[Gas bubble disease of fish].

Gas bubble disease (GBD), a non-infectious, environmentally/physically induced trauma, is caused by an increase in the dissolved gas pressure above the ambient air pressure (supersaturation). Frequently the cause is an increased partial pressure of nitrogen-especially in spring-/groundwater. All fish species as well as amphibians and aquatic invertebrates are susceptible. Fish species and age groups are different sensitive; swim up fry is very endangered. The disease may occur in a chronic form at approximately 103% and in an acute form at above 110/115% total gas pressure (TGP). Fish, especially fry, with the chronic form die slowly without symptoms. The clinical symptoms of the acute form are disorientation, subcutaneous emphysema, embolism, exophthalmus mostly only on one side, swimming near the water surface with darkened skin, haemorrhages and high mortality. Losses increase with increased TGP. Generally, mortality in the chronic form increases by secondary infections of emphysematous tissue. As technical processes may be the cause for an increased total gas pressure, such as water pumping, heating water or mixing cold with warm water, in this context we could speak from a "technopathy". The following "therapeutic" measurement is recommended: avoid causal factors, transfer damaged fish in expanded water, turn off the cause, compensate the pressure in deeper water, if possible.