In 2015/16 two Honours projects, one in IMAS and one in Chemistry, investigated the possible causes of the melanisation.  Zinc levels were higher in the muscle of melanised fish and has well known association with melanin in other animals. No parasites were present in the muscle of the affected fish. A journal article from those projects is available here.

In 2018/19, in another IMAS Honours project recreational fishers were surveyed to assess the extent of muscle melanisation in marine fish in Tasmania. The vast majority of respondents indicated that they had observed melanisation in at least some of the sand flathead they had caught. The findings of this survey can be found here.

That Honours project included studies of other aspects of melanisation, confirming that the melanisation of flathead muscle was most severe in Deceitful Cove, Tamar Estuary.  It was suggested that both eumelanin and pheomelanin were involved in this phenomenon.  Melanisation was not, however, related to fish condition, age, sex, maturation stage, fish weight, fish length or size of melano-macrophage centres in the liver or spleen. A journal article about this project is available here.

Muscle melanisation in sand flathead is currently the subject of an ongoing PhD research in the School of Natural Sciences (Chemistry) and IMAS, University of Tasmania.

A list of published reports about fish health and melanisation in general is available at this here.