In the case of TFS, it is known that they reduce BG biomass but the productivity of the system is improved for LMB.
The studies are very inconsistent on this issue with studies going different directions. Some find increased BG biomass due to less predation on early age BG ....
I can see that but it would be great to understand what conditions are responsible for the differences. I would suspect that when BG biomass is below carrying capacity due to an overweight LMB forage-limited biomass that BG survival is increased. In that case, BG would benefit because LMB eat the TFS preferentially and the BG use of lower trophic levels was underutilized.
On the other hand, when BG are near carrying capacity, TFS compromise the BG food chain by competing with the creatures that BG eat. In that case, BG would have less food available and their biomass and RW suffer as a consequence.
I too suspect that TFS and TP interactions are similar. Even so, in either case, LMB benefit but for BG ... it depends. I would be very suspicious of any study which might claim that the ultimate BG carrying capacity would be increased by the addition of TFS (or TP for that matter). For anyone with an emphasis on BG, these species are very likely problematic.
Most misunderstand what "carrying capacity" is. That number changes constantly and from season to season. In very general terms, carrying capacity is not for an individual species, but for all biomass in relation to how much total food and O2 is available and how much waste (ammonia, nitrites and nitrates) bacteria and plants can remove. Since Tilapia do not eat foods most any other aquatic creature eats, Tilapia will increase the carrying capacity, often doubling it or more. By eating the "wasted nutrients" (FA and detritus) in a pond, and then becoming prey, most every other species will grow more, larger fish. Tilapia often increase DO levels in a BOW while reducing biomass consuming O2, yet also reduce FA which produces O2
...yet in the end, there will still be a net gain in O2.
As for the study saying Tilapia were not often found in "larger LMB", I'd be interested in knowing what time of year the LMB were looked at...I doubt it was when Tilapia were lethargic. From my many observations in clear waters, Tilapia over 4" inches, in waters above 70 degrees, are extremely difficult for bass to catch. In mid summers, I have watched bass totally ignore schools of edible size Tilapia...I theorize that the LMB learn they are too much work to even try eating them. Once Tilapia become lethargic, I'd lay odds on all sizes of LMB being bloated with Tilapia after a lavage....
With Tilapia present, Tilapia under roughly 4 inches become the primary forage species. This can greatly reduce BG being preyed upon while Tilapia are thriving. Once water temps drop, and Tilapia are decimated by being gorged upon, there will be greater numbers of BG, and more size classes due to the "extra" forage the Tilapia were for the yoy BG.
I can't even begin to estimate how many pounds of forage Tilapia can produce in a season, especially since most are consumed before reaching 4". It may be worth noting that Mozambique and Blue Tilapia (and their hybrids) will reproduce about every 3 weeks, and can go from egg to 1.5 pounds in 6-9 months...Tilapia also grow an inch or more a week till reaching about 6", so they feed a wide size class of predators.
I do recall a polyculture food fish study with catfish and "tilapia" (species not identified)....100 pounds of Tilapia were put into a catfish pond containing 1000 pounds of catfish. No feeding or aeration was done and at harvest 4 months later, there was 1260 pounds of catfish with 20% mortality by numbers and over 1000 pounds of tilapia.
