日本水産学会誌
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
1994年宇和島湾周辺で発生したGonyaulax polygramma赤潮の環境特性と魚介類の大量斃死
小泉 喜嗣河野 慈敬松山 紀彦内田 卓志本城 凡夫
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1996 年 62 巻 2 号 p. 217-224

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A red tide of long duration (late August to mid November) of Gonyaulax polygramma Stein occurred in and around Uwajima Bay in 1994. This red tide caused mass mortalities of cultured and natural fish and shellfish stocks worth more than 8 hundred million yen.
The maximum density of G. polygramma reached 6.8×104 cells/ml in Uwajima Bay. From fluorometric measurements, it is supposed that G. polygramma cells existed in the surface layer in the daytime and migrated to the bottom layers at night.
During the red tide, oxygen deficient water was formed and eventually the whole water column became anoxic in the coastal waters of Uwajima Bay and Hoketsu Bay. It seems that the death of fish and shellfish was mainly attributable to the anoxic waters with high sulfide and ammonia concentrations caused by the decomposition of G. polygramma cells.
The bloom of G. polygramma in Uwajima Bay was initiated in the Yoshida area, and then the bloom gradually spread to the southern areas of the bay. Analysis of this mechanism of the spread of G. polygramma cells throughout the bay will help to establish a monitoring system for future blooms.
Meteorological and hydrographical data suggest that little rainfall, high water temperature and a low water exchange rate enhanced the initial occurrence and long duration of the red tide of G. polygramma.

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