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How might salmon use the Sun and visual clues to navigate?

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A herd of wildebeest, including calves, moves across a dusty savanna in Africa with scattered trees visible in the background. — Migration A herd of common wildebeest (*Connochaetes taurinus*) migrating across a dusty savanna in Africa. The animal is a keystone species (i.e., a species with a disproportionately large effect on its biological community) in plains and acacia savanna ecosystems from southeastern Africa to central Kenya.

While it is widely presumed that salmon utilize the Sun for navigation during their migrations, the specific mechanisms remain a subject of scientific study rather than established fact.12

Navigation and the Sun

It is hypothesized that salmon use the Sun as a celestial compass to plot their course, similar to other migratory animals. However, navigating by the Sun is significantly more challenging for fish than for birds because light rays behave differently when passing through water, making it difficult to localize the Sun’s position accurately. While some experiments suggest that salmon may rely on geomagnetic orientation or the Sun's position to reach their general home stream system, these methods are not fully understood.12

Visual and Topographical Clues

Beyond celestial cues, salmon and other fish rely heavily on visual and topographical landmarks to recognize their range and spawning grounds. These visual bearings are considered to have great importance for orientation. Once salmon reach their home stream system, however, their navigation shifts from these long-range cues to a reliance on olfaction, using a learned chemical signature to identify their specific natal stream.1324