The Atlantic salmon (Salmo salar) genome contains 10 chitinase encoding genes, but little is known about the function of these chitinases. Three of these genes have earlier been shown to be expressed in the stomach tissue. In the current study we show that the protein products of these genes, the family 18 glycoside hydrolase (GH18) chitinases SsChi18-3, SsChi18-4 and SsChi18-7, are secreted to in the stomach mucosa and are amongst the most abundant proteins in this matrix.