Otago Peninsula Biodiversity Group aims to eradicate animal pests on the peninsula in an effort to improve the peninsula's biodiversity.
Since March, pest contractors had been poisoning and trapping across about 4000ha north of Portobello including Taiaroa Head and Cape Saunders.
Group project manager Richard Wilson said the initial "knock-down" stage of the programme ended last month with 2800 possums killed by contractors.
While it was difficult to calculate possum numbers, it had been estimated there were 10,000 across the 10,000ha peninsula, he said.
Certain areas had denser populations, such as the 50ha bush section on Taiaroa Head where about 650 possums were killed and Okia reserve where 500 were killed.
The process had also highlighted the high numbers of feral cats in the area, he said.
He was pleased no issues arose from the programme, which used cyanide bait and traps, given the sensitivity about poisoning programmes.
In a few months, the monitoring lines would be checked and wax tags which possums bite, leaving teeth marks, would be put out so more targeted programmes could be implemented to keep numbers down, he said.
The group was also setting up a "hotline" so people could report sightings of possums.
Sixteen sites would be monitored to see how the vegetation recovered without possums browsing, and 24 1km bird transects would also be monitored by volunteers to see if there was any change in bird life.
Next, the group planned to go to the communities from Portobello to the city offering 400 traps for people to use on their properties to help tackle the "huge number" of possums on the northwest faces of the peninsula, Mr Wilson said.
It was also fundraising to begin a similar knock-down programme on the main part of the peninsula.
