There are five species of salmon that spawn in Washington state: Chinook (aka King), pink, Coho, chum, and sockeye. All five are an important part of the ecosystem, but Chinook are an especially important part of the Puget Sound's food chain as they are the primary food source for the critically endangered Southern Resident Orca population. While the orcas will also feed on Coho and chum salmon, as well as some other fish, the Chinook is the variety of salmon that these beautiful creatures rely on the most.
Salmon are an example of anadromous fish - that is, fish who use freshwater environments for spawning and reproduction and saltwater for feeding and growing as adults. After salmon hatch and develop into fry, they will slowly begin making their way downstream towards the ocean, where they will mature into adults. Salmon return to the stream where they're spawned as an efficiency measure - after all, why waste time and energy looking for a safe place to spawn when you know where one is from your own birth? Scientists believe that salmon can tell directions in the ocean by the earth's magnetic field acting like a compass. When they find the river they came from they start using their sense of smell, which is stronger than that of a dog or a bear, to find their way back to their home stream. They build their "smell memory-bank" when they start migrating to the ocean as young fish.
This amazing migration takes place every year, and here in Seattle Southside we're lucky enough to be surrounded by great places to see the salmon.