Students who demonstrate understanding can:
3-LS4-3. Construct an argument with evidence that in a particular habitat some organisms can survive well, some survive less well, and some cannot survive at all.
Prepare science notebooks with a Velocity Datasheet.
Find a stream location where the stream bank is low and level and students can spread out along it without trampling vegetation. Choose the length you would like students to measure (e.g., 10 feet, 20 feet, 25 feet) based on the bank and channel characteristics. Avoid stream stretches where the rubber ducky might run into rocks or snags.
Ideally, you need at least 6 students to take measurements, one of whom has waterproof boots that won’t be overtopped by the stream. If you have additional students in your group, they can rotate the roles. The activity can also be done with only three students.
Set-up with six students:
(With only three students, one would drop the rubber ducky while holding one end of the string, rope, or the measuring tape; another would catch it while holding the other end, and a third one would be the timer and recorder.)
Procedure
V= D/T
Velocity = Distance / Time
Ask students to tell you why salmon need water that is “not too slow and not too fast.”
Draw their attention to the question on their data sheet or in their science notebook:
Based on your results, could salmon survive well in our stream? Yes or No & Why?
If you have time, have a discussion about how they would answer this question. Ask students to explain their answers by providing evidence to answer the “Why?” If there isn’t enough time for this discussion during the field trip, tell them to write their answers when they’re back in their classroom.
This field trip activity was developed for the Anchorage School District Watershed Education Program. The field trip program supplements a 4th grade STEM Kit on the theme of Interdependence and a focus on Anchorage watersheds and salmon.
Significance of Water Velocity for Salmon
Salmon require stream habitats where water velocities that provide enough turbulence to mix oxygen from the atmosphere into the water column but which are not too swift or turbulent too require fry and juveniles to expend energy to avoid being washed downstream from areas where they can find food. Coho salmon juveniles who spend up to three years in streams require velocities less than 1 foot/second. Different species of adult salmon vary in terms of their swimming abilities although some like cohos who move far up streams to spawn can swim against currents of 10 feet/second.
Measuring water velocities is a relatively simple sampling exercise, requiring only an object that can be observed and timed as it’s carried by the current. The accuracy of the measurement is limited, however, by taking the measurement at or near the surface of the stream since water velocities vary considerably throughout the water column and smaller fish and other animals are adapted to seek shelter from high velocities in a variety of ways.
Possible Learner Misconception(s) and Instructional Clarifications:
Learning Misconception: If the velocities are too high in the main channel of a stream, young salmon will be washed downstream.
Instructional Clarification: Salmon can live in stream stretches with high velocities through their adaptation of staying behind logs and rocks or near the bottom or under banks, and then darting out into faster water to find prey.
Learner Misconception: The macroinvertebrates that salmon depend on for food can’t survive in stream stretches with strong currents.
Instructional Clarification: Not all animals are as vulnerable to high velocities as juvenile salmon and salmon eggs and alevins. Some macroinvertebrate species (for example, black fly larvae) have adaptations to attach themselves to the bottom of rocks.
Engaging in Argument from Evidence
Construct an argument with evidence.
LS4.C: Adaptation
For any particular environment, some kinds of organisms survive well, some survive less well, and some cannot survive at all.
Cause and Effect
Cause and effect relationships are routinely identified and used to explain change.