Can Fish See Your Fluorocarbon Line?

Fishing lines have been around a long time and fluorocarbon lines are the newish kid on the block. Fluorocarbon line manufacturers make many promises about this fishing line’s advantages. One of the main selling points is that the line is almost invisible in the water.

Is this really possible? Can fluorocarbon lines be that difficult for the fish to see?

Fluorocarbon is essentially invisible underwater and is least visible than any other fishing type of fishing line. This is due to fluorocarbon having a refraction index similar to that of water.

Fishing is an activity that is associated with exaggerated claims. Newer gear with seemingly outlandish claims will be viewed with some skepticism.

How low is the low-visibility of fluorocarbon line, and does it really make a difference to your fishing?

Fluorocarbon Line Hard To See

What Affects Fluorocarbon Line Visibility In The Water?

Fluorocarbon fishing lines were originally developed in Japan, where avid bass anglers were looking for a way to get shy fish to bite. The line was manufactured with certain qualities, giving anglers an advantage.

Heavily fished waters can cause fish to become line-shy. This means fish have learned to associate visible lines with artificial lures. If a fish sees the line with a lure, it will be more reluctant to bite.

The low visibility of fluorocarbon line in the water was only one of the features of this new product that gave anglers the edge they were looking for.

Features Of Fluorocarbon Line

Fluorocarbon is made from a particular type of plastic called polyvinylidene fluoride (PVFD). Fluorocarbon’s manufacturing processes can be adjusted to change the characteristics for different angling applications.

The main benefits of fluorocarbon lines are:

  • Line strength. Fluorocarbon is stronger than monofilament.
  • Line sensitivity. Fluorocarbon offers more sensitivity on the line, giving the angler a better feel for what is happening at the end of the line.
  • Abrasion resistance. Fluorocarbon is resistant to wear from abrasion.
  • Fast sinking line. Fluorocarbon sinks faster than other lines due to its higher material density.
  • Low water absorbency. Fluorocarbon doesn’t absorb water and becomes waterlogged, unlike monofilament.
  • Chemical and UV resistance. Fluorocarbon is resistant to damage from chemicals such as fuels and oils. It doesn’t degrade when exposed to UV radiation or sunlight.
  • Low refractive index. The line reacts differently to light than other line types, reducing its visibility in the water. 

Refractive Properties Of Fluorocarbon Line

The reason why fluorocarbon lines are practically invisible underwater is due to their refractive properties. Refraction describes how fluorocarbon bends light, and this is where its advantage in the water comes to bear.

The refractive index of fluorocarbon line is very close to that of water. The refractive index of water is 1.33, and fluorocarbon line is close to it with an index of 1.42.

This means that the line bends the light passing through it, similar to how water bends light. This effectively makes the line react to light similarly to water, making the line less visible in the water.

When light hits an object, specific light wavelengths are absorbed, and some are reflected. The colour we perceive on things is a consequence of the light wavelengths reflected rather than the ones that have been absorbed.

Why Is Fluorocarbon Line Not Completely Invisible Underwater?

Many other factors influence the visibility of any fishing line in the water, including the following.

  • Fishing depth. The deeper in the water your line sinks, the less the light penetrates from the surface.
  • Colour fade. With depth in the water, specific colours fade out and are no longer visible and appear grey or black. This can increase the contrast visibility of lines at particular depths in the water.
  • Clarity of the water. This will affect the depth to which surface light will penetrate the water.
  • Particles in the water. Particles suspended in the water will scatter the water’s light and affect how colours are perceived below the water.
  • The angle of the sun. The angle at which the sunlight penetrates the water can affect the line’s visibility since the surface layer of the line may reflect light from certain angles.
  • Level of light. Overcast days or clear sky days will affect the amount of light entering the water and, thus, the line’s visibility. 

Fluorocarbon lines will retain a certain level of visibility in the water but will be less visible than other types of lines.

Why Does Fluorocarbon Come In Different Colors?

If fluorocarbon lines are practically invisible in the water, why does fluoro come in different colours?

The reason fluorocarbon line manufacturers produce lines of different colours is to compensate for the clarity levels in different waters and the colour fade in the spectrum at certain depths in the water.

The spectrum of colours we see, namely red, green, blue, black, and clear, is a combination of absorption and reflection of different light wavelengths. For example, if an object appears to be red to us, it has absorbed all the other light wavelengths but reflects the red light wavelength.

Consequently, we need a full spectrum of light to see colour to perceive the colours as they really are. In the absence of a full-spectrum light source, the colours fade out or darken, and we cannot see the actual colour, but instead, they become a contrast to the surrounding environment. This sometimes causes certain colours to stand out more in contrast when the colour has faded than other colours.

Light Penetration In Water Affects Fluorocarbon Line Visibility

Different colours have different waveforms in the light spectrum, with some being longer than others and some being shorter. This affects the penetrating power of the different light wavelengths. For this reason, colours wash out with increasing depth in the water.

Fluorocarbon line manufacturers make lines in different colours to cater to different water visibility conditions and variations in depth. This gives anglers a choice for which line colour will best suit their fishing conditions.

The major light colours disappear at the following depths.

  • Red. This colour disappears first at a depth of about 10 feet.
  • Orange. Orange fades out at a depth of 15 to 18 feet.
  • Yellow. The colour yellow fades at a depth of about 35 feet.
  • Green. Green holds its colour underwater to a depth of 45 feet.
  • Blue. Blue is the colour that lasts the deepest in water, down to 100 feet.

Research has shown that the most suitable and effective fluorocarbon line colour is pink. This colour blends the best into the background underwater. It is not a solid colour, but it still allows light to pass through the line.

While some macho anglers may not want to use pink fluorocarbon lines in any shape or form. Other more open-minded anglers have had great success with this line at various depths and water clarity conditions!

How Do Fish See Perceive Fluorocarbon Line Underwater?

Our discussions thus far have been how humans perceive light and colour at depth in the water, but what is fish vision like, and do these factors affect what they see in our fishing lines?

It is tough to establish what the vision of other animals is like, including fish. Studies have shown that fish perceive some colours better than others, while contrast plays a more important role in their vision than colour for other fish.

Bass is a popular sport fish, and much of the studies regarding fish vision have been conducted on these fish. Research has shown that bass sees colour, but warm colours such as red, orange, yellow, and green are seen as bright colours.

The darker spectrum colours such as blue to purple and black are less important to bass, and thus their perception of these colours is weaker.

To see how this may have a bearing on your fishing line colour choice, let’s use red fishing lines as an example for bass fishing.

  • Shallow water fishing. In shallow water of around 5 feet, the red colour will be clearly visible to the bass, and the fish may shy away from the line at this depth.
  • Medium depth fishing. The red colour would have disappeared at a water depth of 10 to 15 feet, and the line will appear grey, which may blend into the background more and encourage bass to bite at this depth.
  • Deep fishing. At a depth beyond 15 feet, the red line appears black, which may contrast with a light background, making it more visible to the bass at this depth.

What Color Fluorocarbon Line Should You Use?

Suppose you’re interested in trying out fluorocarbon fishing line for yourself to gauge its performance in your fishing grounds. What colour line should you opt for?

As suggested, pink fluorocarbon lines have shown the best results in the widest range of conditions.

If you simply cannot see yourself climbing onto your fishing boat with pink line on your reel, then a clear fluorocarbon line is the next best choice

Fluorocarbon line also comes in a green tinge colour and can be used when fishing in waters with a similar green tinge. This will result in the line more closely mimicking the water colour while retaining low visibility!

I would recommend starting out with a clear fluorocarbon line as a general-purpose line suitable for most water conditions.

Other Ways Fish Detect Prey In The Water

Colour isn’t the only tactic predatory fish use to hunt their prey. Fish have many hunting techniques in their bag of tricks to find food, which anglers try to exploit to try and get the fish to take their bait.

Eyesight is one method that fish use to find their food, but other aspects can include the following.

  • Vibrations. Many fish species use vibrations in the water to detect floundering prey or prey movement. This is often achieved by special cells in the fish’s lateral line that are sensitive to water pressure variations created by vibrations in the water.
  • Flash. The flash of reflective colours such as silver and the flash of movement attract predatory fish to prey.
  • Scent. Scent plays an important role in fish looking for prey, especially in murky water where the fish’s eyesight is of no advantage except when very close to the prey.

Fluorocarbon line offers benefits in the vibration department of the lure. The line sinks faster than other lines, allowing lures to assume a more natural posture, mimicking the fish’s natural prey more closely.

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