To determine the taxonomic status, characteristics, and histopathology of nematodes infecting the intraperitoneal tissues and organs of Bleeker, PCR analysis were used to evaluate 18S rDNA and ITS rDNA sequences and microscopic observations were used to evaluate nematode morphology and histopathology. Nematodes were identified as the fourth-stage larvae of and their ITS rDNA sequences were confirmed. Six spinous papilla and six papillary papilla were identified in the cephalic extremity and caudal plaques in the posterior of . In addition, data were supplemented, and new characteristics of morphological structures, including lateral plaques with grooves, were identified. Their body muscles were of the polymyarian type according to the number of muscle cells and their characteristics at one end of the body, which stretched into the coelom. The esophagus consisted of a dorsal gland, ventral glands, and a three-radiate esophageal lumen. The intestine was more cell type according to the number of monolayer columnar epithelial cells in the intestine. The outer layers of the ovary, oviduct, testis, and spermaduct were composed of connective tissue mainly with fibrocytes. Histopathological observations revealed that some nematodes infected the liver, mesentery, and spleen, with the formation of cysts in the abdominal cavity of fish. The main inflammatory responses were the formation of cysts, which were mainly composed of fibrocytes, blood vessels, and many infiltrated eosinophilic leukocytes. The cyst underwent formation, wall thickening, enlargement, cell wall necrosis, and rupture in the late stage. Severely infected livers appeared congested, with cell necrosis and hemosiderosis. The spleen presented ischemia and hemosiderosis. Secretory granules of pancreatic cells in the mesentery were increased. Thus, infection with the fourth-stage larvae of induces different degrees of histopathological changes in the internal organs of host fish.