Those black spots in the Rock bass are called, Black Spot. They are the encysted larvae of an intestinal parasite found in fish eating birds, like Blue Herons.
The bird poops in the water, the eggs in the poop hatch into swimming larvae, find and burrow into fish, and encapsulate themselves as black cysts. The birds eat the fish, the parasite emerges from the cysts, attaches to the birds gut, and grows into an adult parasitic worm, to complete the cycle.
Rock bass seem to be especially susceptible to Black Spot, but I have seen it in Bluegill, Perch, and bass too. I can handle eating fish with a few black spots, but get squeamish if there are more than 10 spots per filet.
White spot is even worse. A different species of worm that encapsulates as a much larger white grub. When you filet a fish with white grub, white worms actually come slithering out.
The are also safe to eat, but completely disgusting. Bon Appetit