The Savage V-24 in 30-30/12ga is my favorite survival gun.  It also was my first gun back when I was a teen.  Just one problem with it, it's awful heavy.  I am afraid that the tendancy would be to leave it leaning against a tree, or on the bank while you fish.  
Is it enough gun?  Well that depends, if you can wait till the target is real close.  YES!  The 12ga that is.  The 30-30 is a little light for most things here.