Conservationists and anglers have started scrutinising Japanese giant Inpex's draft environmental impact statement for its planned $12 billion Darwin Harbour gas plant.

Inpex (TYO:1605), which has been a member of the Australian business community since 1986, says it would need to blast away rocks to make a new shipping channel for its gas plant.

Chris Makepeace, who represents the Amateur Fishermen's Association, says there are numerous environmental concerns to address, but the possibility for fish to be killed by blasting is not the main issue.

"I don't think it will be too many days before there aren't too many fish in close proximity to where the blasts are going on," he said.

"Fish aren't that stupid."

He is pleased Inpex has reduced the length of the proposed shipping jetty from 3.5 kilometres to 500 metres so that access to the Catalina creeks will not be blocked.

Mr Makepeace says the decision is not an indication of the fishing lobby's power.

"I'd love to be able to say that a huge Japanese-French conglomerate has designed a $12 billion gas plant around what AFANT has told them, but I really don't think that's what's happened.

"I think there have been a whole lot of considerations here.

"I mean I'm sure they have taken into account what we talked about with them."

Northern Territory Environment Centre's Stuart Blanch says the blasting will drive away dolphins.

"Blasting [the] Walker Shoal probably means the disappearance of humpback dolphins from that part of the harbour maybe for many, many years," Mr Blanch said.

"I understand that they can use a different route by moving a submerged barge," he said.

"I want to hear Inpex come out with a plan B to blasting Walker Shoal."

In response, Inpex says it will monitor the harbour to make sure no endangered species are killed if its project goes ahead.