The fishing industry is fighting Government restrictions aimed at protecting Hector's dolphins and Maui's dolphins.
Regional restrictions on set netting, drift netting and trawling are due to come into force from October.
The Federation of Commercial Fishermen is challenging the measures in the High Court in Wellington, arguing jobs and businesses are at risk.
The federation says it does not want to harm the dolphins and is asking only for seasonal relief where jobs are under immediate threat.
It says the changes will drive people out of business even in areas where dolphins are not at risk.
The Government says it will strongly defend the legal action.
Fisheries Minister Jim Anderton accepts livelihoods will be affected, however he says the decisions taken were hard but necessary.
The Department of Conservation classifies Hector's dolphins and Maui's dolphins as nationally critical.