Gladstone Fish Health Investigation 2011 - 2012 - Western Basin ...

Laboratory testing Phase 1Seven river jewfish and one ghost grinner were submitted to Biosecurity Queensland inDecember 2011 from Port Curtis where they were collected floating on the surface inresponse to a report of a fish kill. Chemical residue testing and pathology investigations wereconducted on these fish, and found no likely cause of death. Based on these findings, thefish were most likely caught by fishers and subsequently discarded as bycatch. Seewww.qld.gov.au/gladstoneharbour for more details.Observational findings Phase 2April 2012 sampling: The following numbers of the candidate fish were observed at thethree sites during the April sampling event. Bundaberg: no grinner; 105 herring; 105 Australian threadfin Gladstone Harbour: 20 grinner; 20 herring; 100 Australian threadfin. Fitzroy River: 16 grinner; 15 herring; 100 Australian threadfin.No significant signs of ill health were observed in trawl fish species caught during the trawlsampling from offshore Bundaberg, the Gladstone Harbour or from offshore of the FitzroyRiver.June/July sampling: The following numbers of the candidate fish were observed at thethree sites during the June/July sampling event: Bundaberg: 18 grinner; 10 herring; 25 Australian threadfin. Gladstone Harbour: 26 grinner; 100 herring; 100 Australian threadfin Fitzroy River: 100 grinner; 100 herring; 100 Australian threadfin.Two Australian threadfin caught at Bundaberg and a single Australian threadfin caught inGladstone Harbour had isopod parasites present either on the gills or body surface. Otherthan the presence of the isopod parasites, no signs of ill health were observed in the fishspecies collected during the trawl survey at the three sites.Laboratory findings Phase 2The grinner, Australian threadfin and herring specimens were preserved fresh on-board atrawl vessel by a veterinarian with aquatic animal expertise. Other than gross observationsmentioned above and length records, no necropsy data was collected for these species. Asub-sample of grinner was chosen for histopathology and chemical residue testing, and allother samples were archived for further testing if required.HistopathologySkin, liver and gill samples from each of the 25 fish were assessed histologically and rated inthe same way as has been described previously for barramundi. There were no significant ornotable differences between Gladstone Harbour and the reference sites for any tissues – thefish appeared normal. These fish tissues were preserved immediately following euthanasia toeliminate any deterioration of tissues and allow detection of very subtle abnormalities. Therewas no evidence of any unusual gill or skin irritation occurring in the fish from GladstoneHarbour.Chemical residue testingAluminium, iron, copper and zinc were significantly higher (P < 0.05) in grinner musclecollected at Bundaberg (reference site) compared to other sites, but there were no otherdifferences in metal concentrations between sites. Differences in metal concentrations66