Otago fishermen are breaking the rules regularly and, just over a month into the season, 21 infringement notices have been issued already.
That compared with 27 for the entire season last year.
Fish and Game Otago operations manager Ian Hadland said he was ''mystified'' as to why there was a spike in offences throughout the region.
''The people encountered seemed to know the rules but had just taken the risk of having a quick fish,'' Mr Hadland said.
''Nearly all of them [confessed] to not having a licence.''
Most offences this season were for fishing without a licence.
Two cases were for fishing in a closed area before the season started.
Three people also gave false or misleading information to Fish and Game rangers.
''[Some] offenders were simply naive but ignorance of the regulations is no excuse,'' Mr Hadland said.
''It's annoying that easily avoidable offences are being detected, especially fishing without a licence.''
People caught fishing without a licence could expect a fine of up to $5000, he said.
''I'd sooner spend time teaching the next chap to fish rather than dealing with an offender who should have known better.''
Open seasons in Otago run from October 1, or November 1, for all lakes and rivers and close at the end of either April, May or September.
The Greenstone River upstream of Sly Burn confluence opens on February 1 and closes on March 31.
