Diel vertical migration (DVM) is one of the major biological rhythms observed among zooplankton. In tropical environments (TrE), zooplankton is believed to exhibit prominent DVM. Chaetognath, a major vertical migrator among zooplankton in the global ocean, was studied from the Bay of Bengal, an important zone in TrE of Indian Ocean. Here a novel method (abundance-weighted tolerance index) was introduced which was successful in predicting the species, capable of performing DVM. The vertical profiles of physico-chemical variables exhibited a wide variation in upper 1000 m and only two species of the total twenty-five species exhibited significant DVM which opposed the general concept of DVM in TrE. The pronounced variations in physico-chemical variables acted as invisible barriers for zooplankton to perform DVM. The observed restricted DVM will have significant impact on the marine ecological processes including biological pump in the system.