Well sort of anyway...

In FT you have 5 save game slots, Go to your FT directory any copy your savegame, you should have something like.. copy of "fishsavegame1.pts" Change the "1" to 5
When you now go into the game you can load your original game in the 5 savegame slot and play away, Excellent if you want to experiment but dont want to sell your fish.

If you feel more adventurous you can load the savegame into a hex editor and at the very bottom is the name of the game as you see it in the loadgame screen, rename this to diferentiate between the 2 games.

Excellent game LDW Best thing ive brought in ages :-)
( Waiting like BAIT for FT2 )