Sockeye Salmon are plankton feeders, which gives them a delicious flavor and prevents them from accumulating mercury as much as the more predatory salmon.  They are common in the northern parts of the pacific ocean.  Sockeyes are very tough to fish for, but fresh-run sockeyes will often take a woolly bugger.  In Alaska, we found rivers full of Sockeye Salmon at the peak of their spawning runs.  Hundreds of fish would be stacked in a small hole, slowly circling around and milling about.  The brighter, fresher fish were willing to take a fly if presented right in their face.  Comets, Egg-sucking leeches and wooly buggers produced. 

Appearance varies greatly depending on how long the fish have been in fresh water. This fish was still pretty bright silver. As they darken and become red, their flesh softens and eventually decays.