There is a very good article all about rotenone in the current isssue of Pond Boss magazine. Try to read it.
Rotenone will last several days to weeks depending on several variables such as water temp, suspended solids, water chemistry, and amount of plankton in the water. It will definately kill fish fry and at lower concentrations than it would have killed larger fish of the same species. I would also bet that rotenone will kill or stop development of fish eggs due to its affects on the oxygen carrying / diffusion capacity or transfer of oxygen to the blood. Developing fish fry have circulating blood; they just don't get the oxygen from gills at this stage.

Used PROPERLY and at the correct concentration it will kill all fish present.

aka Pond Doctor & Dr. Perca Read Pond Boss Magazine -
America's Journal of Pond Management