Embarrassed to ask but....

[greggbert]

Is it true that you can somehow get lamp oil from ice fishing or was I being trolled?

[Khan_Drichthyes]

You get the oil when you cook the fish.

[Jolan]

very, very small amounts.  Bigger the fish, the bigger the amount of oil.  

[Khan_Drichthyes]

Of course, using fish oil as an accelerant or as lamp fuel is a more fictional aspect added for gameplay purposes.  It will burn, but requires much higher temperatures than the lighter fluid and lamp oil (Most likely Kerosene).  But, just as the disclaimer points out, it's a game, so enjoy.