Bill, apprx how many offspring will a mature 6" yp have in the spring in a lake filled with sticks and debris for spawning on?
Let's make some guesses for this answer. If our 80 ac lake has stunted 200,000 YP that is 2500 YP/acre. That IMO is a reasonable estimate for a one specie stunted population. In my 0.7 ac pond in 2013 I removed 1200 GSF and in 2014 I removed 3231 GSF (all 1"-6").
A stunted 6" female YP could have 18000 eggs whereas a regular 6" female may have 20000 eggs. Lets assume 70% of the 18000eggs of our stunted female actually hatch = 12600 fry/female (18000x0.70). 200,000 stunted YP with half or 100,000 as females = 1,260,000,000 (1.26trillion) total yolk fry produced/hatched or 15.75million fry/acre. Fry disappear quickly depending on predation, but most often most loss is due to lack of a proper food source for the swim up fry. In a clear water lake with lower planktonic rotifer populations (1st fry foods), easily 80% to 90% of the hatchling fry can starve without enough tiny planktonic food. This leaves 252 to 126 million surviving fry in 80 ac.
Let's assume each of the hungry stunted YP eats an average of 20 fry per day which is 4million total fry loss per day so after 40 days our 252 million surviving fry has now shrunk to 92 million 'fry' and the 126 million fry only lasted 31.5days (now a food shortage, thus stunting).
Probably only around 80%-88% of the fry starve to death leaving about hundred thousand surviving small 1"-2" YP fingerlings to replace natural mortality that occurs annually in the 80 ac lake and most all lakes, even ponds. Natural fish mortality is often estimated to be around 25%-35% so around 50,000 to 70,000 of our 200,000 mature stunted YP die of various causes of natural mortality each year and are replaced by the annual recruitment.
It is thought that this natural mortality of 25%-30% of the mature fish will die each year in your pond weather you harvest them or not. When there is no harvest then crowding and stunting occurs resulting in overall more smaller fish dying instead of fewer larger fish dying. The 25%-30% estimate is possibly more of a weight calculation than a number amount.
