Fisheries Minister Rory McEwen said the closed season for taking cod from the river would be extended by one month and bag and size limits would also be changed.

Under the new regulations Murray cod may not be taken between August 1 and December 31 each year.

The daily bag limit for each fisher will be reduced from two to one, while the boat limit will be cut from six to three.

The minimum size for legal cod will be increased from 50 centimetres to 60 cm.

Mr McEwen said recent research pointed to a lack of cod in the South Australian section of the Murray, as a result of low water flows and reduced turbidity because of the drought.

"It's important that the current size of the Murray cod population is maintained to ensure that spawning success and recruitment to the fishery can occur when there are improved river flows and enhanced habitat conditions," the minister said.