Sounds like this might be the thing, from ifish.net...
Re: Tapioca Disease in Salmon
Here's the scoop on those parasites:
Henneguya spp.
This myxozoan parasite forms small white or yellow cysts about the size of a grain of rice in the flesh of marine fishes like salmon, rockfish, and flatfish. These usually do not affect the flavor, texture, or safety of the meat, but one species H. salmonicola may produce visible cysts filled with milky fluid in coho and sockeye salmon, reducing the attractiveness of the flesh. However, this is not a common problem.
Kudoa spp.
Myxozoan parasites of the genus Kudoa form white cysts in the muscle of salmon and many other local marine fishes. The frequency of this problem is very low in wild-caught salmon. The cysts may be large enough to form noticeable white patches or streaks in the meat. After the death of the fish, the parasites release an enzyme that breaks down muscle tissue and causes the flesh to become soft and less desireable as food. The enzyme is fairly heat-stable and may continue to breakdown tissue even if the meat is smoked.
Buck, it sounds like yours was a case of H. salmonicola or what has commonly become known as "tapioca disease". Here's a photo from the PP board that is probably a case of the Kudoa species variety:
