A histology-based fish health assessment of farmed seabass (Dicentrarchus labrax L.)

Abstract

The aim of the present study was to assess the health status of farmed seabass (Dicentrarchus labrax L.) using as a tool the histological semi-quantitative system proposed by Bernet et al. (1999). Gills, liver, kidney and intestine were fixed and processed for histological analysis using standard techniques. Organ index values were determined and used to classify the severity of histological response using classes based in the scoring scheme proposed by Zimmerli et al. (2007). The gills were the most histologically affected organ with 56.7% of the fish presenting severe histopathological alterations consisting mainly of hyperaemia, hypertrophy, hyperplasia and necrosis. The kidney was the organ which in most of the fish (58.6%) presented a normal tissue structure. Nevertheless hyperaemia, vacuolar degeneration of renal tubules, necrosis of the haematopoietic interstitial tissue and nephrocalcinosis were observed in some specimens. 71.4% of the fish showed normal or slightly modified liver but hyperaemia, high vacuolization and hypertrophy of hepatocytes were observed in some cases. In general the histology of the intestine was normal or presented slight enteritis. Statement of relevanceThe aim of the present study was to assess the health status of farmed seabass (D. labrax L.) using as a tool a histological semi-quantitative system. This tool is being extensively used in wild fish to assess aquatic pollution but rarely applied in farmed fish.