A network of 19 marine parks has been established in South Australia with the aim of protecting the state's environment for future generations.
The network of parks stretches from the state's southeast to the west coast and places restrictions on commercial and recreational fishing.
The parks also include smaller sanctuary zones which will essentially become no-go areas for fishing.
Environmental groups have welcomed the action, with the Wilderness Society describing it as one of the most significant conservation initiatives in the state's history.
However a parliamentary select committee that has been investigating the parks legislation and consultation process says questions remain about their size and the impact on local communities.
Premier Jay Weatherill said South Australians cherished their marine environment.
"Our oceans have more diversity than the Great Barrier Reef and many of the marine plants and animals living in southern Australian waters can't be found anywhere else on earth," he said.
"That is worth protecting."
Environment Minister Paul Caica said the sanctuary zones, where fishing would not be allowed, made up just six per cent of the state's waters.
"These zones allow for preservation, while elsewhere commercial fishers can continue to benefit from harvesting clean, green, premium South Australian seafood," Mr Caica said.
While the park boundaries were declared on Thursday, the fishing restrictions will be phased in over the next two years.
In 2013 the state government will also begin a process of buying back entitlements from commercial fishers adversely affected.
Fisheries Minister Gail Gago said commercial fishing made an important contribution to the state economy and the parks had been designed to avoid productive fishing areas where possible.
Committee chairman, Family First MP Dennis Hood, said it was clear many people believed their future livelihoods were threatened by the sanctuary zones.
"Many fishers believe that South Australia's well-managed fisheries provide the necessary conservation and ecological outcomes without the necessity of such zones," he said.
But Wilderness Society campaign manager Peter Owen said sanctuaries were proven to protect marine life and generate economic and social benefits.
"Sanctuaries are an investment in our future," he said.