Dr Smith's decision was slammed by conservation groups, who said the extension was too small to guarantee the survival of the Maui's dolphin species.
Maui's and Hector's Education/Action group chairwoman Christine Rose said today's protest showed how angry people were about the Government's attitude towards the world's rarest, smallest and loveliest marine dolphin.
"We're angry, but there is hope. We know based on the best scientific evidence that if we remove those human-induced threats from the Maui's habitat, that they can recover to half their 1970 population by 2030. They can recover," Ms Rose said.
Any set-net fishing restrictions around New Zealand also have a large impact on the local fishers. Last month's announcement from Dr Smith meant set nets will now be banned up to 13km offshore between Pariokariwa Pt and the Waiwhakaiho River in Taranaki. This is a 350sq km increase to an area - which runs along the west coast of the North Island from Maunganui Bluff, near Dargaville - already under net restrictions.
The Ministry for Primary Industries estimated the measure would cost New Plymouth fishers $81,000 each year.
Labour MP Ruth Dyson, who was among a group of politicians which met the protest march outside Parliament today, said economic impacts of fishing restrictions needed to be set aside when making conservation decisions about Maui's dolphins.
"This has to be a contest of responsibility where conservation wins."