Changes in protease activity in the skin surface mucus of Atlantic salmon (Salmo salar) during sea lice (Lepeophtheirus salmonis) infestation

Skin surface mucus contains a number of biologically active substances, including proteinases, shown or suspected to have a role in the innate (nonantibody) defence system of fish. The objective of this study was to determine whether proteinase activity in the skin surface mucus of fish is altered as a result of L. salmonis infestation. In 2 experiments in which S. salar were infested with L. salmonis, samples taken from infested fish showed increased proteinase activity compared to controls using 2 different assay methods. In particular, zymography of samples from infested fish showed a series of low molecular weight (17-20 kDa) proteinases that were not present in control samples..