Wild salmon finds home - an activity
We have called this activity the smell game. It's about how wild salmon find their way back to the river they grew up in after a journey of several thousand kilometers in the ocean.
Competency objectives, grade 7, Science
- ask questions and make hypotheses about scientific phenomena, identify variables and collect data to find answers.
- explain how organisms can be divided into main groups and give examples of the characteristics of different organisms.
Do you think this "river" smells like what it says on my note?
Wild salmon almost always find their way home
After a nutritional migration of several thousand kilometers in the sea, wild salmon return home to spawn. They almost always find their way back to the river they grew up in.
The wild salmon even finds its way to the spot in the river where it was an egg. How on earth does it do that?
Built-in compass
Wild salmon have magnetic iron in their heads and lateral line organs. This helps the salmon to register the Earth's magnetic field, just like a compass does. This helps them find their way to the coast.
Good nose
When it reaches the coast, another sense takes over: the sense of smell. The salmon follow the smell of their river the last part of the way home.
This group has reached the coast and caught the scent of their river. Now they're almost home. Photo: Audun Richardsen
This is the smell game
The teacher lays out three ropes on the ground. The ropes should represent three different rivers. At the end of each rope, the teacher places cups that are covered as in the picture above. The contents of the three cups have different smells. The teacher gives you a note telling you which smell to find. If your note says raspberry, you are a raspberry salmon and must smell your way to the raspberry river.
Before you start, you need to know the following:
Salmon can't talk, so in this game no one has to use words. It's more fun if no one knows what's on your note.
When the starting gun goes off, there's no need to rush. It's early summer and there's still a long way to go before you need to find your spawning ground.
Follow the ropes and smell all the cups.
Stand in the "river" you think has the smell on your tag.
Remember, you are all winners! Only 5% of smolts that migrate to the sea actually return to the river!
Choosing the wrong river is not wrong
Occasionally, salmon swim up a different river than the one they grew up in. As long as there are few salmon, this can actually make the salmon in the river a little stronger.
For the teacher
This activity is perfect after reviewing the salmon's life cycle and working with the senses.
Practical preparation: Get out 3 paper cups, 3 rubber bands, 3 cloths (disposable kitchen cloths work well) and 3 ropes. If you choose to print out the attached file of notes, you will need some raspberry jam, some mackerel in tomato and some banana.
The game is played as described, and can be summarized as follows:
- Did all the salmon find the right river? Detect the smells and find out if any have wandered off course. Wrongly migrated salmon haven't done anything wrong. They can stay where they are.
- How many salmon were in each river?
- Which river has the most female salmon?
- Which river will have the most young salmon next year? The point here is that it is not necessarily the river with the most salmon that will have the most young salmon, but the river with the most female salmon.
- A river with only female salmon is obviously in a bad position. If this happens, you can ask if something is missing from one of the rivers.
The female salmon produces the eggs (1450 eggs per kilo body weight) and is therefore most valuable to the river. A male salmon can fertilize the eggs of several female salmon. In many salmon rivers, there are rules that require female salmon to be released at the end of the season.
Student booklet
The Nasjonalt villakssenter works for a stronger wild salmon and wants to promote the stream as an educational resource. Bring experiences from the classroom and put them in context with experiences outside. Many schools in Norway have a local stream. Even in our largest cities, there are streams you can visit. Contact us if you would like help, tips and professional development.
The student booklet Who lives in your river? can help with both preparation and follow-up work.