Abstract
As the investigation to estimate the abundance of seaweed has been done mainly by diver's
direct sampling, surveying wide area in short time was very difficult. In this paper, a method of
combination of the echo sounding and diver's sampling was considered. Examination of the method
and application to the coastal area of Hamochi, Niigata Prefecture are described.
Obtained results were as follows, :
1. 10 species in 4 families of seaweed were distributed widely in this coast.
2. The abundance of seaweed is closely relating to the type of sea bed. Order of the abundance is,
on the rock, boulder, stone, graval, sand. The abundance of seaweed decreased linearly with the
depth.
3. The length of seaweed by echogram was compared with samples brought by a SCUBA diver.
Both values agreed fairly well, except When the seaweed is longer than 2m. In this case the
seaweed was winding and the record was shorter than the sampled.
4. The abundance of seaweed were estimated from the echogram and the data of sampling by
SCUBA diver. The abundance of seaweed longer than 0.5m were estimated about 3, 580 metric
tons, in the coastal area from Akaiwa to Hamochi fishing port, 3km.
As a result. the new method can be applied to estimate the abundance of large size seaweed.
