Range of Tolerance
Graphing Activity
Name:______________________________________Date:__________Hour:____
Steelhead trout, otherwise known as rainbow trout, have seen a population decline in the Western
United States over the last decades. There are a wide variety of conditions that are threatening the
population, including pollution, climate change, and invasive species. This activity will look at the effects
of varying two specific abiotic factors on a controlled population of trout.
Graph the range of tolerance data below for steelhead trout. Water temperature is the independent
variable for graph 1 and dissolved oxygen is the independent variable for graph 2, these should be
graphed on the x-axis. The number of fish, the dependent variable, should be graphed on the y-axis.
Graph 1
1. Label the optimal range on the graph. This is the amount of an abiotic factor that produces the
highest possible population. For water temperature, this would be about 6-10°C.
2. Label the zone of physiological stress on the graph. This occurs when an abiotic factor exists
at levels that are too high or low to support normal biotic potential. This would be 3-5°C and 11-
16°C.
3. Label the zone of intolerance on the graph. This occurs when a population is absent (or in this
case, nearly absent). This occurs at either extreme of our water temperature graph, below 3°C
and above 16°C.
Water
Temp
(°C)
Number
of
Fish
0
0
1
1
2
2
3
5
4
7
5
10
6
15
7
21
8
24
9
20
10
17
11
14
12
12
13
10
14
8
15
5
16
3
17
2
18
1
19
1
20
0
