Ngāi Tahu Seafood Resources Ltd has applied to build a large-scale salmon farming operation in Foveaux Strait, about 2km off the coast of Stewart Island. New technology involving electromagnetic barrier deterrents may also be used to deter sharks from the farm.
The Hananui Aquaculture Project, which is being processed under fast-track legislation, is estimated to contribute about $500 million in annual gross revenue, representing a 150% to 200% increase over current national salmon farming export revenues.
The process is at the stage where identified stake-holders have been invited to comment.
The majority of the 17 submissions have been supportive.
The applicant said there were no adverse effects sufficiently significant to be out of proportion to the project’s regional and national benefits.
Department of Conservation senior technical adviser Jody Weir said Stewart Island was now a breeding colony for sea lions, with 95 pups born in the latest season.
She said changing dynamics between existing salmon farms in Big Glory Bay and sea lions were already demonstrating some of the ways the presence of captive salmon/prey could change the natural behaviour of sea lions.
Her primary concern was energy-rich salmon would attract both sea lions and fur seals to the area.
‘‘If there is even a single release of live salmon into the environment or any opportunity ... to taste/access a salmon within the pen ... they will quickly learn and habituate to this new easy food source,’’ she said in a report.
‘‘It could also lead to the animals becoming more desensitised to humans, making them more bold and potentially aggressive in their efforts to access this newfound ... food source.’’
She was not convinced predation could be stopped by the use of the predator-resistant material.
‘‘Studies overseas have demonstrated that if not effective in completely keeping pinnipeds from accessing the fish, the animals will learn how to access the fish very quickly and the behaviour will be impossible to reverse.’’
Pinnipeds are a group of species that include seals, sea lions and walrus.
Finfish farms were known to attract large marine predators, including sharks, and in some cases sharks could become resident around finfish farms, the application said.
Earth Sciences NZ fisheries scientist Brittany Finucci said it was inevitable white and sevengill sharks would be attracted to the proposed farm.
The applicant was looking to use predator-resistant materials in the construction of nets. It would have a mesh size which minimised a predator’s ability to penetrate the net with their head, fins or tail.
It was also considering new technology such as electromagnetic barrier deterrents to try to combat sharks from coming near the fish farms.
Doc senior marine science adviser Karen Middlemiss said the applicant had sufficiently outlined in the shark management plan the mitigations/actions required to protect sharks from potential interactions with the fish farm.
Seafood New Zealand was allowed to submit a late comment. It generally supported the proposal but raised concerns about its impact on the greater ocean.
‘‘We do remain concerned with the cumulative effects of spatial closures in the Otago/Southland area’’
