Department of Conservation concern about the health of seagrass in the Kaipara Harbour is frustrating plans for the country's biggest oyster farm.
Baby snapper and goatfish use patches of seagrass on sandbanks to hide from predators.
Warkworth-based Biomarine wants to occupy 104ha of the remote harbour, saying that elite oysters
fattened in the clean waters will earn $18 million annually in exports and create 150 jobs.
Its four-year struggle with red tape to set up the farm has moved Rodney Mayor John Law to commend the venture to Auckland Regional Council commissioners who are hearing the company's case for coastal permits.
Mr Law says Biomarine is a respected pioneer of the aquaculture industry and a "business citizen" who has contributed to improving water quality in the Mahurangi Harbour on Rodney's east coast.
Biomarine director Jim Dollimore said he had expected a decision from commissioners by last Tuesday but DoC evidence about seagrass had now caused the hearing to be put off until next month.
Assertions in the evidence were based on an uncompleted ARC report on its study of the South Kaipara seabed. This had not been seen by Biomarine and the 33 objectors to its plans.
More time was needed for the report to be finished and all parties given time to respond.
Glen Houghton, counsel for the Director-General of Conservation, said seagrass lay under one-third of the proposed farm and was such an important part of the site's ecology that the department wanted it left out of the plan.
Protection of seagrass was a matter of national importance, she said.
Juvenile fish and wading birds would lose their homes if oyster farm structures shaded the seagrass from its life-giving light.
Biomarine says its check of Parengarenga Harbour in the Far North showed large areas of seagrass under oyster farms that had been there for 30 years.
Marine ecologist Mark Morrison said seagrass growth was dynamic at the proposed Kaipara farm site.
Seagrass had also increased at Snells Beach, where a large beach had changed from bare sand to an extensive seagrass bed, and was re-establishing itself at St Heliers Bay.
Mr Dollimore said the consent conditions would demand strict monitoring of seagrass to check for depletion.
