Further, anyone can fork a coin at any time; there could be dozens a year. Am I supposed to keep track of every single fork of every coin I hold? Also what if

Further, anyone can fork a coin at any time; there could be dozens a year. Am I supposed to keep track of every single fork of every coin I hold? Also what if I haven't imported my private key into the forked coin's wallet? Do I have to report the income right away or only until after I've gained control of the coins?