Can Fish See Fishing Line?

Introduction

When you try to catch fish, you use some kind of rig and line always. And you hope that the rigs are invisible for fish and your bait moves as naturally as possible.

Then it is a very important question to ask if the fish can see your rigs.

Expeiment

Kawamura (2011) is concluding that the fish may be able see the thin monofilament line clearly. 

He and his colleagues (Kawamura & Shimowada, 1993) had done the experiment to measure the fish’s ability to detect the contrast. And they had concluded that fish had much higher levels of contrast detection (55 times of humans).

This experiment uses the device like below, to train fish to react to certain shape with using the Pavlovian conditioning training. After fish are trained to recognize the shape, they change the contrast of the signal as independent variables.  

This picture shows the experiment device. The part showing numbers are emitting the stimulus with LED. The contrast of the signal was controlled by the brightness of the LED. 

The results of the experiment was telling us that fish had a higher ability to recognize the contrast, than normal humans. Compared to the result of the experiment done to the students, fish showed 55 times better ability to detect the contrast.

Conclusion

Fish have a much higher level of contrast detection ability. And it may be able to see the rigs and fishing lines in the water easily.

It seems reasonable to consider the fish see your thinnest line. What you can do then? ...

References

Kawamura (2011)、魚の行動習性を利用する　釣り入門、講談社ブルーバックス