Investigation on Larvicidal Efficacy of Two Native Ornamental Murrels of Assam under Controlled Condition.

Background: It is widely reported that exotic larvicidal fishes like Gambusia and Poecilia have adverse impact on the native aquatic fauna. The present study highlights the efficacy of two colourful native murrels, primarily designated as ornamental fish, Channa bleheri and Channa stewartii as biocontrol agent of mosquito larvae. Methods: Live specimens of Channa bleheri and C. stewartii, collected from the wetlands of Tinsukia district of Upper Assam, were assessed for their larvivorous potential at individual and group levels during day and night by dividing the specimens into two size groups. After 12 hour and 24 hour starvation, the test specimens (mean size for small group 8.67-9.17 cm and that of large group 11.63-13.27 cm) were given known number of mosquito larvae and recorded the consumption rate. Result: The predation rate varied from 33.3±4.36 to 71.6±5.15/min for Channa bleheri and that of C. stewartii from 16.3±0.95 to 68.2±2.77/min. In both species, smaller sized specimens were better performers as predators. Predation rate at 12 and 24 hrs of starvation and between day and night proved that these native murrels are excellent predators of mosquito larvae. [ABSTRACT FROM AUTHOR]