The occurrence of the ciguatera fish poisoning (CFP) causative Gambierdiscus spp. was confirmed in the Sea of Japan for the first time in 2009. This paper reports seasonal distribution of Gambierdiscus spp. and epiphytic diatoms in the Sea of Japan. Monitoring results suggested an antagonistic interaction in abundances between epiphytic diatoms and the dinoflagellate Gambierdiscus spp. Allelopathic effects of diatoms were considered to be involved in the competitive phenomenon. Therefore it is hypothesized that cell densities of epiphytic pennate diatoms on macroalgae are a novel determinant affecting the abundance of Gambierdiscus spp. other than sea water temperature, salinity and nutrients. Monitorings of the abundance of epiphytic diatoms would lead us to predict the occurrences of Gambierdiscus spp. blooms in the CFP area, and thereby the CFP risk assessments would be developed. Phylogenetic analyses indicated that Gambierdiscus spp. in the Sea of Japan belonged to Gambierdiscus sp. type 2 which was reported to be non-toxic. Nevertheless, based on morphological characteristics, at least two types of Gambierdiscus spp. were found in the Sea of Japan. It is needed to test the toxicity of the both types of Gambierdiscus recognized in the present study for evaluation of the probability of CFP outbreak risks in the Sea of Japan in the future.

雪茄鱼中毒（CFP）的致病菌Gambierdiscus spp的发生。2009年首次在日本海中得到证实。本文报道了Gambierdiscus spp的季节性分布。和日本海的附生硅藻。监测结果表明，附生硅藻和鞭毛鞭毛藻Gambierdiscus spp之间存在大量拮抗作用。硅藻的化感作用被认为与竞争现象有关。因此，可以假设大型藻类上的附生戊二烯硅藻的细胞密度是影响甘比氏菌丰富度的新决定因素。spp。除了海水温度，盐度和营养素。监测附生硅藻的丰度将使我们能够预测Gambierdiscus spp的发生。在CFP区域开花，因此将开发CFP风险评估。系统发育分析表明，Gambierdiscus spp。在日本海中属于Gambierdiscus sp。据报道是无毒的2型。然而，基于形态学特征，至少有两种类型的甘比氏菌属（Gambierdiscus spp）。在日本海中发现。需要测试两种类型的甘比双球菌的毒性 在本研究中得到认可，可用于评估未来日本海中CFP爆发风险的可能性。