Don't think it's "Ich".... which shows as small white dots/pimples...
Looks more like "Red Spot".... which is not good news....
Known disease in Silver Perch and Barramundi... but couldn't find anything specific about Jade Perch...
Fungal disease... often triggered by acid rain/high rainfalls....and sibsequently declining water quality (low salinity, low pH, high organic load)...
http://www.dpi.nsw.gov.au/__data/assets ... Manual.pdf(see page 40 in the above link)
and...
http://library.enaca.org/Health/FieldGu ... ndrome.pdfKnown to cause mass mortalities... suggested treatments are "formalin"... bit beyond the average AP'er...
Or 10ppt salt baths.... see the first link page 41...