Going, Going…Dugong

dugong

The crane hoisted the slippery, nearly 500 kilogram dugong onboard the ‘Sea World One’ research vessel. Once the animal is placed safely on a mattress, the team launches into a highly coordinated routine taking blood and urine samples and measuring levels of reproductive hormones. If the dugong is a male they will take semen samples and if it is a female they will check for pregnancy with an ultrasound.

The team, consisting of people from Sea Life Aquarium, Sea World and the University of Queensland, were investigating the health of dugongs surrounding Moreton Bay in late July. The Great Barrier Reef is home to one of the world’s largest dugong populations, though their numbers have steadily declined over the years. Now, the controversial approval of the Abbot Point port expansion has reinvigorated concerns for the species.

“If they [the Government] had any common sense they wouldn’t do what they’re doing,” said Ms Shona Lorigan, a representative from the Organisation for the Rescue and Research of Cetaceans in Australia (ORRCA), which monitors the dugong population and advises on marine animal management. “The dredging is going to have a profound impact.

“The [dugong’s] population dynamics make them very susceptible to changes in the environment …they don’t have a robust population.”

Originally the five million tonnes of seabed that will be dredged to expand the port was going to be relocated in the Great Barrier Reef. However, pressure from environmental groups has forced developers to submit a new proposal to Environment Minister Greg Hunt which includes an onshore location for the sediment. Despite this new proposal, environmentalist groups including ORRCA and the Australian Marine Conservation Society (AMCS) remain adamant that the expansion will destablise the environment dugongs depend on.

Ms Lorigan said the primary concerns would be the effect of the turbidity from dredging on the dugong’s primary food source, seagrasses, and the increase in the number of boats in the area.

“A lot of turbidity…that can effect seagrass and massive amounts can die off …that’s going to be the big threat to them,” she said, “there’s [also] going to be an increased chance of boat strike.”

The World Wildlife Fund (WWF) states that the Great Barrier Reef’s dugong population is “globally significant” and contributes to the area’s World Heritage status. Approximately 85,000 dugongs live in Australia’s northern waters between Shark Bay in Western Australia and Moreton Bay in Queensland. According to the WWF, this is three-quarters of the global population. Populations around the world are otherwise fragmented. In parts of Cambodia, Laos and the Maldives dugongs may already be extinct.

There are an estimated 12 to 15 thousand dugongs in the Great Barrier Reef. However, only about 600 dugongs were in the World Heritage Area south of Cooktown in 2011, down from a population of 2000 in 2005.

Dugongs are the only marine herbivorous mammal. Most of their time is spent grazing on seagrass which grows inshore, leading to their nickname as ‘sea cows’. They are often spotted when they come to the surface to breathe.

They can live up to 70 years old, but reproduce only rarely. Research conducted by Dr Helene Marsh found that males and females are not sexually mature until at least 10 years old, while some females will become sexually mature as late as 17 years old. After a 14 month pregnancy, a female will give birth to a single calf which will stay by her side for about 18 months. A dugong may have one calf anywhere between every two and a half and five years.

This slow reproduction rate means the dugong population can decline rapidly. The Great Barrier Reef Marine Park Authority’s (GBRMPA’s) Strategic Assessment Report for 2014 stated that “the maximum population growth rate…[is] up to six per cent annually,” if dugong’s had an exceptionally low mortality rate.

“The population can’t handle any increase in mortality rates,” Ms Lorigan said. “One single mortality event can have a huge effect.”

But the dugong’s mortality rate has historically been high. Thousands were harvested between 1847 and the 1930s and many died from being caught in fishing nets during the 1960s. According to the GBRMPA’s Strategic Assessment Report, by the 1990s dugong numbers had declined by more than 90 per cent. It states “a decline of 8.7 per cent per year between 1962 and 1999” was indicated by the numbers of dugongs caught in nets at 47 separate beaches.

Since, Dugong Protection Areas and changes to net designs have aimed to reduce dugong mortality.

The World Conservation Union (ICUN) and Convention on International Trade in Endangered Species (CITES) have both recognized the risk of the species becoming extinct.

Dugongs are listed under the Environment Protection and Biodiversity Conservation Act 1999 and as vulnerable under the Nature Conservation Act 1992. They are also protected by the Great Barrier Reef Marine Park Regulations 1983. There is an exemption allowing indigenous people to hunt dugongs under the Aboriginal Land Rights Act and Native Title Act.

The GBRMPA’s Outlook Report for 2014 stated that dugongs are still recovering from the impacts of cyclone Yasi in 2010 on seagrass meadows. Seagrass meadows have also declined in abundance due to the impacts of catchment run-off and dredging projects. This has increased the number of dugong deaths and forced them to move from the Great Barrier Reef.

After the approval of the Abbot Point port expansion, the United Nations Educational, Scientific and Cultural Organization (UNESCO) issued a warning that it would list the Great Barrier Reef as ‘in danger’ if the Australian government did not show how environmental problems, including the protection of vulnerable species, were being addressed within a year.

Mr Jim Devine, a representative from the Queensland Resources Council, stated that the dumping of the dredged sediment offshore could be done in a way that it wouldn’t impact on the environment.

“People forget how big the Great Barrier Reef is….the reef is 2300km long. It’s as big as Italy!” he said. “The sediment would be moved somewhere that’s quite barren… Seagrasses have been carefully mapped so they aren’t damaged…projects also work around dugong breeding seasons.”

The Australian Marine Conservation Society’s Chief Campaigner Ms Felicity Wishart denounced the offshore dumping plan as an unnecessary risk. She said disposing the sediment onshore was a better option because the sediment could smother corals and seagrasses and decrease water quality.

A study run by the Australian Research Council’s Coral Reef Studies Centre of Excellence recently found that dredging decreases the health of coral reefs. The study was conducted near Barrow Island, off the West Australian coast, close to where an 18-month, 7 million cubic metre dredging project took place.

Mr Devine claimed that there was no evidence that dredging had a significant impact of seagrasses if located about 40 kilometres away from marine habitats, as in the case of the Abbot Point port expansion.

“We can control these projects,” he said. “At this level it is manageable…it will not have regional effects.”

But the study provided the evidence environmentalist groups needed to delay the dredging. To avoid financial losses, North Queensland Bulk Ports, GVK Hancock and Adani Group are investigating onshore disposal options.

This has satisfied people within the tourism industry who opposed the dredging due to the effect the sediment would have on water visibility. It has not, however, satisfied environmental groups.

Ms Lorigan stated that currently there is not enough being done to protect dugongs and that they will be more at risk when the dredging takes place.

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