A larva of the nematode Hysterothylacium sp. was found in one specimen of Coho salmon. A total amount of 120 samples of Coho and Atlantic salmons and trouts were collected for parasitological and pathological analysis from the marine culture cages in Calbuco and Chiloe, X Region, Chile. Hysterothylacium sp. which matures in the digestive system of the teleost fishes was extracted from the gills. This parasitism is uncommon in farmed fish due to its type of food, because the industrial dry pellets, given ad libitum, avoids the entry of indirect life cycle parasites. A hypothesis is given to explain the presence of the nematode in the salmon.