There should be NO oxygen depletion due to applying rotenone. Rotenone does not remove the oxygen(DO) from the water. That is a misconception. Rotenone is absorbed through gills and when in the blood interrupts oxygen transfer in the animals tissues / cellular structures.
Rotenone inhibits cellular respiration and the ability to use dissolved oxygen. In effect, the fish suffocate. Fish exposed to lethal rotenone concentrations move to the surface and gasp for oxygen AS IF the water was oxygen-depleted. However, rotenone does not reduce the amount of oxygen dissolved in the pond water.
MORE DETAILS – Rotenone interrupts aerobic cellular respiration by blocking electron transport in the cellular mitochondria through the inhibition of the enzyme NADH ubiquitone reductase, which prevents the availability of oxygen for cellular respiration.