A Little Bit More
We rarely think of temperature as being an important factor that determines where a fish lives, but it is. If you raise tropical fish, you may already know that they need to be kept on the warm side so you’re aware of this issue. However, I think it’s a little bit more difficult for us to think of a fish needing to be kept cooler, rather than warmer, to be healthy but it’s true. Keep in mind that fish are ectotherms (body temp is same as environment) so they are very much at the “mercy” of surrounding waters whether they’re too warm or too cold. Don’t get the impression that ALL trout have the same temperature requirements but they are all much more alike as a group – need cold, well-oxygenated waters - than many other kinds of fishes.
Here’s a limited account of the water temperature preferences of some familiar fishes as well as temperature levels that are considered lethal for them.
Species Best Temp Lethal Temp
Rainbow Trout 19°C (66°F) 26°C (79°F)Brook Trout 15°C (59°F) 26°C (79°F)
Brown Trout 16°C (61°F) 29°C (84°F)
Lake Trout 10°C (50°F) 26°C (79°F)
Bass 18°C (64°F)-25°C (77°F) 32°C (90°F)
Catfish 19°C (66°F)-29°C(84°F) 32°C (90°F)
Sunfish 19°C (66°F)-27°C(81°F) 32°C (90°F)
Activities
Science & Math – Take My Temperature
Objectives: Better sense of local water temperatures
Materials: Floating thermometer, string and weight, and notebook/pencil
It’s quite likely that you and your students have no clue what the water temperature of the local pond, stream or lake is. Naturally, this will vary over the course of a year, but it’s still worthwhile to get a feel for water temp in your local area. Here’s an opportunity for you to find out. If you don’t have any natural water around your school, place several containers of water in different locations (shaded vs. sunny) around the school and after a day, see what the temp is for these. You might want to discuss with students the difference between monitoring small containers of water vs. natural bodies of water if you go this route.
Using a floating aquarium thermometer, weight and string, you should be able to find out the surface and deeper water (maybe a foot or two beneath the surface) temperatures of your local water.
1. Float a thermometer in the water for 10 minutes and then read the temperature. Be sure to note the date, time, and temperature in a notebook so you can keep a record over time of any changes that may occur.
2. Using the same or similar thermometer, tie a string around the instrument, weigh it so it won’t float and allow it to sink several feet (you determine how deep you want to monitor) into the water. Allow another 10minutes there and then quickly raise and register the temperature at the deeper location (date, time, and temperature along with depth)
3. You can do this as often as you wish – maybe once a week, every other week, once a month, you decide.
4. After you’ve accumulated enough data for your purposes, have the students record their data on a graph showing time of year and surface and deep water temperatures. You may find that the temp is reasonably consistent over time or may find it varies quite a bit. Furthermore, you may find the temp on the surface and deeper water varies differently over time.
5. If you compare the temperatures of your local waters with the acceptable temperatures of the fish we’ve shared, taking into consideration the time of year, you have a good idea whether trout are likely to live near you. Keep in mind that different bodies of water may vary a great deal in temperature (shallow lake, small stream, stagnant pond, deep lake, or large river). This should also make for some interesting discussion about why the different temperatures in the different locations.
Question: You can ask students to predict where they think fish would be found at different times of the year based on their temperature preferences. On a hot summer’s day, fish in your local pond would probably be deeper in the water while on a cool spring day, they might be close to the surface. Fish can and do interpret water temperatures and move where they feel most “comfortable”.
Key Concepts
Adaptations and Diversity, Environmental Issues, Populations and Ecosystems
Questions
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