As others have said, it depends on the species and the water fished.

In my area:

Small stream browns: 16"
Big River Browns (Beaverkill, Delaware): 21"
Small stream brookies: 11", maybe 13" on some waters.
Lake-run Browns from Finger Lakes: 10 lbs
Lake-run LL Salmon: 6 lbs

These are the sizes that I consider to be "big" but not necessarily trophies. Just good-sized fish that are caught periodically between smaller fish.

[This message has been edited by Spud (edited 07 April 2006).]