Originally Posted by lunkertrout
Originally Posted by jpsdad
You don't harvest any LMB. Just the right amount of harvest of LMB will have a profound impact on growth LMB.

The LMB harvest point is well said and strikes at the heart of the issue. Points out the root cause of the topic I’ve been struggling with the most to understand.

Which is…For a 5ac pond, with white crappie present, what is the “right amount” of LMB to remove. Specifically, the right slot to protect, in the right quantity.

I would love to take out a few LMB, and I agree it would have a profound impact on their size. I just don’t want to miss on the side of too many and end up with a pond full of 4” crappie. I’ve been essentially paralyzed with that decision…what slot and how many to keep…so I landed with keep them all to ensure they consume every crappie spawn, which has kept them in check to this point. Would love to hear your perspective on what a “safe” LMB harvest strategy might look like in this scenario.

Probably the greatest threat to WCP over population is irregular recruitment and mortality of LMB. IOWs a super dominant year class of the LMB which will undergo high mortality after that abundant year class reaches old age. WCP can themselves impair recruitment of LMB. So I totally get your concerns about not wanting to take too many.

LMB have a great capacity to grow. For example, a 11" female LMB can grow by 1.6 lbs. But when a population is dominated by LMB less than 12", the growth is a minor fraction of that. Maybe as little as 1/6 of a pound (or even less) annually. Consuming optimal sized prey, the 11" LMB growing by 1.6 lbs consumes a little over 800 BG annually. The 11" growing by 1/6 lb/year consumes around 580. The difference is around 37% and this is probably the maximum mortality your population can undergo while still consuming the same number of prey fish. For example, if you have 100 LMB/acre averaging 0.60 lbs each, your population could have up 37 LMB mortality and still they would consume the same total number of prey. Assuming 10% natural mortality, harvesting 25 LMB per acre (this year) may not hinder predation.

The key to stability is stable recruitment and stable mortality. This leads to a stable population and population structure.

Anyways, you could probably take a total of 50 LMB from your 5 acre pond this year with no ill effects. 10/acre for 6 lbs/acre is not excessive IMO and you could see what effects this might have on both LMB growth and WCP recruitment before doing any more. Also, you could begin selecting 8" to 10" LMB each year to reserve as a core population. Say, for example, 10 LMB/acre-year. Do not keep those fish and after 5 years under 10% natural mortality you have a minimum of 40 LMB/acre protected under this arrangement. You could probably do this while keeping 10 LMB/acre year of unmarked fish. After 5 years, you could keep any marked LMB older than 5 years and any unmarked LMB larger than 10" and maintain a core adult population of 40 LMB/acre. That would probably be enough LMB to have a good balance with WCP and BG in your pond. What it would take to maintain this structure is recruitment of 10 8" to 10" LMB/acre annually. If you pond fails to produce these recruits, you supplement them. The benefit of stable recruitment is a minimum stable population over time.

It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers