A「fish」that must「travel to higher ground in order to spawn」from sea level to far upstream in freshwater rivers:「Chinook and sockeye salmon from central Idaho, for example, travel over 900 miles (1,400 km) and climb nearly 7,000 feet (2,100 m) from the Pacific Ocean as they return to spawn. …Typically, salmon are anadromous: they are born in fresh water, migrate to the ocean, then return to fresh water to reproduce. However, populations of several species are restricted to fresh water through their lives. Folklore has it that the fish return to the exact spot where they were born to spawn. Tracking studies have shown this to be true, and this homing behavior has been shown to depend on olfactory memory.」
　　[　https://en.wikipedia.org/wiki/Salmon 2013-08-27　]　…In other words, they find their natal home by honing in on the smell of the place, not unlike a「fish with a butt plug.」'salmon' in English means 'leaping' that is another reference to a「fish with butt plug.」
　「Fish that builds the soil.」…trees that line salmon run rivers grow 30% faster than adjacent trees slightly farther from the water:「Grizzly bears function as ecosystem engineers, capturing salmon and carrying them into adjacent wooded areas. There they deposit nutrient-rich urine and faeces and partially eaten carcasses. Bears are estimated to leave up to half the salmon they harvest on the forest floor, in densities that can reach 4,000 kilograms per hectare, providing as much as 24% of the total nitrogen available to the riparian woodlands. The foliage of spruce trees up to 500 m (1,600 ft) from a stream where grizzlies fish salmon have been found to contain nitrogen originating from fished salmon.」
　　[　https://en.wikipedia.org/wiki/Salmon 2013-08-27　]　
　Salmon also「seal themselves internally like a butt plug」:「…the myxozoan parasite Henneguya salminicola is commonly found in the flesh of salmonids. It has been recorded in the field samples of salmon returning to the Queen Charlotte Islands. The fish responds by walling off the parasitic infection into a number of cysts that contain milky fluid. This fluid is an accumulation of a large number of parasites.」
　　[　https://en.wikipedia.org/wiki/Salmon 2013-08-27　]　

Modern definitions (that generally disregard history) …excluding politically incorrect concepts and other meanings deemed offensive today; may list only pigeonholed definitions, euphemisms, or meaningless mnemonics)
Chinese: trout; salmon
Japanese: salmon, chum salmon
Unihan extended: salmon; spheroides vermicularis
EDRDG: salmon