The following is the reply I received from Douglas Coughran one of Western Australia's leading whale experts.
"The image you took of this whale's skin condition is very important from a documentation point of view. Nationally this type of skin lesion was first noticed in the East Coast population a few years back and then it made an appearance in the West Coast population soon after. The skin lesion has not yet been biopsied to establish exactly what is going on with the effected whales. So any more you see, please send some images onto me and it will help me work on it some more thanks Paul. By all means you can do a small update for your web page to keep people informed. I don't think it is a big issue for the whole population but certainly is for those effected. Then again, unless we keep a watch over the population we may miss "the canary in the mine".