What is 'swim bladder inflammation' (SBI) and what should I do if I think my fish has it?
The swimbladder evolved from the primitive lungs of fish, and it acts as a 'buoyancy aid', so that the fish can maintain itself the right way up in the water. The gas-filled swimbladder occupies from 5 to 7% of the total body volume of fish. To maintain neutral buoyancy (i.e. to stay down in the water at the same position), the volume of the swimbladder has to be altered as the fish swims to higher or lower depths. This is because the water pressure changes at different depths. The fish either swallows air or it secretes and absorbs gas through specialised regions of the swimbladder wall.
SBI usually affects fish in their first summer, and the signs include:
- Abdominal distension
- Loss of balance
The infection is a viral disease that is part of the Spring Viraemia of Carp (SVC) and It is the most important viral disease in ornamental, wild and farmed carp as well as other fish species. The infection can spread rapidly, and may develop into a secondary bacterial infection.
The affected fish should be isolated as soon as possible, perhaps in a quarantine tank to try and halt the spread of the disease to unaffected fish. Although the viral infection cannot be treated, any secondary bacterial infection may need antibiotic therapy.
It is important to call your vet to discuss the fish's condition. The vet may need to assess the severity of the problem.
Remember that most diseases affecting fish have a very strong stress component, so avoiding or minimising stress is an integral part of prevention or recovery. It is often better not to stress fish still further by moving them to a treatment tank. If the treatment might be harmful to an established tank, think about carrying out any treatments in the quarantine tank.
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