The purpose of this lab was to observe the opening of the fishs mouth and its operculum (flap covering the gills) to determine the breathing rate of fish at different temperatures.

WE EXPECT THAT AS THE TEMPERATURE INCREASES THE BREATHING RATE WILL INCREASE.

Independent Variable: Breathing rate

Dependant Variable: Change In water temperature

Controlled Variable: Size of container and bowl, number of Gold Fish

Preparation:

1. Prepare test tank by filling a one liter jar half full with water from the aquarium.
2. Use a fishnet to transfer the smallest fish from the aquarium to the jar. Record any characteristics so it can be identified easily.
3. Wait about 5 minutes to allow the fish to calm. Remain cautious as the experiment proceeds.
4. Find the fish’s mouth and operculum.
5. Count the number of times that fish 1 opens and closes its mouth and operculum over a period of 1 minute. Use a timer to do this.
6. Repeat step 5 three times.
7. Average the three trials to determine the average breathing rate for one minute.

Testing how temperature affects breathing rate…

1. Place thermometer inside the container.
2. Set the container in a half filled bowl of water.
3. Lower the temperature of the water in the container by five degree intervals by adding pieces of ice to the water in the bowl.
4. At each uniform temperature, make sure to wait 5 minutes to allow the fish to get used to the new temperature.
5. Count the number of times the fish opens and closes its mouth in a minute. Do this three times for each temperature.
6. Continue lowering the temperature by 5 degree intervals but make sure you don’t go below 5 degrees.
7. Repeat this process for each fish.

A fish can be said to breathe when it forces water across its gill filaments. During

breathing a fish opens its mouth and closes its operculum. The fish then closes its

mouth, contracts its pharynx, and opens its operculum. This forces water over the gill

filaments. As water passes over the gill filaments oxygen diffuses into the capillaries

of each filament and carbon dioxide diffuses out. After passing over the gills, water

leaves the fish through the open operculum. Thus the opening and closing of the mouth

or the operculum can be used to measure breathing rate.

1 liter container

1liter bowl

Ice

3 gold fish

Thermometer

Stopwatch

Fish tank with water pump and water plants

Our hypothesis was that the breathing rate of the fish would increase as the temperature of the water increased. The results indicate the hypothesis should be accepted.

   The increase in breathing rate most likely relates to the increase in metabolism when the temperature rises. This is why other cold blooded animals such as lizards are still when it’s cold but are very active when it’ warm. Also gases tend to dissolve into liquids easily when its cold compared to when it’s warm. So the fish must breath more when it’ warm to obtain enough oxygen.

   This experiment could have been used to test breathing rates of different kind and size of fish. The temperature would have to be controlled in that case.

   Although counting keeping up with the opening and closing of the fish’s mouth was difficult, the experiment went smoothly overall.