Pink salmon or humpback salmon, Oncorhynchus gorbuscha, is a species of anadromous fish in the salmon family. It is the smallest and most abundant of the Pacific salmon. In the ocean, pink salmon are bright silver fish. After returning to their spawning streams, their coloring changes to pale grey on the back with yellowish-white belly (although some turn an overall dull green color). As with all salmon, in addition to the dorsal fin, they also have an adipose fin. The fish is characterized by a white mouth with black gums, no teeth on the tongue, large oval-shaped black spots on the back, a v-shaped tail, and an anal fin with 13-17 soft rays. During their spawning migration, males develop a pronounced humped back, hence their nickname “humpies”. Pink salmon average 4.8 pounds (2.2 kg) in weight. The maximum recorded size was 30 inches (76 cm) and 15 pounds (6.8 kg). Pink salmon are coldwater fish with a preferred temperature range of 5.6 to 14.6°C, an optimal temperature of 10.1°C, and an upper incipient lethal temperature of 25.8°C. The species is native to Pacific and Arctic coastal waters from the Sacramento River in northern California to the Mackenzie River in Canada; and in the west from the Lena River in Siberia to Korea. Populations in Asia occur as far south as Honshu in Japan. Pink salmon were introduced into the Great Lakes and in Iran. The pink salmon is critically imperiled in California, and imperiled in Washington. In Alaska and British Columbia, they are secure.