Abstract
Cultured yellowtail with symptoms of prominent yellow discoloration of the body were histopathologically investigated. Material fish were obtained from two different areas (area A and area B) in Nagasaki Prefecture in 1987.
In gross pathology, the most obvious change of the affected fish from both areas was the prominent yellow discoloration of mouth, orbit and abdominal region. The liver and spleen from the affected fish were enlarged and more breakable than normal. Pale discoloration of the gills was found in the diseased fish.
Histologically, systemic deposition of a ceroid-like pigment and advanced hemolysis were observed in the diseased fish from area A. On the other hand, in the diseased fish from area B, focal necrosis and crystalloid substnces in the liver parenchyma were remarkable in addition to the similar findings observed in the diseased fish from area A.
From the results of histological observations, it was suggested that there would exist larger amount of free fat peroxides in diseased fish showing yellow discoloration than in healthy fish.
