Court ruling in Invercargill
Ryan Campbell McManaway, 36, was sentenced in his absence at the Invercargill District Court on 26 September 2025. He faced four charges under the Fisheries Act after a Ministry for Primary Industries (MPI) investigation uncovered an illegal seaweed harvesting and sales operation.
The court fined McManaway $50,000 for the fisheries offences, along with a further $3,000 for failing to comply with directives to attend an interview with fishery officers.
How the case unfolded
The investigation began in November 2022 when MPI officers discovered an online advertisement offering liquid seaweed fertiliser. The product was being sold in 1,000-litre containers for $500 or in 20-litre buckets for $20.
A search warrant executed at McManaway’s property revealed 14 large containers of fertiliser made from Macrocystis pyrifera, also known as giant kelp. This species is valued for both fertiliser and food uses. Officers also found an industrial mincer with seaweed traces and other processing equipment.
No rights to harvest
Fisheries New Zealand’s southern regional manager, Garreth Jay, said McManaway was no longer a licensed commercial fisher at the time of the offences.
“Mr McManaway had no legitimate right to harvest and sell this seaweed as a fertiliser,” Jay said. “He could’ve potentially earned several thousand dollars from this operation. When we find evidence of people breaking the rules that protect our fisheries resources and the livelihoods of legitimate commercial operators, we will hold them to account.”
Why seaweed matters
Seaweed is a cornerstone of marine ecosystems. It provides food and shelter for countless coastal species, from small invertebrates to fish. Because of its ecological role, New Zealand strictly regulates commercial seaweed harvest with a permitting and reporting system.
Illegal harvesting not only undermines sustainability but also disadvantages licensed operators who follow the rules. MPI says it will continue to target and prosecute those who profit at the expense of the environment and legitimate businesses.
