A record number of possums have been caught in a Southland control area, as concerns mount over a council system for tackling the pests.

Details captured in a recent Environment Southland report showed 16 designated possum control areas recorded residual trap catch results of 8.3% during a one-year period, exceeding a 5% target.

One long-standing control area recorded 32.7%, which the council acknowledged was the highest result on record.

The trap catch result shows the percentage of possums caught over 100 nights and provides an estimate for population density.

Councillor Geoffrey Young asked at a Wednesday committee meeting if possum numbers had increased in Southland.

In response, council biosecurity officer animals Raoul Thomas said they had "stepped up big time” outside of control areas, including in Hokonui where there had been a large jump.

“And then you look everywhere to the north, to the west, and certainly to the east at Tokonui - and it’s not good.”

Possum control is the responsibility of landowners in Southland, but the council provides assistance to those who want to get on top of the issue through its Possum Control Areas (PCA) system.

Council manager Michelle Powell told Local Democracy Reporting that once the details of a new control area had been worked through with landowners, the council undertook initial work to set up infrastructure and reduce numbers.

There were 65 possum control areas in Southland which covered more than 420,000ha, but only about a quarter of those were monitored by the organisation each year, Powell said.

A resetting trap, like this one pictured, is one of the tools used to reduce the number of possums in the region. Credit: Environment Southland/Supplied.

A report prepared for Wednesday’s meeting raised questions about the effectiveness of the PCA system and suggested a review be undertaken.

It noted although there had been good support for the programme when it was set up, keeping numbers down had proven tricky in some areas.

“The monitoring results raise broader concerns about the current PCA delivery model.

“In several areas, the level of follow-up control required to consistently meet the SRPMP (Southland Regional Pest Management Plan) target appears to be beyond what can reasonably be achieved through landowner effort alone.”

Council staff were now exploring options for the model and a paper was expected back within two months.

• LDR is local body journalism co-funded by RNZ and NZ On Air.