Stlhdh2o -
The guys are right. For salmon jacks are mature males that have returned at an younger age than normal for the species. They are capable of spawning and do contribute to the gene pool of the population. Salmon jacks are typically found in greater abundance in rivers than normal because marine water fisheries (sport and commerical) catch the larger maturing adult fish and not the jacks.

The situation with the anadromous trout (steelhead, cutthroat and Dolly Varden/bull trout) is a little different. With steelhead true jacks are found; returning after just one summer of feeding. Rarely a early maturing steelhead females - Jills are found. In South Oregon and Northern California steelhead half pounders are found. These are immature fish that return to the river, spend the late fall, winter in freshwater and then return to the ocean without spawning to return later. Steelhead with this life-history are rarely found in Washington waters.

With the cutthroat and Dolly Varden/bull trout typically behave like half pounders and spend that first winter after smolting back in freshwater as non-spawning fish - sometimes called subadults. With these fish there are lots of exceptions to the "rules".

Tight lines
Smalma