Kokanee Salmon - STEM Challenge
Natural Selection Kokanee Salmon
A Quick Background
About 15,000 years ago, Bonnington Falls was created and stopped the Sockeye Salmon from reaching their breeding grounds. This also left some sockeye salmon trapped in Kootenay lake and unable to return back to the ocean. Over the years, the smaller sockeye trapped in Kootenay lake survived because the lakes do not produce enough nutrients (food) for a large Sockeye . 15,000 years later, those smaller sockeye salmon are what we know as Kokanee salmon (salmon that have adapted to living in fresh water).
Kokanee salmon are native to British Columbia, Alaska, Washington, Idaho, Russia and Japan.
The Experiment
1. Set aside one bowl to represent the ocean and one (smaller) bowl to be the freshwater lake.
2. Gather together the different beads that will represent the different sizes of Sockeye. For example - a (gold) larger size bead to represent larger sockeye and smaller silver beads for smaller sockeye.
3. Add 4 beads of both types to the ‘ocean’ bowl.
4. As the Sockeye salmon migrate upstream to spawn, take 2 large Sockeye and 2 small Sockeye from the ocean, and put them into the freshwater bowl. Now double the number of salmon in the freshwater bowl to represent their offspring.
5. Add some more large beads to the ocean bowl to show that the larger, stronger salmon have a better chance of survival in the ocean.
6. Imagine that a dam is created between the two bodies of water and the salmon (of both sizes) are now landlocked in the freshwater for their whole lives.
7. Add more small sockeye (silver beads) to the freshwater bowl to demonstrate that the smaller salmon are adapting to survive in the freshwater lake. Add more large sockeye to the ocean to demonstrate they are continuing to thrive in the ocean.
8. Take away more large beads from the freshwater and also remove more smaller silver beads from the ocean. This is to express that now the salmon are adapting to their final habitat.
9. In the end, you should have one bowl (the ocean) with only Sockeye Salmon (larger gold beads) remaining, and one bowl (the fresh water) filled with only Kokanee Salmon (smaller silver beads).
Additional Information:
Natural selection occurs when one organism is better adapted to their environment, and therefore tends to survive and produce more offspring. This is exactly what happened with the Kokanee salmon in freshwater lakes.
If the Kokanee and Sockeye salmon populations are separated for up to 15,000 years, they may continue to diverge and become completely different species that can no longer mate. This is one mechanism of how new species evolve.
