Almost all anglers along the Mackenzie hydro canals are complying with the rules, a night-time operation by rangers has revealed.

Of 122 anglers spoken to, only one offending individual — a tourist — was found.

The American angler was using a bare hook intentionally separated from the lure, a practice legal in some US states but not authorised in New Zealand.

The Fish &  Game operation took place over one weekend last month.

Central South Island Fish &  Game compliance co-ordinator Hamish Stevens said it was “particularly pleasing” to see a near 100% compliance rate as during similar compliance operations several offences had been detected.

All anglers were found to hold valid sports fishing licences.

A regular ranger presence helped reinforce the rules, detect offending and reassure compliant anglers that “everyone is being held to the same standards”, Mr Stevens said.

It was “great” to have Southland rangers join the team and gain experience at the canals.

“The combined team gave us strong coverage across the fishery during the operation.”

The canal fishery was “one of the most popular trout and salmon fisheries in New Zealand”.

Licensing and regulations were in place to help maintain “sustainable” fish populations.