Effects of metribuzin on rainbow trout (Oncorhynchus mykiss)

The aim of this study was to assess the effect of metribuzin on rainbow trout (Oncorhynchus mykiss). An experimental group of fish was exposed to Sencor 70 WG pesticide product (active substance 70% of metribuzin). The acute semistatical toxicity test lasting 96 h was performed on rainbow trout juveniles. The 96hLC50 value of Sencor 70 WG was 89.3 mg/l. An examination of the haematological and biochemical profile and histopathological tissue examinations were performed on one- to two-year-old rainbow trout after 96 h of exposure to Sencor WG 70 in a concentration of 89.3 mg/l. The experimental group showed significantly lower values (P < 0.01) of plasma total proteins, triacylglycerols, aspartate aminotransferase, ammonia, calcium, lactate, alkaline phosphatase, erythrocyte count, haematocrit and significantly higher (P < 0.01) values of erythrocyte haemoglobin compared to the control group. A significant decrease (P < 0.01) in both the relative and absolute lymphocyte count and a significant increase (P < 0.01) in both the relative and absolute count of neutrophile granulocytes were also recorded in the experimental group. The histopathological examination revealed mild proliferation of goblet cells of the respiratory epithelium of secondary gill lamellae and hyaline degeneration of epithelial cells of the renal tubules of the caudal kidney. This alteration of kidney resulted in hypoproteinaemia, followed by the formation of transudate in the body cavity. The metribuzin-based Sencor WG 70 pesticide product was classified among substances harmful to fish.