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 juv enile turbot Colistium nudipinnis and brill, C, guntheri in an experimental rearing facility. Gross signs of disease included loss of appetite, errati c swimming, distended abdomens caused by an accumulation of clear fluid in the stomach and intestines, and haemorrhagic lesions on the underside and b ases of the fins. Histological examination of the liver and kidney showed f ocal areas of necrosis and extensive haemorrhaging. Other lesions included necrosis and sloughing of the mucosa of the stomach and intestine, and spar se vacuolation in the brain and spinal chord. Bacteria isolated from thr li ver, kidney, and spleen included Vibrio splendidus I, and V. campbellii-lik e variants. Examination of the liver, kidney, and brain by electron microsc opy failed to detect the presence of viral particles and samples of brain w ere negative against anti-SJNNV rabbit serum. It appears that the mortaliti es were due to infection by opportunist bacteria in fish predisposed by a c ombination of adverse factors including an acute period of poor water quali ty and perhaps an inadequate diet. (C) 2000 Elsevier Science B.V. All right s reserved.