John,
Yellow grubs are common, especially in weed infested, clear water.
The primary hosts are snails. The parasite releases from snails, swim, then attach to fish, usually near a fin. The parasite forms a cyst, and go through their metamorphosis. Then, they go through another free swimming phase, back to snails.
Are they trouble? No. Unsightly and unpalatable to people? Yes.
Stock redear sunfish...they eat snails. And, manage your vegetation. Some vegetation is good, too much can cause numerous problems, yellow grubs being one of them.

Teach a man to grow fish...
He can teach to catch fish...