Here's a post from Bob from awhile back. He is much more eloquent than I, and covers many species.
Geez, guys. I'm not sure I completely understand the question. Is the question how many fish can be raised in a single species put and take pond situation? Or, is the question which combinations of these different fish work well together and how many of each can you grow? Or, is the question how well will all these species of fish work in one pond? And then, recruitment comes only from restocking, based on what we might assume 'natural' mortality to be, basing that concept on old age?
To understand how to answer all of these questions, we first need to understand a pond's ability to produce, then sustain a population of fish, artificially propped up with pelleted fish food.
Here's what I have learned through experience...watching, thinking, building, draining, measuring and weighing lots and lots of fish. Oh yeah, and reading, too.
One variable will be age. Different fish have different age limits, based on geography, habitat and food chain. For example, a native northern strain largemouth bass in Texas can live to 8 years of age, sometimes 10, but one fish in particular, in Illinois, as I recall, was documented to live to 22. For discussion, let's assume each fish has 'x' number of heartbeats, then passes on to the big skillet in the sky. Relatively speaking, the number of heartbeats is an environmental consequence, since fish are cold blooded (like a handful of our distinguished colleagues on this website)
So, my take on the individual fish are as follows...
LMB-Largemouth bass. Two key thoughts here. LMB are instinctively predatory, so a pond's carrying capacity is directly related to the amount of natural food available. Typically, a one acre pond can support 50-75 pounds of LMB, with strong support from bluegill. The second thought is concerning LMB conditioned to feed. I know the fish farmer who started this trend, and they claim 4-5,000 pounds per acre. But, they can exchange water, feed the fish religiously, and use the most expensive feed on the market. But, for John Q. Pondmeister, 300-400 pounds per acre is probably more reasonable. The limiting factor is how complete the feed is. Keep in mind bass on feed are typically obese, and their lifespans are shorter. How many fish to stock? Depends how big you want them to become. In the first example, stock 50 fingerlings, or as few as 20 advanced intermediate size fish to begin. For the second, stock as many as 100-200 fish per acre. Expect pellet trained bass to convert about 3 to 1. Bass which eat live food exclusively convert around 10-1.
SMB-Smallmouth bass. SMB can be maintained at similar rates as largemouth bass, when stocked as the primary predator. Standing crops are similar to LMB. Habitat issues are considerably different for SMB compared to LMB and have a direct impact on the pond's ability to grow and sustain the population. As goes the pond, so goes SMB. Not as much for LMB. If feed trained, expect 3 to 1, maybe a bit less.
HSB-Hybrid Striped Bass. HSB are 'patrol' type eaters, opting to stay on the move, in deeper, open water. But, an average pond owner can expect to grow as much as 400-600 pounds of HSB in a one acre pond, all things being even for the 'right' habitat. Numbers of fish? Again, depends on the size. I would go with 100-200 in a single species stocking, dependant of fish food. An old hybrid striper in the south is 8-10 years. I honestly don't know how long they will live. Expect 2 or 3 to 1 as feed conversion rates.
CC-Channel catfish. These are the easy guys. We can easily stock as many as 100 in a one acre pond, not feed them, and they will thrive and grow to 2-4 pounds each. But, feed them, and you can stock up to 1,000 and expect them to make it to one pound apiece, when productivity is maxed. When a pond pushes to 1,000 pounds of channel cats, expect nature to push back. A 15 year old channel cat, in the south, is old. They convert fish food near 2 to 1.
Sterile Grass Carp. These fish are less known, because no one raises them for a put and take fish. They are used to control excess vegetation. But, they convert wet weight of food somewhere in the range of 40 to 1. I've watched grass carp go from one to seven pounds in a Texas lake from November to July. But, how many can a pond support? These fish are quite different. They eat methodically, all day long, and gain weight fast. But, once the food supply goes away, they drop that weight almost as fast. I have seen grass carp grow from 35 pounds to 12 in less than six months. So, a put and take pond of grass carp could literally see 20 fish swell to 700-800 pounds totally, then shrink and maintain at 300. Again, feeding alters the equation, but not much with grass carp, unless you plan to add lots of grass clippings, hay or bibb lettuce. These creatures normally live to 13-14 years in warmer climates.
Walleye-these top line predator fish fight to make a life. They eat other fish, including each other, often, without conscience. If a one acre pond can support 30-50 adult walleye, give yourself a big pat on the back. But, to get them as big as six or seven pounds, budget 8-10 years and lots of gallons of northern fathead minnows. While walleye are predators, their habits are such that fish as bluegill aren't efficient forage fish. Walleye would rather live deep, in structure. Bluegill choose shallow, in dense cover. Walleye convert live food at the rate of 8-12 pounds of fish to one pound of walleye.
HBG-Hybrid Bluegill. Lots of debate about this fish. As a target, singular species, a one acre pond can easily support 500-600 pounds. If they weigh an average of half a pound, stock 1,000-1,200. Want bigger? Stock fewer. Pushing the limit? A pond could grow as many as 1,000 pounds of HSB, but water quality issues would quickly follow. These guys convert fish food at less than 2 to 1. They live as long as 6-8 years.
Now, let's shift gears. Combining these fish completely changes the equations. Think about how each species lives, what they eat, their behavior patterns, habitat requirements and you will see what I mean. Alone, each fish might thrive in a one acre pond. But, put them together, and it's like the Pittsburgh Steelers lining up against the Nebraska Cornhuskers as they tease your favorite high school football team. In the meantime, HSB pirates are raiding the fridge in the middle of the pond, while LMB fight for space with walleye, who have an advantage over smallmouth bass, while spinach eating Popeye-sailor man grass carp are vegging out. Over there, in shallow water, laughing and munching, the HBG dart in and out, eating while trying not to be eaten. Then, spread an even helping of "productivity" around, and soon, you see fewer fish of each type as they thrive, while the other decline due to high competition, room rent and a run on the grocery stores.
Throw in one other factoid. Different individuals within each species exhibit different behavior. Some are aggressive, some are passive. Some grow fast, some grow slowly, just like all other creatures.
Here's the bottom line, from my beady little brain. A one acre pond, fed moderate amounts of fish food, will safely sustain 600-800 pounds of game fish. We can pick the combinations, but Mother Nature will choose the success, based on habitat, size distribution, growth rates, aggressiveness and luck of the predatory draw. (If a fish is eaten, is it our fault?)
Regarding the restocking question, the only way to know is to figure it out by regular monitoring of individual fish and their body condition. If regular samples of fish determine the little gems are overweight, the pond can support more. Stock a few. But, if the little toots are bit on the runway model side of size, there are too many, or not quite enough little food nuggets.
Now, what was the question?
