Disrupted shoaling behavior, easy predation,
gulping air and swimming at the water surface
(surfacing phenomenon) were observed on the day of
exposure to sublethal concentrations of chlorpyrifos.
This situation further continued intensely throughout
the test periods, which is in accordance with the
observations made by Ural and Simsek (2006).
Gulping of air may help to avoid contact of toxic
medium and to ease respiratory stress. Surfacing
phenomenon i.e., significant preference of upper
layers in exposed groups may be due to elevated
demand for oxygen during the exposure periods
(Katja et al., 2005). Surfacing phenomenon and easy
predation continued even under recovery periods of
seven days in both the test concentrations. This
reflects the catastrophic impact posed by the toxicant.
Of all, phenomenon of easy predation is one of the
most serious damage caused by a pollutant on
sensitive species like fish, which ultimately decide the
survival of a species in a given ecosystem.