Why do salmon swim upstream?
Show answer & explanation
Answer: Spawning in birthplace
Escaping ocean predators — Wrong. Ocean has predators, but upstream migration is for reproduction—returning to natal streams to spawn.
Spawning in birthplace ✓ — Correct! Natal homing! Salmon return to birthplace to spawn: (1) Imprinting—remember birth stream's chemical signature. (2) Olfactory navigation—follow scent upstream. (3) best conditions—gravel beds for eggs. Incredible journey: hundreds of miles, swimming against current, jumping waterfalls. Anadromous life cycle—born in freshwater, mature in ocean, return to spawn. Most Pacific salmon die after spawning (semelparous). Exhausting migration—use all energy reserves. Magnetic sense aids ocean navigation!
Searching for more food — Wrong. Salmon don't feed during spawning migration—use stored energy. Upstream journey is reproduction-driven, not foraging.
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