Experimental design and sampling procedures
Artificial Argulus infection was carried by cohabitation method (Saurabh and Sahoo 2010). The fish were periodically observed for development of infestation. After 2 weeks of gestation, fishes were randomly selected and checked for the prevalence and intensity of parasites. Fish were chosen for the in vivo tests at the prevalence of moderately infested 15–20 Argulus/fish and randomly distributed in fibre-reinforced plastic tanks of 150-L capacity; in vivo bioassay was performed, and Argulus was treated off the host in an in vitro test for evaluation of antiparasitic activity of Azadirachtin against Argulus spp. The experiment was conducted in triplicate with complete randomized design.