Check the side of the spool for line diameter info and let that be your guide for your shore angling application.

Thick & thin of line

Australian shore anglers don’t seem to pay much attention to the diameter of their main line, at least compared to shore anglers from other countries. For as long as I can remember we seem to be more obsessed with breaking strain than line thickness. Although the two measurements are to some extent related, there is plenty of variation of line diameter for a given breaking strain. Let’s take a closer look at how shore anglers can use line diameter to their advantage.

Casting distance is often an important consideration for the shore angler. This is especially the case on open surf beaches where desirable gutters can sometimes be over 50 metres away. Thin diameter lines can obviously be cast a lot further than thicker lines. The reason is twofold. The thinner the line, the less friction created where it contacts the guides as it flows off the reel hence the casting effort has less friction losses, imparting more energy into the rig itself. Secondly and more significantly thinner lines experience less drag from the air itself. This is especially apparent when casting into a headwind. In an ideal world we would all fish with the thinnest line possible to make the casting process as efficient as possible.

Another consideration is line visibility. Thinner lines are less visible in the water. Of course your leader visibility will be of higher importance than your main line visibility as it is closer to the bait or lure, but nevertheless thinner lines will be more likely to go unnoticed in the water.

Are there any disadvantages to using very thin lines providing the breaking strain is adequate for the application? Most definitely!

The first major disadvantage is the general lack of robustness in thinner lines. This can be an obstacle to landing tough fish for a variety of reasons. Any line contact with a foreign object will damage all lines to some extent. The thinner lines are especially vulnerable in this regard. You might be surprised how easily your main line can get damaged and fail. Apart from the obvious potential for sharp objects like rocks to damage line, even hard-edged sand banks can rub and fray. Seaweed can also do terrible damage to your main line especially after winding in repeated clumps of it on those bad days. What about the fish themselves? Sharks in particular have very abrasive skin that makes short work of thin line. Many times I’ve lost my rig and a long leader when a shark has powered off into the night. I suspect they spin their bodies and wrap the stronger leader around themselves until the main line makes contact and fails.

That same lack of visibility that makes thin lines an advantage when outfoxing fish can make life hard for the angler when we need to see where our line is going. Invisible line makes it harder to steer around reef ledges, weed clumps and other obstacles we might want to avoid.

Thirdly, thin lines can be tough on your casting finger assuming your leader isn’t long enough to be on the reel when casting.

Something you might not have given any consideration to is the effect line thickness has on lure action. In particular diving lures and their ability to get down in the water column. Generally speaking thinner lines allow diving lures to dive deeper while thicker lines restrict lure depth. You can use this to your advantage to manipulate how deep your lures run.


Everything I’ve mentioned so far is applicable to both nylon and braided fishing lines. Given braided lines are generally a lot thinner than nylon lines of the same breaking strain anglers haven’t needed to think so much about line diameter since braid has become so popular. However nylon line is still the line of choice for many beach anglers. My beach casting overhead reels are normally spooled with 15kg breaking strain nylon main line, so I thought I would look at some of the popular lines on the market and get a feel for how the diameter varies amongst them in the 15kg class.

Two nylon lines I have used extensively in 15kg are Rovex HT Monocast and Platypus Lo-Stretch. Both of these have a diameter of 0.45mm. This measurement would be considered on the thin side of average for 15kg breaking strain mono line. At 0.45mm, they offer reasonably long casts without compromising toughness too much. This also helps increase spool capacity which is handy with long-running fish.

The thickest diameter commonly available for 15kg would be around 0.5mm whilst the thinnest would fall somewhere around 0.42mm. Now 0.08mm of variation doesn’t sound like much does it? In reality there is a massive difference between 0.42 and 0.5. I would estimate on a typical long cast off a surf beach you might expect 10-20 metres of distance variation between the two diameter extremes depending on the wind.

The effect on line capacity is even more dramatic. Just take a look at the writing on the spools of any typical thread line reel. My big Fin-Nor Offshore 7500 tells the story only too clearly. It will swallow 439 metres of 0.40mm line but only 274m of 0.50mm line. A difference of 165 metres. A 37 per cent difference. On my Penn Torque 100 surf casting overhead a 0.05mm diameter difference can add or subtract the best part of 100 metres to the line capacity. That’s enough to win or lose the battle with that big bronzie you’ve hooked.

At the end of the day only you can decide which line diameter is right for your fishing. I’d suggest for shore angling in general line diameter is far more important than straight breaking strain. In fact I only really look at breaking strain as a guide to finding the diameter that will suit the application. After all when was the last time you snapped a line in a straight tug of war with a fish because the line was too weak? In reality it rarely happens and line failure normally results from damage to the line itself.

Caption Check the side of the spool for line diameter info and let that be your guide for your shore angling application.