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Alaska Science Camps, Fairs & Experiments

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Spearing Fish and
boatthe Refraction
of Light

 

For many centuries Native people of Alaska have lived from the abundant supplies of fish, those that remain locally and those that migrate.

There have been a variety of ways of catching fish:

  • Nets and dipnets
  • Fishtraps
  • Spearing
  • Hooks/lures

Day to day, a family's survival depended on the ability to catch fish.

In our area, we spear whitefish in the fall when ice is running in the river. We go out in boats at night. For lighting, we put a Coleman lamp in a five-gallon can that has been opened on one side. The five gallon can protects the eyes of the fisherman from the bright light, and reflects more light onto the river. From the front of the boat, we spear whitefish.

Spearing Fish and the Refraction of LightWhile the river is still running ice in the fall, we also chop a wide hole in the shore ice and spear whitefish through the hole.

Traditionally this was an important source of fish, as fish stored at this time of year can be frozen and kept all winter. Nowadays people can catch fish at any time and put them in the freezer. Spearing from a boat while ice is running isn't as important now, but it was and is an exciting adventure.

We also spear pike as they migrate between lakes in the spring. They are camouflaged quite well against the dark creek bottom, and are almost impossible to see as they swim in the creeks.

Spearing Fish and the Refraction of Light

To gain an advantage, we peel spruce poles, lash them together, and sink them with rocks. The poles are crosswise on the creek bottom. When the fish swim with or against the current, they show up clearly as they swim over the light colored poles. A white sheet or cloth held on the bottom by rocks serves the same purpose. However, if you spear too many holes in your mom's sheets, she will not be too happy. Wooden poles are better in that regard.

Years ago, before nylon nets were available, upriver people speared salmon from canoes. If king salmon are speared in the right place, just behind the brain, they quiver and die easily. If they are speared in the wrong place, the fisherman is in for a wild ride in his canoe!

ACCURACY IS IMPORTANT

The challenge 

It is exciting to spear fish, but our first efforts are usually frustrating. There is a science principle that must be understood before we can successfully spear fish. We see the fish, aim the spear well, and miss, again and again. Sometimes they are too fast for us, but other times, it seems that we are being tricked. The oldtimers understand the science principle quite well. That is why the older people can catch more fish than younger people even though the younger people are quicker and have better eyes.

Understanding Refraction

When light passes through air, it travels in a straight line. However, when light passes from the air to the water, or water to the air, it is bent, or refracted. When light passes through any two substances of different densities, the light changes speed and is bent.

We think we see exactly where the fish is. Actually, the fish is lower than we perceive. It appears closer to the surface than it actually is. If you put the tip of your spear in the water, it will seem bent.

The secret of spearing fish is to know how much below the image to aim the spear. The fish isn't where you think it is!

The greater the angle (from the vertical) the fish is viewed from, the more the light is bent. Spearing from directly above, the fish will appear to be in the same place, but will appear bigger and closer to the surface than it really is.

Spearing Fish and the Refraction of Light

Do you think eagles and other birds of prey that catch fish need to understand this science principle too? They must miss a few meals until they learn this science lesson.

Other applications

When sunlight passes through air, and then passes through a cloud or rain, we see a rainbow as the light is refracted and reflected within the raindrops.

White light is separated into the individual colors shown in the rainbow. (Look up Snell's Law for more information.)

Spearing Fish and the Refraction of Light 

Spearing Fish and the Refraction of LightWhen our eyes don't focus properly, we wear glasses that also refract the light, bending it in exactly the right way so we can see clearly.

Can you think of other applications of this science principle?

 

 

Experiment 

Make a long blunt spear. Hang a wooden fish (about 18") in the air and practice spearing it until you get Spearing Fish and the Refraction of Lightfairly accurate. Poke at the fish, do not throw the spear. If you hang it by two strings it won't spin as much.

Spearing Fish and the Refraction of LightWith that same spear, go to a clear creek, lake or river, and put the tip of the spear in the water. Does the part of the spear that is in the water seem to bend? Attach a target to a string (perhaps the same wooden fish). Attach the string to a weight and sink it so the target is 6" beneath the surface. Practice spearing the fish. How much below do you have to aim? Does this change with the depth of the target? Experiment at different angles, above the target and at a short or long distance. Imagine that if you miss, you will have to skip your next meal.

Try the same experiment with blunt spears of different weights and lengths. Which is best for you?

If it is winter, you can still do this experiment with a long washtub. Suspend one fish target over the tub, and sink one in the water. From different distances, test your skill, eye and estimation of refraction.

In the preceding experiments, what percentage of hits can you make for the fish out of the water? For the fish in the water? Which target is easier to hit?

If you are practicing on a creek, river, or lake, do this experiment on a sunny day, and on a cloudy day. Try it with the sun at your back or in your face. Do it at dusk after the sun has gone down, but before dark. Try the same experiment with different kinds of light at night (flashlight, strong flashlight, Coleman lantern, torch.) What differences do you notice? What conclusions can you draw from this? What are the best conditions to spear fish? What are the worst conditions? Do Polaroid sunglasses help?

Ask the oldtimers in your village what kinds of fish they used to spear. What time of year did this occur?

What were the best conditions for this activity (night, day, calm weather, etc.?) What were the best locations? Ask them how they stored those fish. Is this activity still possible today? If possible, try it. What kinds of spear heads were used in the recent past? Were they store-bought or homemade? If they used homemade spear heads, make one according to their directions. What kinds of spear heads were used long ago?

Ask the oldtimers in your village where the fish are going and where they are coming from when they were being hunted. Why are they traveling in the river or creek? What is the advantage of spearing over hooking?

Find what the Alaska Department of Fish & Game know about the fish in your area. Compare their knowledge with that of the local Elders.

Finding and Developing a Science Fair Project

Examples of "Observe and Think" Projects

200+ Ideas for Science Fairs!

Traditional Lighting

Firestarting

Traditional Firemaking

Sharpening

Fishing with Lures

Rabbit Snares

Spearing Fish and the Refraction of Light

Chill of the Campfire

Solution vs Suspension

Seals & Beaver, Floating & Sinking

Steaming

Selecting a Birch Tree

Spruce & Other Roots

Spruce Gum

Spear Throwing

Berry Pickers

Drum Frames

Conclusion

 
Book Cover

© 2004 Alaska Native Knowledge Network. All rights reserved.

A partner with the Alaska Rural Systemic Initiative

This material is based upon work supported by the National Science Foundation under Grant No. 0086194. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Contents

Camps as an Environment for Science & Culture

Culturally Relevant Science Fairs

Experiments

 

 
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Last modified April 12, 2011