Chattonellosis

Chattonellosis is an acute health issue in marine aquaculture caused by the proliferation of microalgae belonging to the order Chattonellales. These organisms are highly potent harmful algal bloom species that create hazardous conditions for finfish cultivation by releasing neurotoxins and clogging gills with excessive mucus production.

The causative agents are primarily species within the Chattonella genus. These flagellated organisms are classified as raphidophytes. The pathology is driven by the production of brevetoxins, which interfere with the neurological and respiratory functions of aquatic organisms, leading to lethal conditions when these algae reach high cell densities.

Marine species, particularly those in high-density cage cultures, are the primary victims of this disease. Clinical symptoms include gasping at the surface, rapid opercular movement, and sudden mass mortality. Post-mortem examinations often reveal severe inflammation and necrosis of gill filaments, which prevents proper gas exchange and leads to systemic hypoxia.

Development and spread are facilitated by specific environmental triggers, including water temperatures exceeding 20°C, high nutrient loading (nitrogen and phosphorus), and stable water columns with limited vertical mixing. In these conditions, Chattonellales populations can expand rapidly, turning the water column into a toxic environment for fish.

Management and prevention focus on early warning systems and mitigation techniques.

• Routine phytoplankton monitoring to identify bloom initiation.
• Strategic location of fish farms in areas with high tidal flushing.
• Deployment of water aeration systems to disrupt cell aggregation.
• Immediate suspension of feeding to reduce stress on fish during suspected bloom events.