Sargassum Vegetation Growing in the Sea around Tsuyazaki, 
North Kyushu, Japan 1 
Tadao Yoshida , 2 Takeo Sawada, and Masahiro Higaki 3 
Ecological studies on the subtidal marine 
vegetation, including the Sargassum community, 
have not progressed far because it is harder to 
make field surveys in subtidal vegetation than 
in terrestrial or intertidal vegetations. Some 
depth records for species of marine algae have 
been obtained using dredges and other instru- 
ments. From these data, we know that there is 
considerable vegetation developed at subtidal 
depths (cf Ueda and Okada, 1938, 1940). 
Walker (1947) carried out extensive studies 
of the Laminaria beds around Scotland. His at- 
tention has been centered chiefly on productiv- 
ity. Underwater observation of seaweeds has 
been done from time to time in the course of 
the development of diving apparatus. Waern 
( 1952) published the results of his underwater 
survey of seaweeds. More recently Gilmartin 
(I960) carried out a survey of the deeper water 
algae of Eniwetok Atoll with the aid of a 
self-contained underwater breathing apparatus 
(SCUBA). Above all, a work published by Gislen 
(1930) is the most remarkable. He proposed a 
system of classification of life-forms for benthic 
plants and animals, and described many "as- 
sociations.” When these works are examined 
from a phytosociological point of view it is 
noticed that they are prescribed by the state of 
progress in terrestrial plant ecology at the par- 
ticular time of writing. For example, Gislen 
only recognized associations in the concept of 
Swedish school and based on data from but a 
few quadrats. 
Artificial stone beds have been laid down on 
shallow bottoms at many places around Japan 
for the propagation of useful algae, such as 
1 Contribution from the Department of Fisheries,: 
Faculty of Agriculture, Kyushu University. Manuscript 
received November 23, 1961. 
2 Tohoku Regional Fisheries Research Laboratory, 
Shiogama, Japan. 
3 Department of Fisheries, Faculty of Agriculture, 
Kyushu University, Fukuoka, Japan. 
Gelidium and Undaria. In order to evaluate the 
usefulness of these artificial stone beds many 
surveys have been carried out on the communi- 
ties of algae developed upon them. However, 
the data secured from them are too rough to 
provide satisfactory knowledge of the marine 
vegetation and succession in its populations 
(Katada, 1958). 
Many concepts and methods for the analysis 
of vegetational structure have been proposed 
recently in the course of the development of 
phytosociology. In contrast to the method of 
classifying the plant communities used by 
Rraun-Blanquet and others, Goodall ( 1953) in- 
troduced a new statistical method for classifica- 
tion using positive interspecific correlation be- 
tween the species as a criterion. On the other 
hand, Whittaker (1956) and others developed 
the concept of a vegetational continuum. These 
are applicable to the study of marine algal vege- 
tations. 
A Sargassum vegetation covers large areas of 
the upper subtidal region of the warmer waters 
around Japan. This vegetation affords a good 
habitat or spawning bed to many kinds of fish. 
Plants of Sargassum and its allied genera, float- 
ing at the sea surface after being detached from 
their substrata, are known as "floating seaweeds” 
or "nagaremo.” The floating seaweeds and many 
kinds of fish exist in a close relationship insofar 
as the fish spawning and growth of the larvae 
of the fish are concerned. The authors have been 
engaged in the survey of the floating seaweeds 
for several years, and feel acutely the necessity 
for knowledge concerning the Sargassum com- 
munity from which the floating seaweeds of Ja- 
pan are derived. The authors carried out a 
survey on the Sargassum community growing 
on the rocky shallow sea around Tsuyazaki, 
north Kyushu, Japan, and intend to analyse here 
the relationship of species populations to the 
gradient of environmental factors. 
135 
