Sampling artefacts in gill histology of freshwater Atlantic salmon (Salmo salar)

Fish gills are delicate structures, which are vulnerable to damage from pathological as well as non-pathological aetiologies. They are frequently sampled for histology as they are involved in many recognised disease processes. Artefacts, arising from sampling techniques, can potentially interfere with interpretation of gill histology. A range of possible processes that can result in sampling artefact were assessed in a group of freshwater Atlantic salmon (Salmo salar) pre-smolts. A range of histopathologies resulted, illustrating how critical both sampling efficiency and careful tissue handling are for optimal tissue sections to enable accurate histopathological interpretation.