Studies on perispawning mortalities in brown trout (Salmo trutta L.) from Loch Leven, Kinross, Scotland

Investigations into perispawning mortalities in the brown trout (Salmo trutta L) population of Loch Leven, Kinross, revealed that death occurred as a result of infection with a particular species of Saprolegnia diclina Humphrey type 1. Increased surface area of infection was correlated with a decrease in ion and protein content of the blood and was further reflected by changes in the electrocardiogram pattern. These changes were essentially a widening of the QRS complex with inflection of the RS component, changes consistent with a decrease in certain ions in mammals. Histological changes associated with sexual maturity and fungal infection are described and compared with changes resulting from the administration of androgens to brown trout