Catch limits for Blue Cod have changed in the South Island in a bid to rebuild population numbers

The commercial catch limit for Orange roughy will increase by 18 per cent -- as will snapper in the Tasman region.

But, the catch of Blue cod in Southland will be reduced by more than 500 tonnes.

Seafood New Zealand Chief Executive Jeremy Helson says they're happy to reduce numbers in the name of sustainability.

He says the science indicated that blue cod might need a reduction -- which is the beauty of the quota management system, because it responds to increases and decreases in fish numbers.