When Will Our Salmon Hatch?

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Objective

SWBAT predict when the salmon eggs will hatch based on water temperature.

Big Idea

Salmon eggs hatch according to a predictable schedule.

Warm Up

15 minutes

My class participates in the salmon in the classroom program. As a part of this program we receive approximately 250 eyed eggs each winter. The eyed eggs are kept in the class tank. The tank is wrapped in black paper to restrict the amount of light exposure. The students raise the salmon until they are large and strong enough to be released into the local stream ecosystem. 

When the salmon first arrive, I provide each student with time to observe the eyed eggs in their tank. In order to do so, I create a small observation window in the tank's paper covering. I ask each student to record their observations in their salmon journal. A completed observation from a student's science journal can found here and a video of two students explaining their observations can be found here also show the salmon video which explains the spawning process at the hatchery where our salmon were spawned. We continue to observe and record information about their salmon from the date of their arrival until their release date.

 

Guided Practice

20 minutes

I then guide students in completing the when will they hatch activity. Because this activity requires students to read complex text and use math skills, I place this worksheet on the document camera and guide students through each step of the process. Precision is crucial in this activity, so I guide students through every step and check to ensure that each student has the correct answer before moving on to the next step.  A sample of a student's completed work can be found here.

In this activity, students compute daily temperature units for the salmon eggs. Salmon eggs require a certain number of temperature units to hatch. Knowing the eggs' fertilization date, water temperature at the hatchery, and water temperature in our class tank, we can predict a range of time in which the eggs will hatch.

As a teacher, this information is important. I check the tank daily during the expected hatching period. Eggs that do not hatch need to be removed from the tank so they do not contaminate the water. Also, once all of the eggs have hatched, the paper can be removed from the tank as the alevin are not as sensitive to light. Once the eggs have hatched, the alevin need to be closely observed to ensure that you start feeding them as soon as the buttoning up process is complete. (Salmon fry are very hungry!)

Closing

90 minutes

Even though our formal study of salmon concludes with this lesson, we continue to observe the salmon in our classroom tank as they grow and develop. Later, in the spring, I take the students on a salmon release field trip as a culminating activity for our unit of study. We walk to the local stream site to release the salmon that we have raised. On the field trip, the students record their thinking on the salmon release journal. Please see the reflection section for additional information on planning a salmon release field trip.