A pest control operation targeting feral goats around State Highway 8 near Cromwell has exceeded expectations.

Sunday morning’s aerial cull in the Cromwell Gorge had a confirmed tally of 225 goats, the NZ Transport Agency Waka Kotahi said.

This was more than expected and the operation had run smoothly in freezing conditions, an agency spokesman said.

Feral goats had been increasing in number in the area, posing a safety risk when they wandered on to or near the road.

As well as creating a higher risk of crashes, the goats damaged vegetation and contributed to erosion on the hillsides above the highway, which could increase rockfall risk, the agency said.

SH8 between Cromwell and the Clyde Dam was closed for an hour from 8am while a cull was carried out by helicopter.

The aerial work was then followed up on the ground.

The agency spokesman said the decision was made to dispose of the carcasses.

"The potential for them to be used for food was considered, however the carcasses are often difficult to access and may be disbursed across steep and difficult terrain.

"In addition to this, there are food safety and public health considerations – the advice from the Ministry for Primary Industries is that “no assurances can be given about whether meat from wild animals is fit to eat”, and it comes with the risk of disease and contaminants.”

Further aerial pest control work is planned in the gorge for the next two Sundays.

Ground control work would be ongoing throughout winter, the agency said.