Watch NZH Local Focus: Environmentalists give evidence opposing seabed mining

Scientists have just conducted their annual survey of blue whales in the South Taranaki Bight, where Trans Tasman Resources wants to start seabed mining.

This year they documented 68, more than double last year's total of 33.

Dr Leigh Torres gave evidence at the Environmental Protection Authority's hearing into the mining proposal. She was counting the mammals and said seismic surveying is already having an impact.

"Blue whales change their behaviour and get stressed out when there is seismic surveying going on. It's an incredibly loud noise, and so if you add onto that some other low-level background noise, I believe you might push them towards a tipping point. We already are seeing consequences. We see whales out there that look skinny to us, you can see their backbone," says Dr Torres.

Trans Tasman Resources wants the right to extract up to 5 million tonnes of iron sand a year from a 65 square kilometre area of seabed off South Taranaki coast.

It's applied for a license that would last up to 35 years.

Otago University Zoology Professor Dr Elisabeth Slooten says if Trans Tasman Resources gets the go ahead, the operation will have a significant impact on marine mammals like the critically endangered Maui Dolphin.

"The potential impacts include direct impacts such as ship strike, injury, and disturbance caused by noise. They also indirect impacts such as ecological changes caused by the mining," says Dr Slooten.

While research is conducted into marine activity, Dr Slooten says the data is not comprehensive.

"There's no way we can estimate the number of individuals of each species that will be affected by noise, through physical injury, or behavioural disturbance, or that may be impacted by other effects from the mining operation," says Dr Slooten.

The hearings are scheduled to continue for another 3 and a half weeks. No date has been set for a decision.

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