The histopathological changes in various organs of Cynoglossus semilaevis Günther infected with red abdominal shell disease were observed by dissection and HE staining. In the ill C. semilaevis, the body surface was congestive and bleeding;the skin in the blind side ulcerated with extravasated blood; the gill filaments ulcerated with a lot of mucus; the liver, pancreas and spleen were swelling and bleeding with extravasated blood; the small intestine was congestive and bleeding. Degeneration and necrosis, and submucosal bleeding occurred in the skin of C. semilaevis infected with red abdominal shell disease. There was red blood cell infiltration and deposition in the space among muscle fibers. Epithelial degeneration and necrosis occurred in the parotid gland. The efferent branchial artery was congestive. The myocardial fibers had a loose structure, and a large area of fracture appeared. The liver cells were swelling with degeneration and necrosis and concentrated nucleus. A large area of the renal interstitial was broken down and necrotic. The submucosa of the small intestine had necrosis and hemorrhage.
Tilapia has wide-range tolerance to salinity, and most Tilapia species can survive in both fresh water and seawater. In this study, the survival rates, absolute growth rates and instantaneous growth rates of Tilapia nilotica and Tilapia mossambica in waters with four different salinities（0‰, 10‰, 20‰, 30‰） were investigated.The results showed that the growth of T. mossambica was trended to be increased with the increased salinity, and it is suitable to be farmed in seawater; however, the growth of T. nilotica was trended to be decreased with the increased salinity, and it is suitable to be farmed in fresh water.
