Journal of The School of Marine Science and Technology,Vol.3 No.2
Ecological and Genetic Characteristics of Common Rockfish,
Sebastiscus marmoratus in Shimizu harbor, Shizuoka
Hiromichi YATOMI, Tomonori MIYAGAWA and Masashi AKIBA
Abstract
Total length of 187common rockfishes, Sebastiscus marmoratus collected in Shimizu harbor ranged from 10.5-
24.2cm. From the results of total length composition, sex ratio and condition factor, the life cycle of adult fish is
divided into two stages:April〜September and October〜 March. In April〜 September, small individuals appear,
males are more abundant and the condition factor increases as a result of active feeding. Therefore, this period is
a time of recruitment and individual growth.During October〜 March,females are more abundant,large individuals
with high gonad-somatic index appeared and larvae were produced.This period,therefore,is a time of reproduction.
Data from Shimizu harbor,such as relative growth,growth formulae,age and maturation were compared with
the Kyushu and Setonaikai regions. The data on morphology and ecology indicate that there are quantitative and
seasonal differences between the sites.However,the results of distinguishing the group clearly were no obtained.In
particular,fish from Shimizu were more similar to Kyushu region.Genetic variability of Shimizu fish was compared
with that of fish from Megi Island in Kagawa Prefecture, but statistically significant difference was not found.
However,it was shown that the uniformity of fish from Hinode wharf was lower than that of fish from Miho marina
in Shimizu harbor. From these results, it is apparent that fish from Shimizu harbor and the Kyushu and Setonaikai
groups are close relations and there does appear to be genetic exchange between these groups.