Vibrio species associated with mortalities in hatchery-reared turbot (Colistium nudipinnis) and brill (C. guntheri) in New Zealand

Studies were conducted to determine the cause of the acute mortality of juvenile turbot Colistium nudipinnis and brill, C, guntheri in an experimental rearing facility. Gross signs of disease included loss of appetite, erratic swimming, distended abdomens caused by an accumulation of clear fluid in the stomach and intestines, and haemorrhagic lesions on the underside and bases of the fins. Histological examination of the liver and kidney showed focal areas of necrosis and extensive haemorrhaging. Other lesions included necrosis and sloughing of the mucosa of the stomach and intestine, and sparse vacuolation in the brain and spinal chord. Bacteria isolated from thr liver, kidney, and spleen included Vibrio splendidus I, and V. campbellii-like variants. Examination of the liver, kidney, and brain by electron microscopy failed to detect the presence of viral particles and samples of brain were negative against anti-SJNNV rabbit serum. It appears that the mortalities were due to infection by opportunist bacteria in fish predisposed by a combination of adverse factors including an acute period of poor water quality and perhaps an inadequate diet. (C) 2000 Elsevier Science B.V. All rights reserved.