The spawn success is 75% environmental ( temp , silt , oxygen , sun , wind , floods , waves , GOD stuff! ) that is why you can have about the same amount of breeder females from year to year and have some fantastic hatches or some duds!! It is really very simple. Much like our winter / summer. Last summer in Michigan ( mid July ) 6 nights with lows in the 40's , and this winter cold as Heck. 2 years ago and for the last decade all boo hoo a our global warming , and now they call it climate change because it is cold as heck for 4 months and that about covers everything HUH?? Plain and simple DNR will adjust bag limits as needed. We have never had such good management of our resources!!! And it will provide for years yo come , as long as we keep supporting it!!