Occurrence of Hematozoa in Atlantic Salmon (Salmo salar) Smolts and Adults in an English River

The percentages of hemoflagellates found in single samples of Atlantic salmon (Salmo salar) from the River Exe, Devon, in 1971 (122 fish) and 1973 (50 fish) were 33 and 32; of hemogregarines, 18 and 22. The percentages for 21 adults taken in the estuary in August 1971 were 14 and 0, respectively; in 9 adults taken in the estuary in March 1972 and in 9 taken in fresh water in November 1971, no hematozoa were found. Statistical analysis of hemoglobin data showed no significant difference between parasitized and healthy fish. Neither the specific identities nor the vectors of the hematozoa were determined.