Aquatic Respiration Project
Have you ever sat down and watched fish in a tank or in a pond? Did you ever watch how the fish breathes? We, often call the flaps on either side of the head, gills, but those aren’t really the gills at all; they’re operculum. The gills are actually underneath those flaps and are responsible for pulling the oxygen out of the water so that the fish can breathe! When a fish opens its mouth, it pulls the water into its body and expresses that water through the gills and out of the “vents” called the operculum. The gills take the oxygen out of the water and spread it through the fish’s body so that it can survive underwater. Just like us, the fish breathes out carbon dioxide so when the fish exhales, that’s what goes back into the water. Fascinating!
What you’ll be doing for this experiment is determining whether or not a fish’s respiration changes in response to changes in its environment.
How Do Fish Breathe Underwater?
Items that you will need:
2 (two) identical fish containers or bowls
2 (two) goldfish. One large goldfish and one smaller goldfish. (Please make sure, before you buy any fish that you are prepared to keep them or find them a good home.)
1 (one) large plastic bowl (clear)
2 (two) 1/2 cup measuring cups
Directions for Project:
1. Fill the goldfish bowls with lukewarm water. (or desired temperature for your species of fish)
2. Place one fish each into the two identical bowls.
3. Start with the smaller fish. Set your stopwatch for 1 minute. Count the number of times you see the small fish breath within that minute. It’s important to be as consistent as possible so choose one of the two ways to watch how many times the fish breathes in one minute. You can either count how many times the fish opens its mouth or count each flap of the operculum. Do this three times and calculate the average. Write down the number of breaths.
4. Repeat step 3 for the larger fish.
5. For the next step, add the proper amount of water conditioner in half of a cup of water and pour the mixture into the bowl of the small fish. Set your stopwatch for one minute and count how many breaths the fish takes. Write down the number of breaths as well as any behavioral change.
6. Repeat process with the larger fish.
7. Fill up the large clear container with cold water. Place the fishbowl inside the cold water. (set the fishbowl itself into the container of water. Don’t mix the water from the large container and the fishbowl. Do not empty the fishbowl into the large container.)
8. Using a thermometer, take the temperature of the water that’s inside the large container and write it down.
9. Add ice cubes to the large container.
10. Again, count the fish’s breathing, per minute, until the temperature on the thermometer stops changing.
11. Repeat the process with the larger fish. (remember to replace the water inside the large container with more cold water.)
12. On a line graph, chart your findings. Use the horizontal line should be the number of times that the fish breathes per minute and the vertical line should indicate the temperature of the water.
Is there a connection between the fish’s breathing rate and the temperature of the water?
Fish breathe more when they are in warm water. Their breathing slows down when the water is colder. Fish also breathe faster when they are scared or excited. A smaller fish breathes more times per minute than a larger fish.