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

Figure 38. Sharks caught in the Calliope River illustrating the increase in skin redness post mortem. (a)and (c) Shark #0005 and #0007 photographed in the Calliope River at the time of capture; (b) and (d) Thesame sharks photographed four hours later in the lab.Areas of skin between the first and second dorsal fin with placoid scales absent were alsoobserved on sharks from most areas, including reference sites (Figure 39). This symptomhas been previously associated with the presence of the monogenean parasiteDermophthirius maccallumi during Phase 1 sampling. Therefore, it was considered to beevidence that monogenean ecto-parasites were present even when the parasites themselveswere not seen. This assumption was also based on personal communications with Dr IanWhittington, who suggested that only adult monogeneans from the family Microbothriidaewould be visible on the skin in the field, as juvenile worms are generally located underneaththe scales and would be too small and hidden from sight for visual identification.Figure 39. Bull sharks caught at Bundaberg and the Calliope River showing evidence of ecto-parasites(lighter areas) between the dorsal fins.June/July: No bull sharks were collected during the June/July sampling event. Commercialfishers suggested that bull sharks leave the study area during the winter months.When considering the findings from the sampling program (Phase 1 and Phase 2) the mostcommon abnormalities observed in sharks and rays was skin redness, and lesions locatedbetween the dorsal fins. Pathology investigating skin redness during Phase 1 found noassociated pathogenic organisms, so the cause of this condition is unknown. Given sharks,59