Gill structure of cultured Salmo trutta fario related to sampling technigues

Abstract

A scanning electron microscope and histological study of the trout Salmo trutta fario gill was undertaken following 3 different killing techniques (concussion, decapitation and prolonged anesthesia with MS 222) and 2 different fixation procedures (glutaraldehyde and formaldehyde). 50% of fish killed by concussion and 20% of fish sacrificed by decapitation displayed gill lamellar dilations (telangiectasis), whereas no anesthetized fish showed altered gill structure. No differences could be detected when comparing the effects of the 2 fixatives. We conclude that salmonids should not be killed either by concussion or decapitation if gills are to be examined histologically.