One of two things;
Bass as in Guitar. Otherwise it would mean Super Fish.
The flaps on a fish are called fins, which help the fish to maintain balance, steer, and move through water. There are different types of fins on a fish, such as dorsal fins, pectoral fins, pelvic fins, anal fins, and caudal fins.
I guess you mean "Anal fin". If so, the answer is "yes fish do have an anal fin."
You can find bass on the Catherby shore or the fishing guild. Please note it is a members only fish.
They are on the Ventral side, but you probably mean the Pelvic fins and possibly anal fin, depending on the fish species These links provided below may help you :)
To swim..? If you mean the fin on top of their bodies then it helps stabilize them.
It means that something ripped their tails or fins, most likely the teeth of another fish.
if you mean bass its a big fish tat lives in fresh water mainly rivers i think
Although I'm not sure what you mean by "deep" body, Betta fish, or Siamese Fighting Fish, or Rumble Fish (if you're S.E. Hinton) are thin, brightly-colored (domestically bred males tend to be more colorful), and have long, wavy fins.
Sunfish,I assume you mean rock bass ,pumpkinseed,bluegill,ect,more than likely protect themselves,as a first measure,by hiding and getting out of the way of bigger fish fast.Second, it seems to me all sunfish have pretty sharp spines the stick out of their dorsal fins,and there always pointing back,away from the head.This would seem to me that bigger fish that try to chase the sunfish,to swallow it from behind,get stuck in the mouth with those sharp spines.I once caught a nice calico (aka rock bass) on a minnow jig,and I stuck myself pretty good on back fin while taking it off the hook,it drew blood!
Bettas are slow retiring fish. They do not move around much normally. Silvery coloured "pectoral fins" are quite common.
gills for breathing and fins for swimming if thats wat u mean.