RECOVERY OF THE ECHINOMETRA POPULATION IN THE INTERTIDAL ZONE IN THE VICINITY OF SETO, WITH A PRELIMINARY NOTE ON THE MASS MORTALITY OF SOME SEA URCHINS IN THE SUMMER SEASON

Abstract

I reported1l the mass mortality of Echinometra mathaei (BLAINVILLE) occurred in the winter 1962-63 and suggested that the unusual cold weather of that winter was responsible for it, but I could not affirm this at that time. However, several papers reporting the biological effects of that severe winter have been published in Japan l and Europe, and these seem to justify my supposition in a way. Since I wrote that report, I have tried to visit the shores whenever there are any chances, especially in the season from spring to summer when the tide is bigger in the daytime, to know how the Echinometra population has recovered in the intertidal zone. At the same time I have endevoured to get any informations concerning the occurrences of striking tropical or subtropical invertebrates in this vicinity in these two years, during this period the winter was never so severe as in 1962-63. The results of those sporadic observations and the fragmental knowledges obtained are here arranged in a form of a short note as seen next. In addition, a brief note is given as to the mass mortality of some echinids in the summer season.