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Experimental Transmission of the Fungus Phoma herbarum to Chinook Salmon
Author(s) -
Burton Tamara O.,
Meyers Theodore R.,
Starkey Norman S.,
Follett Jill E.
Publication year - 2004
Publication title -
journal of aquatic animal health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 52
eISSN - 1548-8667
pISSN - 0899-7659
DOI - 10.1577/h03-055.1
Subject(s) - chinook wind , biology , oncorhynchus , phoma , conidium , juvenile , hatchery , fungus , fishery , fish hatchery , fish <actinopterygii> , fish farming , aquaculture , botany , ecology
The fungus Phoma herbarum is an incidental pathogen for salmonid fish, and experimental studies were conducted to determine whether it could be transmitted to juvenile Chinook salmon Oncorhynchus tshawytscha by oral and airborne exposures. Phoma herbarum that had been isolated from juvenile Chinook salmon sustaining a low‐level mortality in a hatchery was grown in the laboratory and quantified using a hemocytometer. The quantified inoculum of fungal conidia was mixed with dry fish food for the feeding studies, sprayed on the surface of the water for the airborne study, and injected into fish to verify the pathogenicity of the fungus. Histological examination revealed no mortality or internal fungal infection in either the oral or airborne exposures. Average cumulative mortality in the replicate groups injected with fungal conidia was 65% in the fingerlings and 56% in the fry, both groups showing clinical signs of hemorrhage and invasion of tissues by visible fungus. Histological examination of injected fish indicated hyphal invasion of tissues with necrosis and inflammatory exudate. The 100% survival of the fish in the oral and airborne exposures and the surprisingly high survival of fish inoculated with fungal conidia indicated that Phoma herbarum is not easily transmissible to juvenile Chinook salmon under optimal environmental conditions.