The estuarine movement patterns of Mugil cephalus (Mugilidae) in response to Harmful algal blooms (HABs) was investigated in the eutrophied Sundays Estuary on the warm temperate coast of South Africa. The movements of six tagged M. cephalus (31–35 cm FL) were manually tracked using a Vemco VR100 acoustic receiver over 27 days during the typical summer bloom period. Fish were released above, within and below the mesohaline zone where Heterosigma akashiwo bloom maxima are known to occur. Physico-chemical variables and chlorophyll-a biomass were collected at each fish location and at four bloom monitoring sites, which locations were based on surface water salinity of 18, 10, 8 and 5. Mugil cephalus mostly occupied the upper mesohaline to lower oligohaline zones moving with the tidal ebb and flow. Phytoplankton biomass peaked at sites with a salinity of 10 and 8, with tagged fish only briefly (<0.63% of total time free roaming) venturing into bloom maxima areas. This is the first account of small scale intra-estuary movements of a mugilid worldwide and also the first to suggest avoidance behaviour of estuarine fishes in response to HABs. More work is needed to further understand how anthropogenic threats may impact the movements of important estuarine-dependent fish species in order to prevent the possible loss of ecosystem services induced by eutrophication.

在南非暖温带海岸富营养化的星期日河口调查了Mugil cephalus (Mugilidae) 响应有害藻华 (HAB)的河口运动模式。在典型的夏季盛开期间，使用 Vemco VR100 声学接收器在 27 天内手动跟踪了六个带标签的M. cephalus (31-35 cm FL)的运动。鱼类被释放到已知发生Heterosigma akashiwo爆发最大值的中盐碱带的上方、内部和下方。在每个鱼类位置和四个水华监测点收集物理化学变量和叶绿素a生物量，这些位置基于18、10、8和 5 的地表水盐度。Mugil cephalus大部分占据了随着潮汐涨落移动的中盐碱带到低盐碱带。浮游植物生物量在盐度为 10 和 8 的地点达到峰值，标记鱼仅短暂地（<总自由漫游时间的 0.63%）冒险进入盛花期最大值区域。这是对世界范围内鲭鱼小规模河口内运动的首次描述，也是首次提出河口鱼类为应对赤潮而采取的回避行为。需要做更多的工作来进一步了解人为威胁如何影响依赖河口的重要鱼类的迁移，以防止富营养化可能导致的生态系统服务丧失。