Histopathological comparison of gill lesions of rainbow trout in extensive and intensive culture systems

Abstract

The direct contact of the fish gill with water makes it one the most susceptible organs of the fishes where microbial and chemical water pollution causes pathological lesions to the gill. We studied the variety and abundance of gill lesions of rainbow trout and compared them between extensive and intensive culture systems. We selected four farms of rainbow trout culture in East Azerbaijan province, two extensive and two intensive culture farms and collected 384 gill samples from each culture system in autumn 2006. After gross examination, representative sections of the gills were fixed immediately in 10% neutral buffered formalin, processed routinely, and embedded in paraffin. Tissue sections were cut to 4km thickness and stained with Hematoxylin-Eosin. Histopathologically, most of the lesions, in intensive system, were mainly consisted of edema and hyperemia. However, epithelial hypertrophy, hyperplasia and telangiectasia were also seen. In extensive system, the lesions were more severe and were mainly consisted of edema, hyperemia, acute hemorrhage, necrosis and fibrosis. From the 384 samples of each culture system, 124 cases were injured in the intensive culture system and the whole of 384 cases were injured in the extensive culture system.