Carrying capacity is the most limited standing weight the bow can support through the year.
It also apply to other wildlife, eg elk. The mountains can support many more elk in the summer than the wintering grounds can in the winter. The carrying capacity is determine by the wintering habitat.
In the case of a BOW and fish, the limit could be determined by many factors and only one these many factors is DO.
I stocked 42 HSB, 500 HBG, & 90 RES.
Neglecting reproduction of HBG and RES an estimate of the original stocker current standing weight can be made.
(1 - Mortality Ratio)* NumStocked* Current Avg Weight = Standing weight
If you have not harvested then it isn't unreasonable to assume less than 30% mortality. Let's be conservative and assume its 30%.
.70 * 42 * 1.6# = 47.04 lbs HSB
.70* 500*.5# = 175 lbs HBG
.70 * 90 * .5 = 31.5 lbs RES
Together what survives of your original stockers might easily weigh 253.5 lbs. That's 1014 lbs per acre and that doesn't include HBG and RES offspring.
This much I can tell you, it was feeding that got you to this standing weight. The standing weight of this mix of fish is well beyond the carrying capacity of the pond without feed inputs. In retrospect, I think the DO is consistent with the oxygen demands of this weight of fish and the latest state of the BOWs bloom.
QA, feel free to refuse this advice but I think your reluctance to harvest HBG until they reach 1 lb is a catch 22. I don't think they can reach 1 lb in weight unless you increase your feeding rate and I think if you do that you are risking them all to a fish kill. If it were CC, I would say go for a standing weight of 2000 lbs/acre but HSB and HBG might die if you don't stay right on top of it.
If you remove some of the HBG then they can continue to grow at the same rates of feeding, provided the HSB limit HBG recruits sufficiently. I would be willing to bet a great bottle of scotch that removing around 75 lbs of HBG would make a big difference in your DO immediately and since you already know that the BOW can support 175 lbs of HBG with your current feed rate, those that remain might make it to a 1 lb while maintaining your current feeding regimen.