Improved survival of rohu, Labeo rohita (Hamilton-Buchanan) and silver carp, Hypophthalmichthys molitrix (Valenciennes) fingerlings using low-dose quinaldine and benzocaine during transport

The effects of fingerlings immersion in low-dose benzocaine (15 and 30 mg L-1, silver carp and rohu) and quinaldine (100 mu L L-1 silver crap and 250 mu L L-1 rohu) for 1, 3 and 6 h on stress responses and survival of rohu, Labeo rohita and silver carp, Hypophthalmichthys molitrix fingerlings were evaluated in a transport simulation experiment. Both quinaldine and benzocaine showed low mortalities (0-2%). The total mortality in control (with no anaesthesia) was 30% for rohu and 14% for silver carp. Quinaldine and benzocaine-treated fingerlings had significantly higher plasma chloride levels than the control in both species. Benzocaine, quinaldine, as well as the control, had an initial elevation of plasma cortisol levels. Benzocaine lost its effectiveness after 3 h exposure while quinaldine persisted throughout the 6 h experimental period. Both sedatives reduced bacterial build-up compared with the control. No post-exposure mortality was observed for any of the transport methods assessed 48 h after the treatment. This study suggests that the use of low-dose benzocaine or quinaldine during transport has positive effect on the survival and health of rohu and silver carp fingerlings.