The Government has banned fishing for blue cod in the Marlborough Sounds saying stock in the region is in "serious trouble".

The ban covers all enclosed waters in the Marlborough Sounds including Pelorus, Kenepuru, Queen Charlotte Sounds and Tory Channel.

Fisheries Minister Jim Anderton said the ban would be enforced from October 1 this year and would expire on October 1 2012.

"People remember the large numbers of blue cod that could be caught in years gone by, but that is no longer the case.

"The Marlborough Sounds blue cod fishery is in serious decline," Mr Anderton said.

He said measures already in place to try and address the decline - most recently reducing the daily catch limit to three blue cod per person and increasing the minimum size - had failed.

"Unfortunately, none of these measures have worked and the decline in blue cod numbers has continued. This leaves me in the position of having to take strong action or risk not having a blue cod fishery in the Marlborough Sounds at all."

Mr Anderton said there had been an average reduction across Marlborough of 57 per cent of juvenile blue cod from 2004, with the inner Queen Charlotte Sound reporting no blue cod at all.

He said pressure on stocks was expected to increase with the rising popularity of recreational fishing, new technology and building evelopment in Marlborough.

Mr Anderton said the Fisheries Ministry had received over a thousand submissions on protecting the blue cod fishery.

"There has not been universal agreement over what measures to take, although the majority of submissions supported further action to protect the future of this fishery, with most supporting closed areas," he said.