Monofilament Fishing Line

Line links the angler and the fish that they are aiming to catch, and it is therefore worthwhile spending time thinking about the type, strength and quality of line that will be used. The most popular line in the UK is monofilament (often referred to as simply ‘mono’). This is a line made out of a single fibre of plastic by heating and mixing the polymers and forcing them through tiny holes to produce line of the required diameter and strength. Monofilament is fairly cheap and an effective fishing line, accounting for its popularity throughout the UK, and indeed the world, although braided fishing line has become increasingly popular in recent years. Before monofilament existed anglers had to use line made out of a range of different materials, all of which were vastly inferior and much harder to use than monofilament (see below).

Line for Reels

Fishing Line Strength, Diameter and Strength

The strength of monofilament refers to the maximum weight that this line will hold, but every time a knot is tied in monofilament the overall strength of the line is reduced. For this reason, rigs that use fewer knots (for example by using trapped swivels rather than dropper knots) will be stronger than rigs featuring a high number of knots. Most anglers find that using a main line of 15lb breaking strain (with a shockleader) is sufficient when fishing over clean ground, but anglers fishing rocky or snaggy marks may use a main line which is up to 35lbs breaking strain. Monofilament line is not very abrasion resistant and will easily become damaged if it is allowed to scrape over rocks or railings, especially if it is under tension when it does so.

The stronger line is the higher its diameter will be. Monofilament of around 15lb is usually 0.35mm in diameter, with stronger 30lb monofilament being around 0.50mm in diameter. This may not sound like too much difference but stepping up the thickness of line has a big impact on both casting distances and how much line can fit onto a reel. Monofilament is also stretchy, which is both a strength and disadvantage – the stretchiness allows mono to have some forgiveness in casts and means that there is a buffer between the angler and the fish when striking or playing a fish, but it also means reduced bite detection and contact with the fish. Stretch free braided line has been available to UK anglers for some time now, but this type of line brings its own advantages and problems.

Fishing Line Manufacturers and Quality

Unbranded Line
Avoid cheap unbranded line as there is no guarantee of quality.

When it comes to monofilament line there are plenty of well-known manufacturers (such as Impact, Maxima, Tronix and Daiwa as well as many others) which make high-quality line for a reasonable price, so it makes little sense to buy line from an unknown or unbranded make. Others manufacturers such as the American company Sunset make specialist snood line, such as their Amnesia brand. Extra-heavy monofilament with a breaking strain of 100lbs or more and wire line is also available for hooklengths for powerful species with sharp teeth which may be capable of biting through weaker monofilament lines.

Using Monofilament Line

When choosing a line for fishing from the shore with a standard beachcaster rated to cast 4 – 8oz there are two ways of setting up a reel with line: a light main line can be used with a shockleader or a stronger main line all of the way through with no shockleader.

Light main line and shockleader: The first way is to use a light mainline of 12 – 18lb monofilament, this line is strong enough to successful reel in a fish, but light and thin enough (usually around 0.35mm in diameter) to allow anglers to cast to their maximum distances. However, because this line is so thin and weak the force of a cast will easily snap the line meaning a shockleader needs to be used. This is a length of heavy mono, typically 50lb or more in breaking strain, which is attached to the end of the main line to absorb the force and power of a cast. A shockleader needs to be long enough so that when the weight is in place ready to cast there is around 6 – 8 turns of shockleader around the spool. Shockleader is attached to the mainline using a special adaptation of the uni knot, and tapered shockleaders are available which produce a much slimmer knot.

Impact Monofilament
Impact Monofilament 14lb breaking strain is a good choice for main lines when used with a shockleader.

The 12 – 18lb mainline and 60lb shockleader is the typical setup for shore fishing on clean ground. Working out the strength a shockleader should be is easy as it follows a simple formula of 10lb of breaking strain for every ounce of casting weight (see panel above). Both multiplier and fixed spool reels work well with weaker mainline and a shockleader. WSB Impact Monofilament is available in 12lb or 14lb breaking strains making it ideal for use in this type of set up. It can be purchased from Sea Angling Shop in clear colour by clicking here and in hi-visibility yellow by clicking here.

WSB Tapered Leaders which are available in clear or high-vis yellow colours. These leaders are 60lb breaking strain but then taper down to 15lb breaking strain, meaning that the shockleader knot is smaller and more streamlined and compact, meaning it is less likely to collect weed or catch on rod rings during a cast.

Red Ice
Many brands of line in 30lb breaking strain can be used without shockleaders, as long as simple casting is used.

Straight through line: When fishing rough ground and marks with constant snags many anglers use an alternative setup. This does away with light line and a shockleader and instead has the same strength line all of the way through from the reel to the rig. This line is always stronger and thicker, typically 30 – 35lb breaking strain. The reason for this is that when getting snagged with a light line and shockleader the line will always snap at the join between shockleader and main line as this is the weakest point. In a fishing session where getting snagged is a regular occurrence this will mean constantly going through the fiddly (and costly) job of tying on new shockleaders. For this reason anglers fishing snaggy marks use a straight through line as this will always snap at the rig, meaning the line can be reeled in and a new rig attached with minimum fuss. However, casting distances will be reduced as much thicker line is being used and it is very important that only overhead casts should be performed. It is not safe to perform power or pendulum casts with no shockleader. Anglers should avoid using line that is too strong to cast with – any stronger than 35lb and line will be so thick it will cut down casting distances considerably, and can also prove very difficult to snap when caught in a snag. Again Impact Monofilament in its 33lb strength is a good choice for anglers looking to use a straight through set up – it is available in hi-vis yellow colour by clicking here or clear colour by setting here.

Multiplier reels definitely work better than fixed spool reels when fitted with 30lb line straight through, as the bulkiness of the line makes the line level plummet on a fixed spool reel which increases friction and seriously reduces casting distances. Fixed spool reels can still be used with 30lb line as long as anglers are aware that casting distances will be reduced considerably (this may not matter on deep-water rock and pier marks where casting distance is less important).

Line for Bass, Flattie and Spinning Rods

Spinning Reels
Light spinning reels can be used with relatively weak line straight through.

When using lighter rods and monofilament most anglers use straight through line and do not bother with shock leaders. This is because these rods are used to cast relatively light lures and weights and are only used to perform basic overhead casts (not power or pendulum casts). With bass or flattie rods which generally cast lures or weights of 2 – 4oz anglers usually use line of around 15 – 18lb breaking strain. With smaller, lighter spinning rods, which may cast lures of only an ounce or so, anglers can step down to a main line of around 10lbs with no need for a shockleader, as long as only simple overhead casting styles are used. With the rising popularity of LRF (Light Rock Fishing) anglers can cast lures weighing just a few grams on monofilament lines of 2 – 5lb breaking strain.

Line for Making Rig Bodies

A number of different types of line are used for making rigs, ranging from near-invisible flurocarbon lines for rigs to catch stealthy and shy-biting fish to heavy wire which are used to prevent powerful species with sharp teeth from biting through the line. Read on to find out more about the different types of line used in the construction of sea fishing rigs.


Rig Body

Trace Builder Rig Body Line
Trace Builder Rig Body Line is ideal for making rigs.

Rig body line is simply the line which makes up the main ‘body’ part of a rig. Due to the fact that rigs will be dragged over the seabed as they are reeled in, and will often have crimps pressed onto them and knots tied into them, anglers usually use line which is at least 60lb breaking strain. Trace Builder Clear Rig Body Line (pictured right) is a good value choice for rig body line. Often anglers buy two spools from the tackle shop and using one for leaders and keeping one to use for making rigs. Obviously, line used for rig bodies needs to be at least as strong as the line being used for the shockleader. There would be safety implications if an angler cast 8oz weights with an 80lb shockleader but used rig body of 40lb line. Anglers should be aware that it may be difficult to fit crimps and tie knots in very thick line which is over 80lb in breaking strain.

Hooklength and Snood Line

Amnesia is a memory free line which is popular for hooklengths.

A hooklength (also known as a snood) is the length of line which terminates in the hook. Anglers typically use a monofilament line which is memory free for snoods and hooklengths. Memory free line does not retain the curvature of the spool it was wrapped around, making it much less prone to tangling and therefore ideal for hooklengths. Sunset’s Amnesia line is probably the most well known and popular memory free line used by UK anglers, but others such as WSB Specimen Mono is also a good, and cheaper, line for this purpose. Genrally 15lb to 30lb breaking strains are the most commonly used for hooklengths. Anglers targeting large species with sharp teeth such as conger eels and sharks may use wire line for their hooklengths as these species may be able to bite through monofilament line – read our full article on wire line by clicking here. Fluorocarbon is a modern type of monofilament line which is strong and abrasion resistant, as well as being practically invisible underwater. For these reasons it is becoming increasingly popular for hooklengths in sea fishing, although it is expensive compared to standard monofilament. Read the full article on snood and hooklength line by clicking here.

Weak Link Line

Weak Link Diagram
Weak clip with mono.

When fishing rough ground anglers often use a rig which has a weak link release (also known as a rotten bottom) built into it. This is an item of terminal tackle which connects a weigh to the rig via a short section of weak monofilament line. If the weight becomes snagged while reeling in the weak link will easily snap, but if no snags are encountered then the weak link will allow the rig and weight to be retrieved. The diagram to the right shows a Cronus Weak Link Clip being used with a short length of weak monofilament. Most anglers have a spool of weak monofilament line of around 10lbs breaking strain which is kept in the tackle box and used to make any weak link releases which are needed during the fishing session.

Power Gum

Power Gum
Power gum is the best choice to make stop knots with.

Power gum is a specialist type of line that is used in freshwater fishing as a way of making shock absorbing sections of line, but is only used in sea fishing as a way of making stop knots. Stop knots made with power gum are effective as they stay in place well, but can still be moved under a little pressure. Power gum stop knots are based on the uni knot and can be used for making bait stops, trapping swivels or securing an impact shield in place. Just like line power gum comes in breaking strains with 10 – 15lb power gum being the best for stop knots. In recent years the use of power gum has declined in popularity in sea fishing, as anglers switch to making stop knots with other materials such as Gemini’s Neoprene Rig Tubing.

Line Colour

A quick look around any tackle shop or online tackle dealers will reveal that monofilament line is available in a wide range of colours, ranging from clear to super high-visibility fluorescent yellows and reds. While these high visibility lines make it easier to see where line is (a big advantage on a crowded fishing venue such as a pier), clear lines allow the reassurance that fish are not spooked or put off by a brightly coloured line. In reality the majority of sea fish are fairly unfussy feeders which are highly unlikely to be put off by line colour, even when fishing in bright daylight. However, anglers targeting shy-biting fish such as mullet (and to a lesser extent bass) generally use clear monofilament, or possibly flourocarbon, to eliminate the risk of frightening off any fish. We have a guest post written by top US competition angler Tyler Brinks discussing whether or not fish can see line which can be viewed by clicking here.

Before Monofilament Fishing Line

The ubiquitous nature of monofilament means that many anglers do not realise the range of different types of line which anglers used in previous generations – and how difficult these lines were to use compared to monofilament. The book The Technique of Sea Fishing and Tackle Tinkering by W. E. Davies which was originally published in 1952 and revised in 1962 and lists cuttyhunk (flax), cotton, silk, plaited nylon and nylon monofilm (sic) as all being lines which were commonly used by anglers at the time, although the book warns that nylon monofilm in breaking strains of over 8lb can be “too springy and difficult to handle” (p 22). Many of these non-nylon fishing lines would have to be removed from the and hung outdoors to dry after every fishing session, otherwise they would rot. Indeed, the book provides a method of dressing line to make it last longer and become less water absorbent. Anglers have to mix Stockholm tar, turpentine and methylated spirits in a jar and then coil the fishing line and place it in the solution and leave it there for two days, before removing the line and letting it dry (which took two weeks) and then re-winding it back onto their reel through a cloth. It is easy to forget how much easier modern monofilament fishing lines are to use and maintain compared to the lines which were used before monofilament was available.

Sea Fishing Line and the Environment

Bird with Fishing Line
Marine birds tangled up in fishing line create a terrible image of anglers.

Related article: Responsible Sea Fishing

Anglers should always take great care to dispose of any type of fishing line safely. Line which has been carelessly (or, even worse, deliberately) left around a fishing area is a real threat to the marine environment and will remain so for decades as monofilament will take many years to biodegrade. Images of sea birds tangled up in fishing line puts anglers in a very bad light and can be used by local councils and wildlife pressure groups to get the public onside in campaigns to ban angling. The way of dealing with this situation is simple: anglers must take excess line home with them and dispose of it responsibly. There is currently a national scheme in place to allow anglers to recycle fishing line – visit their website by following this link.