Survival of spores of the oyster pathogenMarteilia sydneyi (Protozoa, Paramyxea) as assessed using fluorogenic dyes 'Department of Parasitology. The University of Queensland. Brisbane 4072, Australia 'Protozoa Section. Queensland Museum. PO Box 3300, South Brisbane 04101, Australia ABSTRACT: Sporonts of the paramyxean protist Marteilia sydneyi, aetiological agent of 'QX' disease in the Sydney rock oyster Saccostrea commercialis, were isolated from infected oysters and maintained under various physical conditions to assess their survival. Survival was determined using 2 fluorogenic dyes, propidium iodide and 4', 6-diamidino-2-phenylindole. The effects of salinity, temperature, ingestion by natural oyster predators, freezing and chlorination were examined. Dye exclusion indicated that spores were short-lived once isolated from the oyster, with the majority dead within 7 to 9 d. Maximum longevity recorded was 35 d at 15'C and 34 ppt. Experiments to investigate the effects of ingestion by fish and birds revealed that spores did not survive for more than 2 h under these conditions, suggesting that it is unlikely that fish or birds play a significant role in the life cycle or dispersal of this parasite. Spores apparently remained viable for over 7 mo when frozen at -20 and -70°C. Chlorine treatments of 200 ppm killed 99.5% of spores within 2 h and all spores within 4 h of exposure.

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Two outbreaks of Marteilia sydneyi in oysters near the mouth of the Brisbane River are described. Before the first outbreak the pH fell slightly, but before the second outbreak it remained unchanged. Changes in salinity and temperature were minor. The results indicate that these epizootics of M. sydneyi were not correlated with fluctuations in pH, salinity and temperature of water in close proximity to the oysters.

Recreational fishing gear continues to evolve, and factors such as anatomical hooking location may change over time due to technology creep. We revisited studies conducted in 1996 by re-examining hooking location in experiments where hard-bodied and soft plastic lures were presented to stripey (Lutjanus carponotatus) and wire netting cod (Epinephelus quoyanus) either with or without application of a synthetic fish attractant. These data were compared to those of fish hooked on organic bait using circle or J-style hooks. Lure type and application of attractant both significantly affected hooking location. Addition of attractant to hard-bodied lures reduced foul hooking of both species. For L. carponotatus, soft plastic lures both with and without attractant tended to be taken deeper than hard-bodied lures. For E. quoyanus captured on soft plastic lures coated with attractant, hooking locations were similar to those using organic baits on circle hooks. However, deepest hooking of both species occurred using organic bait on J-style hooks. The use of soft plastic lures with an effective fish attractant may result in deeper hooking, which could potentially influence post-release survival and increase fishing power.

Coral reefs worldwide are under increasing stress from anthropogenic impacts, but there are relatively few reports of increased rates of disease in coral reef fish. Herein we report the emergence of abnormal skin lesions in wild-caught wire netting cod (Epinephelus quoyanus) near Heron Island in the southern Great Barrier Reef. The lesion involves conspicuous darkening and disorganisation of the brown ‘wire netting’ colouration pattern typical of this species, most commonly on the lower jaw, premaxilla and head, with occasional involvement of the flanks and dorsal fin in some fish. The lesion was not present during research conducted in the mid-1990s; however, since it was first recorded in 2012, the prevalence of grossly visible lesions has increased to 16.9% in 2017, with fish >340mm long most affected (prevalence 64.7%). These data suggest emergence of the lesion is a recent phenomenon and that causative factors may be age related. Abnormal pigmentation lesions have only been observed to affect E. quoyanus and coral trout (Plectropomus leopardus; since 2010). Given the species affected and the currently unknown aetiology of these lesions, we name the condition serranid pigment abnormality syndrome (SPAS). Further research is required to determine its geographic distribution, establish causation and describe the course of disease in E. quoyanus.