SEASONAL PREVALENCE AND INTENSITY OF INFE CTION WITH CERATOTHOA-GAUDICHAUDII IN SALMON (SALMO-SALAR) CULTIVATED IN SEA-WATER IN THE SOUTH OF CHILE

In order to provide information about Ceratothoa gaudichaudii as a par asite of Salmo salar cultivated in sea water, 800 salmons obtained fro m two fish farms located in Calbuco (41 degrees 45'S; 73 degrees 45'O) and Huelmo (41 degrees 41'S; 73 degrees 03'O) 10th Region, Chile, wer e sampled monthly from July 1990 to December 1991. The parasites were found on the branchial archs of the mouth (77.7%) and on the branchia (14.1%) of the salmonids. In both fish farms, the monthly prevalence o f parasited salmon was at harvest, 56 and 100%, with and average of 1. 33 and 3.5 parasites per parasited fish. A marked increase of the size of all parasites was observed during the months with a mean monthly s ea-water temperature higher than 11 degrees C. The role of native fish as a source of salmon infection is discussed.