Simultaneous exposure to Formalin and Methylene blue water-bath as a common disinfectant on haematological and stress parameters of ornamental Pangasius catfish (Pangasius hypophthalmus)

Controlling ornamental fish disease has a key role in reducing treatment costs and improving growth and health status. Disinfectant solutions such as formalin (F) and methylene blue (MB) are some of the effective disinfectants in the aquaculture industry. In this study the effects of simultaneous exposure to F-MB on some haematological and plasma cortisol and glucose levels on ornamental catfish, Pangasius hypophthalmus were analyzed. 60 fish, average body weight 83.2±12.67 g, were randomly chosen and put in two groups, control and F-MB, in 6 separate glass tanks (each 10 fish). The fish in the F-MB groups were exposed to formalin, 5 ppm and methylene blue, 4 ppm for 72 hours. After exposing time, blood was taken from the caudal vein and some haematological parameters plus plasma glucose and cortisol levels were analyzed. The results showed that exposing fish to F-MB disinfectant could not cause any significant changes in preliminary and secondary haematological parameters in fish (P>0.05). Even though, fish in F-MB groups showed higher plasma levels of cortisol and glucose as tension indicators in comparison to the control fish (P<0.05). It could be concluded that although simultaneous exposure to F-MB could not affect haematological parameters of ornamental catfish, it had some negative effects on tension response and need to use under exact stewardship. Study on the other fish welfare parameters as well as exposure to other disinfectants can help us to select the best option under culture condition.