Health of cobia

Malformations

Malformations such as notochordal axis syndromes and pericardial oedema may be expressed in early cobia larvae (1–2 days post hatch) and contribute to high mortality rates.

Bacterial disease

Rigorous on-farm water quality and health monitoring programs should be in place for early detection of disease.

Avoid larval rearing in water low in salinity and/or high in fine suspended solids to prevent respiratory stress and epitheliocystis outbreaks (18–35 days post hatch) caused by intracellular bacteria. Early detection and treatment of epitheliocystis with medicated feeds improves survival.

Parasites

The parasitic dinoflagellate Amyloodinium ocellatum and monogenean parasites such as Neobenedenia girellae may affect early juveniles, harvestable-sized fish, and broodfish. Initial signs are associated with lethargy and changes to feeding behaviour. Repeat treatments for re-infestations may be necessary in semi-closed systems like recirculating tanks or ponds. This is because some types of parasite eggs are resistant to treatment and persist in the culture environment.

Nutrition

Cobia have high nutritional requirements. Deficiencies or excesses can lead to disease and reduced growth performance.

Taurine deficiency is associated with:

• green liver
• kidney inflammation
• bacterial infection by Photobacterium and Vibrio species.

Elevated dietary lipids can cause pancreatitis and increased visceral fat.

Note: Many chemicals used in aquaculture, including immersion and oral medications require veterinary advice and prescriptions before use.

Intersex

Cobia were the first reported gonochoristic fish species in Australia to exhibit intersex gonads. This reproductive anomaly is likely a result of endocrine disruptors present in intake waters. The occurrence can severely impact productivity.

Resources are wasted on maintaining individuals in broodfish populations that are not sexually productive.

Intersex also suppresses sexually dimorphic growth where female cobia otherwise grow significantly faster than males after reaching 2kg. Monosex culture of females could lead to substantial productivity gains for cobia aquaculture.

Also consider…

• Learn how to detect epitheliocystis (PDF, 2.6MB).
• Read about detection and management of Amyloodinium (PDF, 5.3MB).
• Read about the occurrence of intersex and sexual dimorphism in cultured cobia.