Pink salmon rarely travel far upriver to spawn; they are typically found in shorter coastal streams. When the fry emerge from the gravel, they already have the silvery color of smolts, and they migrate directly to sea. Pinks spend a fixed 18 months at sea; thus, all returning pink salmon were born in the same year, and different year classes do not interbreed.
Pinks average 2 to 5 pounds. Sea run pinks are easily distinguished by the large oval spots on their backs and tail fins. Spawning males develop a large hump on their backs, earning the species its other name, “humpback.” Some biologists think the males’ conspicuous hump diverts the attention of predators away from the females.