Respiratory stress in rainbow trout dying from aluminium exposure in soft, acid water, with or without added sodium chloride.

Rainbow trout exposed to 32 μM aluminium at pH=5.0 in artificial soft water ([Ca(++)]=50 μM), with or without added sodium chloride (150 mM), suffer from severe respiratory stress characterized by hyperventilation, low PaO 2, high PaCO 2, low pHa and high blood lactate concentrations at death. Plasma chloride concentration at death had decreased in the group with no added NaCl, but not in the presence of added NaCl. Median survival times were not significantly different in the two groups. These findings suggest that death under the given conditions is primarily due to impeded gas exchange.