One observation I have seen with BCP and especially with WAE is when you have a massive hatch, very few survive because of numerous variables-one being competition for food.
With low survival, as things begin to regain a balance, the number of (low) survivors begin to grow very rapidly. By yr 2 these survivors are very healthy and in above average condition come spawning time. In my latitude this shows up about every 4th year and I believe in some cases it's just a cycle they go through when conditions are not absolutely favorable.
jpsdad is right in that it's a thought provoking question but for the purpose of removing numbers I think I would blast them pre-spawn/spawn, and "maybe" the predators will leave less to grow-that do hatch.
By doing this you are leaving more at the bottom of the food chain which IMO is most important for more uniform balance.
My 2 cents..
