Two dolphins found washed up on Northern Territory beaches have raised questions about the future of life in Darwin Harbour and semantics about the word 'dredging'.
Australian humpback dolphins, snubfins and bottlenose dolphins are found off the NT coast, but harbour users fear numbers have decreased in recent years.
Two dolphins were found dead on Casuarina and Lee Point beaches last month.
Charles Darwin University dolphin researcher Carol Palmer has been following local dolphins for about 15 years.
Dr Palmer found a third dead dolphin almost a year ago in the same place.
Nobody knows what killed them.
Boom town too noisy
Darwin has become a much busier place in the past 20 years as large gas plants have attracted bigger, deeper ships, resulting in seabed clearing.
Darwin's population has also grown, and there are more recreational fishing boats, jet skis, air boats, tour boats and sailing boats than ever.
"We realised in 2012 there appeared to be a decline in dolphins," Dr Palmer said.
"With all the activity in the harbour, it's distracting for them.
"As things get noisier in the harbour, do they just not return to Darwin Harbour?
"They're notionally low in numbers, and once you start to lose a few adults you start to lose populations."
Dredging allows bigger gas ships, and more dredging is expected with further projects.
"With dredging, I think we need to change the words to 'sea clearing'," Dr Palmer said.
Jobs or wildlife?
Sea Darwin tour boat operator Jim Smith said in 2008 he could promise a 50 per cent chance of dolphins.
"I don't know when was the last time we saw them," he said.
"You're lucky to see them in the harbour."
Mr Smith is on the Darwin Harbour Advisory Committee.
"There's an incredible amount of industry lining up to use the harbour for various reasons," he said.
"One way for our community to help is to have a Darwin Harbour dredging committee but it could be seen as an obstacle to jobs.
"We know enough about human activity and the impact it has on the environment.
Sightings needed
Environment Centre NT energy campaigner Jason Fowler has called for anecdotal dolphin sightings.
"You'd expect in the future you'd be very lucky to find any sort of marine megafauna — which is dolphins, turtles, and dugongs — in the harbour at all," he said.
He has pointed a finger at the NT government and "the two gas plants".
No smoking gun
The NT Environment Department examined the dead Lee Point dolphin and ruled out "obvious external trauma or abnormal organ or tissue damage", but ruled in a stingray barb as a possible culprit.
The second dolphin, a humpback calf, was too decomposed to determine the cause of death.
"A major monitoring program of dolphin populations in Darwin Harbour from 2011 to 2019 highlighted the small, mobile and variable nature of dolphin populations in the Darwin region," a spokeswoman said.
"There is significant variation between years and movements between parts of the harbour, which may contribute to some people's perception of large changes over time."
She said reported dead dolphins were usually ill.
"Where possible, all strandings are assessed by the NT government's Berrimah Veterinary Lab and reports on stranding of marine megafauna in the NT are available on the web," she said.
No pollution had been reported recently to the NT EPA, and the spokeswoman cited the annual Darwin Harbour Report Card results since 2009.
"This consistently shows water quality in almost all parts of the harbour to be good or very good," she said.
'Duty of care'
Santos, which operates Darwin LNG at Wickham Point, was contacted for comment.
Inpex operates the Ichthys LNG onshore processing facility.
"At Inpex, we are committed to protecting the environment in which we work," a spokeswoman said.
"We acknowledge our duty of care to both the natural environment and the communities in which we operate, and support and maintain a culture where people are empowered to intervene to prevent environmental harm.
"We work together with NT government, local industry, ranger groups, and the broader community to protect the biodiversity and health of this important ecosystem.
"Our operational activities are managed to comply with an NT EPA-issued Environment Protection Licence, with third-party statutory audits and independent reviews to verify monitoring data and reporting."
