Pathological conditions in the liver of ruffe, Gymnocephalus cernua (L.), from the Elbe estuary

Abstract. During a 3-ycar study of the ruffe population in the highly polluted Elbe estuary, 551 fish were examined for grossly visible liver lesions. Three main types of abnormalities were distinguished, and the histological characteristics of representative livers are described. The rate of occurrence of each abnormality was recorded and correlated with the length of the affected fish. The livers in 11%; of the ruffe were uniformly discoloured due to excessive deposition of fat in the hepatocytes. In 39% of the livers, localized pale flecks, patches, or marbled patterns were observed. A subsample examined histochemically revealed that these were also due to fat deposition, except in a few cases resulting from excessive glycogen accumulation. Distinct from these two syndromes were pale nodules in the hepatic tissue seen in 8% of the ruffe. Microscopy showed the nodules to be neoplastic. A relationship between fish length and prevalence was found only in the case of these nodules. Possible causes of the various liver abnormalities found are discussed.