Salmon Find the Way Home

Written by Studio AM.

Many salmon leave freshwater as young fish and spend part of their lives at sea. When they are ready to reproduce, they often return to the river system where they hatched. This return journey involves more than one kind of clue.

Research suggests that salmon can use Earth's magnetic field during ocean navigation. The field varies across places, providing information that may help them reach the right coastal region. That broad guide is different from identifying a particular stream.

Smell is important near home. Young salmon learn odours associated with their river. Returning adults can use these chemical cues when choosing between waterways, including at a junction where streams meet. Not every fish returns to its original site; some enter other rivers.

For many Pacific salmon, spawning is followed by death. Their bodies bring nutrients from the sea into freshwater habitats. Animals such as bears carry some fish onto land, and the nutrients can reach nearby plants. Studies of nitrogen in leaves have helped researchers trace this connection between the ocean, salmon and riverside forests.

Questions

Choose an answer. The explanation appears after you answer.

  1. Question 1 of 4

    What is the passage mainly about?

  2. Question 2 of 4

    Which clue helps returning salmon recognise waterways near home?

  3. Question 3 of 4

    If familiar stream odours became harder to detect, which part of the journey might become more difficult?

  4. Question 4 of 4

    In this passage, "junction" means

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