Physiology of Finfish and Shellfish (2+1)

Procedure

For the determination of dissolved oxygen, 50ml of water sample can be added with 1ml each MnSO₄ solution and alkaline iodide solution one after another. The precipitate is allowed to form.

At the time of titration the bottle with sample is unstoppered and 1ml H₂SO₄ is added to dissolve the ppt. a clear yellow solution appears.

This solution can be taken in conical flask and titrated against 0.01N Na₂S₂O₃ solution until pale hay-yet low colour appears. At this stage 3-4drops of 1% starch is added and the titration is continued till the disappearance of blue colour.

Experimental fish can be introduced into a 1.5l jar containing water. Before introducing the fish, its weight was taken and the amount of dissolved oxygen was also estimated using winkler’s titration method.After 30 minutes estimate the amount of dissolved oxygen in the water. The difference in oxygen levels between the samples gives the level of oxygen consumed by the fish in 30 minutes. After 30 minutes second sample was taken and the dissolved oxygen was estimated. The difference in the oxygen level between the samples give the quantum of oxygen consumed by the fish at fixed time interval. From the estimated values, the oxygen consumed by the fish is calculated as ml/l/kg/hr of fish.