Fishy Business

By David Price

The first day of the fishing season…

David is science made simple's expert angler! CC-BY science made simple

David is science made simple‘s expert angler! CC-BY science made simple

You get up bright and early and head to the river equipped with all the best baits, lures and tackle anticipating all the fish you are going to catch. But by the end of the day you still have not caught a single fish! All of that initial excitement is replaced with disappointment and you go home empty handed!

Maybe the fish simply were not biting that day? But why? What could we know about fish senses that could help improve out chances of catching them next time?

CC-BY-André Karwath

CC-BY-André Karwath

The eyes have it!

Fill a tall jug with water and dunk about half the length of a pencil into it. Now carefully look at the pencil. You should notice that it appears to be bent! This is a phenomenon called refraction and is caused by water bending light so it appears at a different angle.

This gives fish a very odd (to us) view of the world above the water surface.  They see the world beyond the water through a cone of light reaching from their eyes to the surface at an angle of 48 degrees.  So everything they see above the water is only seen through a circular window of light.

Fish have a narrow window where they can see, so stay low when you fish to avoid scaring them! CC-BY science made simple

Fish have a narrow window where they can see, so stay low when you fish to avoid scaring them! CC-BY science made simple

 

If any wild fish sees us it’s going to swim away and hide fast! On the whole fish do not want to be caught, and they see us as a threat.  Next time you are on the riverbank try to keep as low as possible. This will help to keep yourself out of the fishes cone of vision, making it much more likely that the fish will take your bait :)

But even if we keep low and below the skyline sometimes those clever fish will still know we are there.

Fear the growing of the shadow!

CC-BY-Purityofspirit

CC-BY-Purityofspirit

Standing, looking across the river with the sun on your back might feel very nice, but what can very easily happen is that you cast a shadow onto the water. Shadows are the patch of ground that the sun’s light cant directly get to because something (in this case, you) is in the way.

Any experienced angler will tell you that your shadow can be a mighty scarer of fish! This problem can even challenge those who choose to fish at night! On a clear night the reflected light from a full moon can cast a really strong, fish-scaring shadow onto the water.

Keep your shadow off the water by:

  • Keeping as low as you can again can really help by making your shadow as short as possible.
  • If you can fish both sides of your river or lake, you should be able to arrange your fishing time so that the sun is always casting your shadow away from the water, by always facing the sun as you fish.
  • Fish on a cloudy day.

Bad Vibrations (don’t throw stones!)

Pollock have a really obvious lateral line. CC-BY-Tino Strauss

Pollock have a really obvious lateral line. CC-BY-Tino Strauss

On several occasions I have caught completely blind fish.  Fish must use some sense, other than sight, to help them to find out what is going on around them?

Next time you catch a fish and hold it in your hands (remember: wet your hands first and do not to keep it out of the water too long!), have a look on the side of the fish and you should see a faint line running down its body from head to tail.  This is called the lateral line, it’s made of a series of cells connected to microscopic hairs that are very very sensitive to vibration.

The lateral line can pick up vibrations from:

  • Its dinner, like a worm struggling in the water
  • The presence of a bigger fish that might eat it!
  • The maggots on your hook
  • The sound of you stamping up and down on the river bank!

Through its lateral line a fish can sense the world around it.  Vibrations travel around 4 times further in water than in air.  So if you want to catch lots of fish, don’t stamp around on the riverbank and scare them all away. Remember to walk quietly and don’t throw stones!

For successful fishing, just remember:

1. Keep yourself below the skyline (no see)

2. Keep your shadow off the water (no see)

3. Walk quietly (no feel)

By understanding some fishy science you will catch more fish! Happy angling and remember the first rule of fishing: Don’t Throw Stones!

 


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Posted in Biology, Exploring Science, Physics