Fish & Game field officer Paul van Klink said six signs were ripped off posts and most of them taken were for a voluntary beat system along more than 20km of the river.
Another field officer discovered the vandalism and theft yesterday while doing maintenance on a previously damaged sign.
A voluntary beat system was introduced in the Nevis River at the start of the 2020-21 fishing season, following concerns about angling pressure there.
"We put in the beat system for anglers’ enjoyment by spreading them out along the river to minimise contact," Mr van Klink said.
"Feedback about the system has been overwhelmingly positive."
The Nevis River is a brown trout fishery.
Anglers were expected to park their vehicles next to a beat sign and
leave their intentions on their dashboard.
Other anglers could fish behind on the same beat.
Mr van Klink asked anyone with information about the vandalism to contact either Otago Fish & Game or police.
Anyone who was unhappy with the system was welcome to talk to Fish & Game directly about it, he said.
