The best reason I can think of to add adult LMB is when they do not recruit sufficiently to replace themselves. Examples, Female only initial stockings or where culling has reduced the male populations sufficiently to inhibit successful recruitment of LMB. Water with high populations of forage in consumable sizes and with few adult male LMB would be candidates for supplementation of female LMB. The supplementation rate would depend on whether one wants to catch and release to end of life or to harvest a limited number of trophies annually. Ideally, one wants the population of adult LMB to be relatively stable over time where mortality equals recruitment. The benefit of annual recruitment of LMB is to spread the population across multiple year classes where each class can grow at satiation rates of growth. This also spreads the demand for optimal sized forage across a wider range of sizes.
Just a thought. When there is plenty of forage to go around and when LMB are sufficiently limited in number (making satiation weight increments), the conditions calling for the need of supplementation of recruits are more likely. Where annual weight increments are below potential, there is alternatively a need to cull the population of existing adults.
On the ratio of consumable forage to LMB. This is a number I would love to understand better. Particularly, how numerous do prey of various relative prey sizes have to be if the LMB are to feed at satiation. For each relative size of prey, there must be a limiting density ... below which ... LMB do not feed as much as their growth potential would require (due to insufficient numbers of successful pursuits). Predator reaction is a formal moniker for the metric.
Another perspective one could consider is the number of prey items they must consume annually. If an LMB requires 5 lbs of forage annually just to maintain itself (without growing), then how many prey items it needs depends on the size of prey it is consuming. If consuming prey that averages 1% of its body weight, it would take 500 prey items annually. If 5%, then it would take just 100. My guess is that it probably doesn't matter much which average size it consumes so long as either prey size is numerous enough to support the consumption of 5 times body weight annually. That is where the predator reaction function may be important. The reaction function is at least in part related to the frequency of encounters (population density) and success of pursuits (how difficult the prey is to consume when afforded an opportunity for pursuit). These two influencers of reaction are related to prey size, I think.
There was a paper I've posted here in the past on the relative sizes of consumed prey. The data was collected from numerous state DOWs over many years. For LMB, the median relative weight was about 0.92%, this suggests that to be maintained, these LMB were consuming ~ 540 prey items annually. Does a similar relationship exist in ponds?
