Would like to increase bass size while maintaining large crappie ................... asking too much ??
I don't think its too much ... provided ... your expectations of increasing bass size are modest.
Bill made some excellent points:
The larger the bass become the smaller the average size of crappie will be. The two different populations are tied together as a small bass / large crappie balance in several ways. Deleting or removing enough LMB in a 35 acre small lake to start to see development of some larger bass will be a really big challenge.
It would be good to understand the populations of LMB and Crappie in terms of biomass. This would give you the knowledge you need in order to understand the limit of what should be harvested of each species to maintain the fishery near its current balance. When I read your goal what I really see is that the maintaining crappie size is the primary goal. This is understandable because good crappie fisheries in impoundment like yours aren't really common. Your organization has an exceptional one and I think this isn't only due to the presence of many LMB but also due to absence of BG.
In support of Bill's first point, it will be a challenge to see LMB of much larger size. If your goal were an increase of length by 50% then (assuming relative weights remain consistent) the biomass of individuals would increase by 3.6 fold ... with an improvement of 10 RW we are talking 4 fold or more. This essentially means that all other things being equal ... in a lake that supports the current biomass of LMB ... 75% of the LMB numbers must be eliminated to grow 50% in length. To be sure, to remove that many would allow the Crappie to recruit more than they presently do and this would limit Crappie ultimate growth violating your primary goal.
What would be a good practice is to harvest both species as a form of maintenance. Harvest LMB to mostly to improve condition of LMB... and harvest Crappie to offset increased recruitment cause by harvesting LMB and reduce intra-species competition. Now I say maintenance because the water is already a great crappie fishery and this is the primary goal. Keep in mind that growth follows an equation that depends of two variables ... mortality biomass and recruitment biomass. Subtract the recruitment from the mortality and what you have is a biomass that represents under utilized carrying capacity that can be gained by adult fish (not YOY recruits which we subtracted). For a lake at carrying capacity in terms of its fish biomass, there is no growth without mortality. Harvesting introduces mortality and makes room for individual growth. If you harvest 20% of the biomass (if all length categories equally benefit) then there will be an increase in length of 6%. So back to being modest about expectations, that is not even an inch for 12" fish. If RW improves it is even less increase in length. You will not be able to maintain the Crappie fishery and substantially improve the LMB. Just consider the LMB a harvestable means to the end of a remarkable Crappie fishery.
If something is done to change the current fishery balance, EVERY angler should start recording ALL sizes and numbers of every fish caught both released and harvested to provide a data baseline to yearly monitor the changes that are occurring in the balance and size structure of the two fishery populations.
I would like to suggest using lengths as quick efficient way to manage the metrics. Yes, it doesn't tell one the RW or the exact weight of the fish caught or removed ... but I can guarantee that in a situation like the OPs that everyone isn't going to individually weigh fish. Some may even resent having to buy a scale of sufficient quality to do it right. Using lengths is a surrogate method that can provide an effective metric for management in situations like this.
Probably the best way to keep track is a spreadsheet. I will add a spread sheet tonight that would work with multiple species and work with lengths.
