Ministry inshore manager Leigh Mitchell announced the commercial fishing season would now open on June 1 and close on November 19.
Previously, the season opened on June 21.
"This change will give commercial fishers a little more flexibility to structure their fishing operations around when rock lobster prices in overseas markets are at their highest," Ms Mitchell said.
However, rather than increase profits, CRA7 spokesman Roger Bartlett believed it could significantly affect the rock lobster population in Otago.
"I'm absolutely aghast at the complete stupidity of the decision," Mr Bartlett said. "It's a bungled decision."
Mr Bartlett did not believe the extra days would actually give commercial fishers the ability to take advantage of higher rock lobster prices in overseas markets.
He said the prices were only high at certain times of the year because the availability of rock lobster was more restricted.
If more was available then, prices would drop, he said.
Mr Bartlett said the Otago rock lobster fishery stretched from the Waitaki River south to Long Point, but due to the quota management system introduced in the 1980s, rock lobster fishermen could catch only a total of 189 tonnes between them.
"Having an extended season may encourage fishers to catch more smaller lobster rather than take the time to gather fewer larger lobster in an effort to fulfil their quotas.
"It's going to eat into our stocks, which may affect the sustainability of the fishery. Once it's gone, it's gone," he said.
In explaining the ministry's decision, Ms Mitchell said "non-commercial fishers say one of their best fishing times is autumn when the weather is settled and the sea calm".
"The commercial fishery will remain closed over autumn so the slightly longer commercial season should have minimal impact on non-commercial fishing."
She admitted the recreational and commercial fishing sectors were divided on whether the commercial season should be extended.
The small extension would not give either sector exactly what they wanted.
Instead, it would provide a good balance between meeting what both recreational and commercial fishers want, Ms Mitchell said.
Last year, rock lobster exported from New Zealand was worth more than $68 a kilogram, which gave the Otago rock lobster fishery an estimated export value of about $8.2 million.
Fiordland Lobster processes most of Otago's lobster from its new factory at Sawyers Bay.
Its chief executive, Mike Schuck, said the change would cost fishermen in Otago millions in lost earnings and meant they would have to catch lobster when they could, rather than when lobster was at its best or when there was the best price.
There were already concerns from Japan about the quality of lobster being caught, resulting in one Japanese client - Maruyoshi Suisan owner Kyoichi Yoshizuka - visiting New Zealand to see the situation first hand, he said.
The industry had been working hard for years to get Otago's unique seven-month season extended to year round or at least from April to November, Mr Schuck said.
"This decision is useless."
