Oamaru Penguins science and environmental general manager Dr Philippa Agnew said anywhere where extraction stops "you are going to get ecosystem recovery".
But Dr Agnew said it would take years to figure out what impact the reserves would have.
Kāi Tahu and the Department of Conservation (Doc), which will co-manage the network, recently announced it had been given the name Te Au Roa o Te Rakihouia, reflecting ancient voyaging traditions and associations.
Waitaki was a "hot spot" for penguin foraging and the reserve could have spillover benefits, but this would remain to be seen, Dr Agnew said.
The reserve was a "really good start".
"It’s definitely pleasing to see that they have been approved."
Dr Agnew was part of the South-East Marine Protection Forum, which was first established in 2014 to make recommendations paving the way for a network of marine protected areas to be established.
The forum made its final recommendations to the Minister of Conservation and the Minister of Fisheries in 2018 and the marine reserves proposals were announced in October 2023.
