Some eels however, remain in estuaries and salt marshes. Eels have been known to travel quite far to inland waters, some reaching the upper Mississippi river and the Great Lakes. Yellow eels, or immature adult eels, remain in this stage for five to twenty years. Eels are nocturnal predators, taking small fish, insects, worms, crayfish, and snails, and prefer to burrow in bottom sediment during the day. In winter, eels hibernate, burrowing into the bottom mud.
Females can reach two to three feet in length, and weigh three to four pounds.
Males tend to be smaller, around a foot and a half in length. Land-locked eels, however, can each five to six feet and weigh ten to fifteen pounds. The final phase of the eel's life is a series of dramatic transformations, and a long journey to the waters from where they were born. It's not known what triggers the change, there seems to be no correlation with age and sex. The change and migration usually occurs in the late summer and fall, as early as August in the north and as late as December in the south.