Scholarly record

RESEARCH ON BACTERIAL DISEASE IN SILVER CARP (Hypophthalmichthys molitrix Val.), FARMED IN PONDS

Cecilia Bucur

Abstract

In the present study are presented the causes and consequences of a bacterial disease signaled to the silver carp farmed in polyculture with Cyprinids and other fish species in ponds. In the spring of 2017, the presence of a bacterial disease of the species Hypophthalmichthys molitrix cultured within the Fish Culture Research and Development Station Nucet, Romania, was first reported. The illness caused the weakening of the fish body (Fulton's coefficient = 1,6 compared to 1,9 for healthy fish) and a slight anemia with the appearance of haemorrhagic lesions on the body, without significant mortality. The causal agents was isolated and identified on culture and bacterioscopic media by Gram staining. The bacteria Aeromonas hydrophila and Shewanella putrefaciens have been identified. Only Aeromonas hydrophila has been reported in the kidney, which has been tested for susceptibility to various drugs. In fish without ascites, histological changes were identified in the cutaneous lesion. In the internal organs: liver, spleen and kidney, there were no significant changes. In fish with ascites, liver and kidney show severe histological changes. Leukocyte formula, hemoglobin and erythrocyte counts have been determined in clinically healthy fish but also in those affected. The mean hemoglobin was 8.2 g / dl in diseased fish and the number of erythrocytes was 1.326 mil. / mm3, compared with 10.8 g / dl and 1,830 mil./mm3 in healthy fish. Investigations were complemented by the identification of ecto- and endoparasites. We believe that the disease was based on cumulative factors: harvest handling and transport stress and median factors below optimum in the 2016 growth season.

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