Hi Toptex,
Are you using fridging in conjunction with the salt baths? Fridging will help inhibit the fungus from spreading, and aid Jim in fighting off the infection.
What concentration of salt are you using in the salt baths (ie. how many teaspoons per litre of water?).
Also, how long are you leaving Jim in the salt bath solution? If the salt concentration is too strong, or Jim is left in the bath for too long (ie. over ten minutes), the salt can cause the gills to erode, and bleed.
And, how many times a day are you salt bathing Jim? (sorry to be the nag, but the more information you can give us, the better we can help).
Has Jim shown any signs of distress while being salt bathed?
Tackling fungal infections is a game of patience. Even with fridging and salt baths, it can take weeks to get rid of it.
Other than the fungus on the gills, Jim actually looks okay. He is nice and plumpish - which means he can stand going without food for a time while being fridged (if not already in there, I think this will be the best place for him).