The Environmental Protection Authority was told in Blenheim on Tuesday the long term economic benefit of developing more salmon farms in the Marlborough Sounds would be about $880 million on the next 25 years.
New Zealand King Salmon already has five farms operating and is applying to build nine more farms.
The application has attracted 1400 submissions - 800 against and 400 in support.
Environmental groups claim the seafloor and water quality will be destroyed due to excessive waste from feeding fish.
Lawyer James Gardener-Hopkins said that is not true, and it is a long standing principle of planning and resource management law that opposition to a proposed use - even by a large number of people - is not itself a relevant consideration.