Commercial fishermen began outlining their case in the High Court at Wellington on Monday to overturn bans and restrictions on set netting, trawling and drift netting in coastal waters.
The regulations were imposed by then fisheries minister Jim Anderton last year to protect rare Hectors and Mauis dolphins.
The Federation of Commercial Fishermen says the Mr Anderton acted on poor advice.
The federation's lawyer, Bruce Scott, told the court the regulations will affect the livelihood of many commercial fishermen.
Mr Scott says the rules will cost the industry $79 million over the next five to 10 years.