Generally a forage species and predator species are considered most compatible when each has a somewhat different niche and the adults feed on mostly different rather than similar food items. Adults feeding on different food levels allows the pond to produce a higher biomass of fish.
Bill this is an area that has long interested me particularly as it applies to favoring the biomass of a particular species. When a predator like LMB or SMB are considered, whether they can achieve a greater standing weight when combined with prey fish depends in large part on what the combination is. So typically, alone LMB might range between 50 and 120 lbs/acre whilst SMB between 75 and 180 lbs. One would think that introducing fish prey would sustainably and significantly increase the standing weight of LMB and/or SMB. But if this prey fish is BG, the LMB standing weight is not improved whilst the SMB standing weight significantly diminished. So a prey fish like BG does not provide much (if any) additional food to support a biomass of LMB and it actually removes food supporting a biomass of SMB.
I have to admit, when I first learned this about the LMB/BG combination, my intuition rebelled against it. However, when we think about interspecies competition ... the complex picture of species interaction begins to take shape. The difference between an LMB pond with BG and without, even though the biomass of LMB isn't significantly altered, is a remarkable difference. Without BG, there are many LMB of small sizes whilst with BG there are fewer LMB where some attain much larger ultimate weight.
The solo predator scenario is an interesting scenario in part because a large proportion of the biomass, though distributed through many fish, are of harvestable size. For example, subsequent generations (offspring of original stocking) of the solo scenario of LMB tend to grow faster in the first two years of life than the subsequent generations do in the presence of BG. This slowing effect on LMB growth in their early life is due, of course, to interspecies competition. BG YOY outgrow the LMB fry and fingerling gapes and eat many of the same foods. What this means from the perspective of the solo scenario is that subsequent generations have the potential to attain a harvestable size in their first year of life. It is interesting that predators can be cropped at annual weights/acre that are comparable to sustainable (supporting balance) combined crops in predator/prey combinations.
On the other hand, we can think of other combinations of prey that might support a greater standing weight of predators than a hardy prey fish like the BG. On this tack, I haven't discovered research that satisfied me that they were seeking data under sustained cropping of the predator. Even so, some the LMB standing weights achieved are noteworthy. For example, with GSH and FHM as prey, standing weights approaching 400 lbs/acre were achieved in 1.5 years. This led to the extirpation of the FHM of course. Swingle achieved 170 lbs/acre with Gams in 1 years, again this led to the extirpation of the Gams. To be sure, these high standing weights for predators are not likely sustainable under any scenario but it would seem they suggest some prey, when not competitive, may allow for increased carrying and production of predators. Prey that can persist without extirpation, that remain small and vulnerable to predators throughout life, have high reproduction rates, produce large crops of offspring relative to their standing weight, exploit lower trophic levels, and have short spans of life that turnover the population are what I would consider "ideal" for this purpose. To large degree, the persistence of populations is the key to providing forage that expands production on a sustainable basis. I think part of this picture are the vigor of the prey. But in terms of management, the cropping of the predators might help give seasonal abundance to the prey and seasonal reduction of predation allowing more marginal prey to be viable. Habitat can play, as esshup mentioned, a very important role as well.
I think SMB are particularly interesting because they are less dependent on fish prey early in their life. The delay of full on piscivory, (it might possibly be argued that they are never truly full on piscivores), may render some of the smaller minnow species that are unacceptable candidates for LMB viable for SMB on a sustainable basis.
