Growth, maturation and mass mortality of Konosirus punctatus in Lake Shinji, a coasta lagoon, Japan
2005
Ishitobi, Y.(Shimane-ken. Inst. of Public Health and Environmental Science, Matsue (Japan)) | Hiratsuka, J. | Kuwabara, H. | Yamamuro, M. | Nakamura, Y. | Moriwaki, S.
In order to know the growth and maturation of Konosirus punctatus in Lake Shinji, monthly examination was carried out. Fishes were collected using a set net at the western end of the lake from March 2002 to March 2003. Large, medium and small size groups of K. punctatus occurred in March, April and July, respectively. The large group collected from March to June was divided into two groups. We found 4 age groups of K. punctatus from the frequency distribution in standard length. Spawning season was estimated to be from May to June from the seasonal change in GSI. Condition factor (CF) of the large and medium groups decreased after the spawning season to September. The large group exhibited greater decrease in CF than the medium group, but no decrease in the small group. Mass mortality of K. punctatus occurred in June 2002 when GSI rapidly decreased. It was confirmed that K. punctatus died when the bottom layer was not in anaerobic conditions. The large size fish occupied a larger part of dead fish than the medium fish. The mortality was considered to be closely related to spawning and decrease in CF.
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