The Supreme Court is hearing two legal challenges to plans by King Salmon to expand its salmon farms in the Marlborough Sounds.
King Salmon originally wanted to put nine salmon farms in a protected part of the Sounds but a board of Inquiry rejected five of the sites.
The Environmental Defence Society challenged that decision in the High Court, but its appeal was dismissed.
Now the Society and the group Save Our Sounds are taking appeals to the Supreme Court on Tuesday.
Questions for the Court to decide include matters relating to the New Zealand coastal policy statement and also the environmental effects of the plan change needed for the salmon farms to go ahead.