When is Nylon-Mono Line Stressed Enough To Replace?

A couple of weeks ago as we discussed the frequent mislabeling of nylon-mono fishing line, one of our readers had an excellent question. If the line is stretched to its breaking point, nuclear_fisher wanted to know if the overall line was weakened by that stress and should he replace it?

As with so much of fishing, the answer is both "maybe" and "that depends...." Nylon mono is elastic to some degree. When stretched on a hookset or when fighting a fish, it elongates slightly and then returns to its original length when stress is removed. But when stretched close to the breaking point, that same mono will deform, becoming permanently elongated and less strong.

So the usual answer is yes. When you stretch your line in breaking off a snag, for example, you should probably replace it just to be on the safe side. (Note this also applies to nylon flyfishing leaders and tippets.)

But replacing line is a hassle, and maybe you don't really need to. This morning I took some 10-pound Ande mono, tied it to a snap with a Palomar knot, and then stressed about 30 feet of line until the knot broke. The stressed line and line fresh from the spool still tested about the same on my knot-testing machine. So I obviously hadn't applied enough stress to deform and weaken the line. No replacement needed.

What I suggest is this: If your line has been severely stressed, take about a 3-foot section between your two hands and pull. If the line still feels elastic, keep using it. If it seems like the line has lost its stretch, replace it. That's a simple and decidedly unscientific solution that will help most people.

On the other hand, if I were purposefully hunting record fish and wanted to take no chances, I'd re-spool. And you should always check for line nicks and abrasions, removing the affected line as appropriate. Then, too, re-tie your terminal knot--always--after landing a big fish.

Those who want to obsess about the finer points of nylon mono will find lots of information on Ultima's website, where this British linemaker does a great job of explaining the details. Otherwise, I'd say to hell with it and just go fishing.