Don't think you alone can affect the size rate significantly unless you are hitting it really really hard. The fish can just breed a ton of new spawn each year to replace the drop in the bucket you might make. This depends on size of the body of water greatly. If it is over 50 acres or so i don't believe any single person could affect it. Smaller lakes can be managed but that gets tricky if there are others fishing it and not following your same standards.
My home town has two reservoirs now....... the 'old res' sounds very similar to what you have going on. It can't be more than 15 acres in size and only 8'-10' at the deeper end. I went out tonight and have no clue how many 6" crappie i caught in the hour and half i was there. Back to back cast most of the time and not long casts at all as the fish are SHALLOW right now. Would even venture to guess as high as 40 in that time since they all just got un-hooked and tossed back.
On this reservoir, there was a big fish kill (man made as result from weed suppression) a few years back. Its result was the current lake condition except there are a few HUGE crappie that did survive the kill. I catch those giants less and less often now. When the smallish crappie hit 8"-9" nearly every one will go in my bucket when i do fish it.
That said, i still only keep what my family eats. My freezer is bare of fish at the moment because i suck at winter fishing and mother nature did not want to co-operate again this year and let me get out on the ice much. I do give away a few bags of fillets to friends and neighbors thru the year, but not much.
If they are white crappie they are very prolific spawners. Blacks a much better choice for ponds and smaller lakes.
