This study summarizes 660 events involving captured, live-stranded and dead cetaceans in
South Australia between 1881 and 2000. Emphasis is placed on records (n = 361) during
1985-2000 when an active necropsy programme was underway. Average number of events per
year was 30.4 and the most common species were the short-beaked common dolphin
(Delphinus delphis) and Indo-Pacific bottlenose dolphin (Tursiops aduncus). Records were
assigned to nine categories of circumstance/cause of death. Summarizing the total database,
60% were unknown circumstance, 22% not obviously anthropogenic, 13% unintentional
human-related and 5% intentional human-related. In the data set of records for 1985-2000,
50% were unknown, 25% were not obviously anthropogenic, 20% were unintentional humanrelated
and 5% were intentional killings. Non-anthropogenic circumstances included neonatal
deaths, live strandings, significant diseases, shark attacks and choking. Cornynebacterium
ulcerans is recorded for the first time in a cetacean. Unintentional circumstances included
entanglement in fishing and aquaculture equipment (17% of necropsied carcasses from
1985-2000) and boat strikes. Intentional human-related circumstances were captures for live
display and illegal killing. Five percent of the necropsied carcasses during 1985-2000 were
attributed to shootings or stabbings/spearings. There is need for a formal reporting procedure
for marine mammal deaths and human interaction involving injury and for steps to be taken to
reduce human impacts.
Cases of morbillivirus have been recorded in the Southern Hemisphere but have not been linked to significant marine mammal mortality. Post-mortems were conducted on 58 carcasses (44 Indo-Pacific bottlenose dolphins, two common bottlenose dolphins, 12 short-beaked common dolphins) from South Australia during 2005–2013, including an unusual mortality event (UME) in St Vincent Gulf Bioregion (SVG) during 2013. Diagnostic pathology, circumstance of death, body condition, age and stomach contents were documented for Indo-Pacific bottlenose dolphins. At least 50 dolphins died during the UME, 41 were Indo-Pacific bottlenose dolphins and most were young. The UME lasted about seven months and had two peaks, the first being the largest. Effect on the population is unknown. Diagnostic testing for morbillivirus was conducted on 57 carcasses, with evidence for infection in all species during 2011–2013. All tested UME bottlenose dolphins were positive for cetacean morbillivirus (CeMV), and the pathology included interstitial pneumonia, lymphoid depletion and syncytia. Concurrent pathologies, including lung parasite and fungal infections, and severe cutaneous bruising were observed in many dolphins. The event coincided with elevated water temperatures, a diatom bloom and significant fish die-offs. We conclude that the cause for the UME was multifactorial and that CeMV was a major contributor.
Cetacean carcasses near Port Lincoln and entanglements in southern blue-fin tuna feedlots were monitored between 1990 and 1999. Dolphins became entangled and died in large-mesh (usually > 15cm) anti-predator nets around the cages, from surface to seafloor (18m). The carcasses were retrieved and studied with respect to diet and life history. During the period of study, 29 dolphins (15 bottlenose, 9 common, 5 unidentified) were confirmed entanglement deaths and an additional eight unconfirmed reports of dead dolphins were made between 1993 and 1996. Beach-washed or floating carcasses of an additional 38 dolphins were found in the Port Lincoln region during 1990-1999, four of which were suspected entanglements. The carcasses of 23 entangled and four suspected entangled dolphins were studied for diet, and reproductive and relative age characteristics. At least 24 of the 33 entangled animals were juveniles or sexually mature animals, of which most of the females were pregnant or lactating. Three calves and no neonates were entangled. Gastrointestinal contents of 57 bottlenose and common dolphins from elsewhere along the coast of South Australia were also studied. Cephalopods were more abundant in bottlenose dolphins than common dolphins, including those entangled in tuna feedlots. Carangidae were the main identified fish prey of dolphins entangled in tuna nets. The study concluded that dolphins were being attracted to, and feeding in, the area of the cages. Recommendations for minimising entanglements include removing anti-predator nets or reducing mesh size to less than 8cm, reducing tuna food wastes and thereby the food source for other fish in the vicinity, and rigorous monitoring of both entanglements and dolphin populations in the Port Lincoln region.
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