I have been told that tuna fish balls are a great bait to fish for Salmon. How do you "tie up" the tuna fish balls and what is the best way to attach them to your line (just above the hook, I think)?
The best thing to use is moline. It's a tough mesh material that holds the tuna (and other secret ingredients). Cut the moline into 3" by 3" squares, lay-in your bait, and gather the four corners. Tie the top of the ball off with thread or a fine string using a couple of half-knots to secure the thread end. Then, run your hook through the ball of material. This same material also works well for holding clumps of salmon eggs, as well.
Moline can be found at most sporting goods stores that sell salmon and steelhead fishing equipment.