The Kennebec is a long river; depending on where you fish it there are different fish to catch.
Up by Moosehead it's Landlocked Salmon and sometimes brook trout (the ponds up that way have lotsa small brookies and around the 4th of July there are enormous HEX hatches requiring size 8 & 10 drys!)); if you move down river near Bingham it's rainbows and then there's the Solon and Madison tailwaters with browns and then further down in Fairfield below Shawmut dam (once awesome but not as good anymore) it's rainbows and browns, below Waterville it's browns, smallies and stripers.
The lower Kennebc has had several poor years on stripers but was awesome 10 years ago; they don't seem to come up the coast like the did and nobody knows why for certain.
If you plan to go there contact me and I'll get you hooked up with the right places,flies and people so you'll have a great time.... Up there I'm sorta famous when it comes to flyfishing and rivers.... down here I fish in obscurity! LOL