Animal Health, Welfare and Biosecurity

Stress and the environment

Low dissolved oxygen, ammonia, nitrite, temperature extremes, crowding, rough handling and poor nutrition all stress aquatic animals and weaken their defences. Most disease outbreaks follow a period of environmental stress. Managing water quality is therefore the first act of health management.

Biosecurity principles

• Exclude: screen and, where possible, treat incoming water; source seed from reputable hatcheries with health documentation; control visitors and vehicles.
• Contain: dedicate nets and equipment to each unit; disinfect between uses; manage birds, crabs and other carriers.
• Monitor: observe behaviour and feeding daily; sample animals periodically; record mortalities.
• Respond: isolate affected units, seek diagnosis quickly and dispose of mortalities safely.

Observation and early signs

Reduced feeding, gasping at the surface, abnormal swimming, colour changes, lesions, fin erosion, swollen abdomens and increased mortality are warning signs. Daily observation by a trained person is the most reliable early-warning system available to any farm.

Diagnosis and responsible treatment

Treatment without diagnosis wastes money and may be harmful. Fisheries departments, universities and private laboratories offer diagnostic services. Where medicines are necessary, they should be used under professional guidance, at the correct dose, respecting withdrawal periods and legal restrictions. Antibiotics banned for aquaculture use must never be applied; residues result in rejected consignments and lost markets.

Welfare

Fish and crustaceans respond to their environment and handling. Appropriate densities, gentle handling, adequate oxygen, suitable feed and humane slaughter methods are elements of good welfare and also of good product quality. Welfare expectations in export markets are increasing.

Health records

Records of seed source, water quality, feeding, observations, treatments and mortality allow patterns to be recognised and support traceability. They are also increasingly required by buyers and certification schemes.