抄録
The authors reported previously (TANAKA et al 1985) that an abundance index of schooling
fish can be estimated by the records of echo sounder.
The index of the abundance of fish which distributed around the artificial reefs was examined
using the echo sounder. Surveys were carried out in day and night time around the artificial reefs
off Izumozaki during June and September in 1982.
The results obtained are as fo11ows:
1. Fish school recorded on the echogram could be divided into two types, such as one in surface
and middle layer, and another in bottom. In the case of surface and middle layer, any difference
in abundance of fish between the artificial reefs and natural fields could not be found. But in the
case of bottom, fish schooIs distributed more abundant around artificial reefs than in natural fields.
2. Species name of the fish distributed around the artificial reefs was esteemed by test fishing of
gill-net and angling. In June, the school was consisted of the Sardine Sardinops madlanosticta, which
was dominant species, Japanese ahchovy Engraulis japonica and Hairtail Trichiurus lepturus. On
the other hand, in September, the school were consisted of Japanese anchovy, which was dominant
species, Japanese horse mackerel Trachurus trachurs and Yellow tail Seriola quinqueradiata.
