International oilfield services company Schlumberger and energy data provider TGS have proposed conducting seismic blasting with high-powered airguns over a 7.7-million-hectare area in Bass Strait.
To find gas offshore, gas companies engage in seismic surveys, releasing compressed air to send sound waves to the ocean bed to test for oil and gas reserves.
If approved, this would be one of the largest seismic exploration projects undertaken, covering an area larger than Tasmania, however, one environmental group has expressed concerns about the possible ecological and financial impacts.
Friends of the Earth campaigner Freja Leonard says as part of the testing, seismic blasts of up to 250 decibels will go off every 10 seconds for months at a time.
Ms Leonard says gas is a damaging product at every stage of its exploration process.
"It happens offshore so people don't see it, they don't hear it and it's completely out of mind," she said.
"We feel like it's important for people to understand the incredibly damaging consequences of gas, right from the point of exploration."
If the proposal is approved, it could still take years before the exploration could go ahead.
"One of the other concerns is, by the time that gas is produced and ready for market, there's every chance that it's an entirely uneconomic prospect," Ms Leonard said.
She said the surveys could have a damaging effect on marine life, killing smaller species such as zooplankton and krill as well as deafening aquatic mammals.
"Whales and dolphins rely on sonar for communication and navigation to find food so a deaf whale and dolphin is a dead whale and dolphin," Ms Leonard said.
Australian Petroleum Production & Exploration Association chief executive Samantha McCulloch says fisheries and the oil and gas industry do successfully co-exist.
"The oil and gas industry works in a comprehensive regulatory environment that considers all relevant science and potential risks to the environment," she said.
"Members are also required to ensure activities consider and manage any impacts on other marine industries."
Concerns for fishing industry
Ms Leonard said the seismic works were also likely to affect the fishing and ecotourism businesses.
"We've never seen a project this size before, so we can't anticipate what the potential consequences are," she said.
"We can expect they will be broad, far-reaching and incredibly damaging."
Southern Rock Lobster Limited executive officer Tom Cosentino said the industry had conducted a number of trials into the effect of seismic testing on lobsters, but noted the trials did not perfectly replicate an operational work environment.
Mr Cosentino said the testing did not kill lobsters, however, it could have other impacts.
"It can impair the lobsters' inner ear, so it can have an impact on their ability to flick themselves back upright, which assists them [in] getting away from predators," he said.
"Exposure to air-gun testing can lower red blood cell numbers and lead to lower immune responses.
"There was a decrease in their nutritional makeup, as well. So, [we're not sure] whether they're either not digesting as well as they can or they're not in a position where they can go out and hunt food."
Mr Cosentino said the industry was not worried given the testing did not have an immediate impact on lobster numbers.
However, he says it is important to work with the gas companies while the surveys are being conducted.
"We ask that they do them in off-seasons, we also ask that they do the testing as far away from our fishing blocks as possible," Mr Cosentino said.
"We do have to share ports at times but we're not going to be treading on each other's toes."
Schlumberger and TGS have been contacted for comment.
