I was trolling shiners around the lake and a 50 pound tarpon eat my bait and broke me off after jumping twice. Has anyone ever heard of this before? :-?

Yes, tarpon are notorious for jumping and throwing the bait.  

How did a tarpon get into lake panasoffkee? I have fished serveral times there and have all seen bass and crappie caught...

Are you sure it wasn't a CARP?  

http://images.google.com/images?rlz=1C1CHMG_en___US303&sourceid=chrome&q=grass%20carp&um=1&ie=UTF-8&sa=N&hl=en&tab=wi

various saltwater species, including tarpon will migrate into fresh water and adapt, they could have been released by soemone, or even a bird was carrying its dinner and droped it in there, whatever the case,it does happen. in the retention canals around my town we have tarpon, and there have been various reports of people catching snook as far in as lake okeechobee. it jsut sorta happens.

That would have been fun as  

I was trolling shiners around the lake and a 50 pound tarpon eat my bait and broke me off after jumping twice. Has anyone ever heard of this before?

How do you know it was 50# if you got cut off?

They have razor sharp gill plates, when they roll they cut your leader, same with snook.

Both tarpon and snook congregate at spillways when the gates are open and freshwater baitfish are carried out by the current. Sometimes they swim thru the gates and enter the canal system and become trapped, gates are closed in dry season. They survive freshwater just fine but cannot reproduce.

Tarpon jump?........I should say so. They have a bone hard jaw and hooksets are difficult( with bait use a circle hook), usually 2 or 3 jumps and they're gone, need a little luck to land them.

This has been an excellent year for tarpon, have caught many.

I caught a 25in. snook in a 10 or so acre pure freshwater pond around here. I see other people catch them all the time, snook that is, not tarpon.

Snook and Tarpon adapt to freshwater.  It is not uncommon to catch or see them swimming around with the bass.  I've seen 1 snook caught on Lake Okeechobee during a tournament years ago.  It wasn't the typical pretty snook you find in the surf but it was still a snook.