Question

Task #1: Respiration Rate Changes in Minnows as a Function of External Temperature (adapted from exercise developed by Daphne McKay)

Introduction

Counting gill cover movements is a way to calculate respiration rates in fish. Fish

breathe by taking water in through the mouth and forcing it over the gills when the mouth

closes. An oxygen-carbon dioxide exchange occurs. Then the operculum opens to allow

the carbon dioxide-rich water to exit. The respiration rate changes in response to changes in the water temperature. An increase in the water temperature increases the fish respiration rate as the amount of dissolved oxygen decreases. On the other hand, a decrease in the water temperature decreases the fish respiration rate as the amount of dissolved oxygen increases.

Purpose

To determine what effect a change in water temperature has on the rate of respiration in fish.

Objectives

Students will record the effect of temperature on the respiratory rate in minnows.

Students will represent their finding by graphing the results from the experiment.

Procedure

Gently remove a fish from the tank and place it in a Ziploc bag that is half filled with water from the tank that held the fish. Be careful while handling the fish throughout the activity to avoid injuring them.

Place the Ziploc bag containing the fish in a larger container that is half full of water at room temperature. Place athermometer in the Ziploc bag. Record the temperature of the water. Count and record the number of times the operculum closes in one minute. Before each count be sure to let the fish adjust for a few minutes. Repeat twice, recording the data for each trial.

Slowly add ice to the water in the larger container until the temperature is 10 degrees below the starting room temperature. Wait for the temperature in the Ziploc bag to reach 10 degrees below room temperature. Note that the temperature changes should not go above or below ten degrees Celsius from room temperature since this could result in physiological shock to the fish. Count and record the number of times the operculum closes in one minute. Repeat twice, recording the data for each trial.

Pour off some of the cold water and slowly add hot water to the larger container until the temperature has reached 10 degrees above the starting room temperature. Do not allow the water temperature to exceed 35 degrees Celsius. Record the temperature and operculum closings for one minute. Repeat twice, recording the data for each trial.

Return your fish to the tank.

Calculate the average number of operculum movements for each of the 3 different water temperature trials.

Results

Table 1: Number of Operculum Movements per Minute in Different Temperature Water (5 pts.)

Temperature in Celsius degrees	Number of operculum movements/min (1st trial)	Number of operculum movements/min (2nd trial)	Number of operculum movements/min (3rd trial)	Average number of operculum movements/min
Start temperature in Celsius degrees
Temperature 10 degrees below start
Temperature 10 degrees above start

Graph

Use your data to construct a graph showing the relationship between temperature and respiration in minnows. (5 pts.)

Answer 1

Temperature in Celsius degrees	Number of operculum movements/min (1st trial)	Number of operculum movements/min (2nd trial)	Number of operculum movements/min (3rd trial)	Average number of operculum movements/min
Start temperature in Celsius degrees	30	27	29	28.66
Temperature 10 degrees below start	25	24	22	23.66
Temperature 10 degrees above start	33	35	40	36