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