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

Encysted larval parasites were found internally, but were not expected to be causingsignificant effects on the health of the sharks.There was minimal or no detectable sediment in the gills of the shark samples.Observational findings Phase 2April: Bull sharks were collected from all proposed sites except for Rodds Bay. Sampling ofbull sharks proved difficult during the April period with a total of 23 caught. Anecdotalevidence from commercial fishers suggests that bull sharks start leaving the estuaries at thistime of year. Three sharks of other species were also caught (two blacktip whaler, one Creekwhaler) and their condition recorded.Conditions observed with sharks caught during the April sampling period consisted of skinredness and areas of detached scales predominantly between the first and seconc dorsalfins exposing the skin, as well as some scratch marks around the affected areas. No othersigns of ill health were observed at the time of capture. A summary of results is shown inFigure 37.Conditions observed in Bull Sharks sampled at each site during April, Phase 212Skin Colour Normal Skin Minor Redness Areas of detached scales (indicative of ectoparasites)10Number of sharks86420Fitzroy River(n = 7)Hamilton Point(n = 1)Calliope River(n = 3)lower Boyne River(n = 10)upper Boyne River(n = 1)Bundaberg(n = 1)LocationFigure 37 Conditions observed in bull sharks at the time of capture from all sites sampled during April2012. Note, (n) refers to the total number of sharks examined at each site. Some sharks may have beenobserved with multiple conditions.Skin redness was observed on sharks caught from most areas, including those caught at thereference sites. The redness observed at the time of capture was classified as minor rednessand was most obvious on the lighter ventral surface of the sharks. The extent of redness wasdifficult to quantify consistently, given redness increased significantly post mortem asillustrated in Figure 38. The two sharks pictured were captured in the Calliope River and bothwere classified as having no redness in the field immediately after capture. After beingindividually bagged and kept on ice for approximately four hours, both sharks displayedsignificant redness.58