An Uncommon Presentation of Fungal Infection in Atlantic Salmon Fry

Abstract

Moribund fry from several families of Atlantic salmon Salmo salar had a conspicuous cranial defect that corresponded with 18.3% (SD, 4.5%) mortality of fry. The lesion was characterized by a domed, epithelium-covered swelling centered over the optic tectum. The swelling was an edematous reaction to the extension of a fulminating necrotizing mycotic stomatitis and bronchitis into the cranial tissues including the ventral meninges. An oomycete is believed to be the pathogen. The percentage mortality of fry in each separately reared family ranged from 1.0 to 63.3%. An analysis of variance revealed that the differences in mortality among families were significant (P < 0.0001), and that the difference between replicates of each family, reared apart, were not significant. A possible genetic basis for resistance to fungal infection is discussed.