Thanx Concerned Angler for the info. That's what I was looking for.
It turns out the critter we are dealing with is a microorganism caled Henneguya salminicola. It can be found in all Pacific Salmon but I have seen it most in Sockeye. There is no mention of health risk to humans though they certainly affect the appearance and perhaps taste of the fish. I cut 'em out.
I found an excellent paper on the web that was written by Stone, MacDiarmond and Pharo for the government of New Zealand. A couple of short excerpts are below. Here's a link if anyone's interested (page 168)
http://www.maf.govt.nz/biosecurity/pests-diseases/animals/risk/salmonids-ra.pdf
H. salminicola produces cysts in the muscle of infected fish. The cysts vary from 4-15 mm in diameter, and are filled with masses of spores and debris of destroyed muscle. The cyst wall is host connective tissue resulting from the host’s immune system’s attempts to isolate the parasite. Cysts contain proteases which probably
function to breakdown host tissues for parasite metabolism. After death, these proteases are released into the flesh.
Salmon are infected during their first 6 months in freshwater, and prevalence increases over the whole rearing period. H. salminicola distribution may be related to areas where carcasses of spawned adults accumulate and decompose.
Apologies for the long winded post, I haven't found anybody who knew about this before so maybe you folks will find it useful.
Tight lines, Rustle