawning season of these starfish was inferred to be either May or July from the fact that the same species spawns in these months in different localities.
However, a series of field surveys consecutively conducted since the outburst of this predator have led us to the conclusion that its spawning season extends frcm January to April with the peak in late February through early March(Fig. 1 and Table 1).
The water temperature in Tokyo Bay during the above mentioned spawning seasonn approximates to that in the coastal waters of Hokkaido in July, when the starfish is known to spawn in this locality(Fig. 3). In addition, young starfish with arm lengths measuring about 5mm. were found in abundance through the early half of March, attaching on the colonies of Styela plicata LESUEUR and Coreila japonica HERDMAN etc. (Fig. 2).
These pieces of evidence may be sufficient to support the view that the majority of this starfish spawn in late February through early March in Tokyo Bay.
