On Sun, 22 Jun 2008 08:06:27 -0700 (PDT), "
wrote:

On Jun 22, 7:23?am, Paul Cassel
wrote:
Guys with a lot of experience claim when that sort of line break occurs,
it's almost always a shark responsible.

Could be but 20 pound test is very light tackle. With line that light
you'll need to stop the boat or even back it down and take it really
easy for any decent sized ocean fish. I hand line and use 200 pound
test and I've had that broken twice. With a reel you can set the drag
light enough to use small line but you'll need to play them all day.
If you want to catch fish (rather than records) I think 60-80lb plus
10+ feet of 200-300lb leader is about right... With reasonably heavy
tackle you can pull them right in and kill them fast. For fish less
than about 30lbs you can just grab the leader and lift the fish
aboard, throw a towel over it and brain it.

A few things that may or may not be relevant, because they're
elementary fishing advice.
Knots - are you using the "improved clinch knot" to tie off line to
leader/lure? Any curl at the break point indicates the line broke at
the knot. As I recall testing showed the improved clinch was good for
95% of line test strength. Other knots were in the 80% or less range.
Line degradation - Sun and fraying/nicking greatly reduces line
strength.
Drag - a smooth consistent drag is essential. Depending on how much
attention you're paying to the rod, having it initially set as light
as possible is best.
This allows you to gradually tighten it as needed to tire the fish
before it can break the line or run it all out, instead of giving it
the opportunity to apply all its strength to the line when its
strength is at its greatest.
But if you're not paying attention chances are higher a big one runs
the line off the spool and takes it all.

--Vic