Abstract:The current development of Xinjiang indigenous fish via large-scale farming has been listed for the positioning and development of aquaculture in Xinjiang. Perca fluviatilis Linnaeus is an indigenous fish and peculiar to the Ergis River in Xinjiang. P. fluviatilis is a cold-water fish, but very few studies have investigated cold-water fish diseases, including bacterial disease. Presently, artificial breeding of perch is being initiated. However, there have been few analyses of disease in perch. In 2016, a large number of perch in the Wujiaqu Fisheries Extension Station died suddenly. Diseased fish exhibited anal swelling, abdominal swelling, surface scale cast-off, rotten tail, and rotten gill symptoms. The dominant bacterial strain was isolated from the fish liver and intestines. After culturing for 24 h at 20℃, ZL1 formed neat edges with a slight uplift in the middle, a smooth surface, a light-yellow color, a special aromatic odor, and bacterial colonies 1.5~2 mm in size. It formed a clear β-hemolysis circle on blood agar. ZL3 and ZL5 formed a round, slightly uplifted, smooth, moist, off-white, translucent, colony of 0.5~1 mm in size, but did not form a hemolysis circle on blood agar. The isolated bacteria were cultured, the bacterial species were identified, and drug susceptibility and pathogenicity tests were performed. Pathogenicity tests and morphological observation showed that the isolates had obvious pathogenicity. Gram staining, physiological and biochemical characteristics, analysis of 16S rRNA gene sequences, and phylogenetic tree development identified ZL1 as Aeromomas sobria, and ZL3 and ZL5 as Edwardisella tarda. Drug sensitivity test showed that ZL1 was highly sensitive to gentamycin, minocycline, and ceftazidime, and resistant to streptomycin, penicillin, and clarithromycin. ZL3 and ZL5 were highly sensitive to levofloxacin, streptomycin, and enrofloxacin, and resistant to gentamicin, ampicillin, penicillin, and sulfamethoxazole.
