Experiment 1: Analyze Stickleback Fish from Lakes

Part 2: Scoring the Fish

Now that you have stained the fish, you will categorize each specimen according to whether it has a complete, reduced, or absent pelvis, much like you did in the first tutorial.

Click here if you need a refresher on the scoring system.

In this experiment, you will score 20 fish from Bear Paw Lake and 20 fish from Frog Lake. These two lakes have the same river drainage to the ocean, which means that they were probably populated by the same sea-run population of threespine stickleback at the end of the last ice age. However, these lakes provide distinct environments for their resident sticklebacks—in particular, one lake contains large fish, such as the trout, that prey on stickleback, and the other lake lacks large predatory fish.

Watch this video to learn about the freshwater
stickleback populations in Bear Paw and Frog lakes.

The 40 specimens you will analyze were selected randomly from a much larger sample of fish collected from these lakes by Drs. Michael A. Bell and Peter J. Park. Thus, the data you will obtain are representative of the population as a whole.

Click here to read more about the importance of random sampling.

As you start the experiment, the pelvic scores will appear in a chart in this window.