Cannabis recovered in the aerial operation in the top of the south.

Police have netted 9000 cannabis plants in the annual aerial recovery operation in the top of the South and West Coast.

About 6000 plants were recovered in the Nelson-Marlborough area of the Tasman police district and more than 3000 on the West Coast.

Operation commander Senior Sergeant Grant Andrews said the number of plants recovered was a significant increase on last year's result. Reports last year estimated about 4000 plants had been recovered across the district.

Andrews said officers located some large commercial outdoor plots along with a number of indoor growing operations.

"It's a success in the fact we have removed that much cannabis," he said.

As a result 13 people face a range of drug and firearms charges.

While the aerial phase has been completed, Senior Sergeant Andrews said there was still a lot of work to be done following up on information gathered and further arrests were likely.

"It's not over just because the helicopter is no longer here," he said.

"This is a year-long operation and a significant part of the operation is gathering and checking information we receive from the public. I'd like to thank all of the people who have come forward with information about drug related activity as they have greatly assisted this operation. Those people are actively helping to keep their communities safe and without that partnership our job would be significantly harder."

He encouraged anyone with information or concerns to contact their local police.

The police aerial operation was assisted by the Royal New Zealand Airforce with a NH90 helicopter that enabled staff to reach difficult to access areas.