Well if you are catching tilapia, green sunfish, bullheads, carps and plenty of mosquitofish suggests that this area holds hardy, tolerant and undesireable fish which means the habitat isn't good for sensitive, rare and desireable fish.
A nuisance fish means a fish that is too small or unacceptable or bothersome to the anglers. Green sunfish, bullheads and carps fit this.
A professional angler doesn't like those fish, it's true. But you can eat a larger bullhead, specific species of carp in low quantities do help with vegetation control (specifically hydrilla here in florida) and I'm sorry, but kids and myself and many like just going out and catching some panfish because they are so readily available in nearly every lake here in central florida. The carp here are typically grass carp and are released and controlled by fish and wildlife. They release only females in certain quantities each year.
Maybe I didn't word that correctly, but I did separate them between paragraphs. The lake I'm talking about doesn't have tilapia, that was a reference to the original post towards the red tailed tilapia.
What to you is a sensitive rare and desirable fish? The shiner population is next to ridiculous, you can get your day's worth of shiners in 15 minutes with 2 slices of bread and a size 16 hook. Because every time I'm out on this spring fed 442 acre lake (with the species listed) I get atleast 5-10 fish in 2-3 hours. Depending on bait of course determines LMB, SMB, and pickerel. Quality depends on the day but the smallest outing always produces a 4-6 lb LMB, 2-4 lb SMB or 18-24 inch chain pickerel. Winter crappie is pretty good too if you can find them. Being spring fed means it has a small current and the crappie move a lot. But I've pulled a boat limit (for florida) in 5 hours with the smallest being about 12 inches and 1 lb. Largest being over 2 lbs (IIRC 2 lbs 4 ounces).