Yeah, sorry the pic isn't any better..
Something you can do is mix a bucket of pond water with stock salt-straight NACL-in maximum dissolved concentration and put fish in that solution for several minutes. I think what you have is anchor worms, common external parasite in a stressed fish. You can take small tweezers and remove them manually, they are just like a short (3/16-1/4") piece of monofilament fishing line, but hard like a micro piece of "stick". The head is "T" shaped and anchors just under skin-usually under a scale-and the body, or "stick" part of parasite is normally pointed aft or slightly down, a little hard to see but you can grab that stick with fingernail or tweezers and pop it out.
There is no cure for removing these from a pond but the healthier the fish the less chance there is of attachment.
If you salt dunk these fish, when you put them in the salt solution you may see the fish go into what appears to be a convulsive behavior, this is normal, it won't kill the fish and the fish may even go belly-up but leave it in there for 2-4 minutes then remove the fish and put into straight pond water in another bucket and it will right itself fairly quickly. This salt solution will literally burn the eggs, interrupting the reproductive cycle of the parasite.
This procedure works for any external parasite including anything attached to gills.
There are some species that react differently than others in this salt solution but we use this on LMB, SMB, BG, WAE, GSF and RES.
I recently treated some YP with the same mix and had no mortality in 40+ fish. I can't say how any other species react other than CC, they turn pale in seconds and can only be in this for maybe 30 seconds before the burn is irreversible-they don't handle this well but they are also non scaled.

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