Gas Bubble Disease

Figure 1. Rainbow trout with several gas bubbles in the anterior chamber. Note the haemorrhage both dorsally and ventrally, the latter “coning” through the ventral iris pore

Gas bubble disease (GBD) is the fish equivalent of the “bends” in human scuba divers. It is the result of gas coming out of solution in the bloodstream, thereby leading to the formation of emboli, especially in smaller blood vessels, including rete. Thus, lesions are common in gills, and the choroid gland of the eye. In water that is supersaturated, fish equilibriate with that supersaturated gas, just as human scuba divers equilibriate with gas at high pressures. It is not known precisely what prompts the...