Mr van Dorp said that poaching during the spawning season was more prevalent in some years than others and it was something Fish & Game worked hard to detect using equipment such as hidden cameras.
"Those who fish without a licence or commit other offences impact on the experience of law abiding anglers and on a user pays basis impose additional costs on those who did the right thing and bought a licence."
Offences are dealt with in a variety of ways including prosecution in court and other informal ways as appropriate.
Last year's precedent-setting case where a trout poacher who took spawning fish was jailed for 6 months remains the most significant penalty to date.
His co-offender David Pake Leef failed to appear in court for sentencing and a warrant was issued for his arrest which to date is still valid.
"If you have any information on Leef please notify us or the police." Mr van Dorp said.
Meanwhile anglers from as far afield as Whangarei have turned out to enjoy a "positive" opening of celebrated Rotorua trout streams on the first day of summer - but Fish & Game say the best is yet to come.
Lake Rotorua tributaries, including the upper Ngongotaha Stream which have been closed over the spawning season, re-opened for summer angling Tuesday morning.
Fish & Game staff who turned out to survey anglers said some caught around six to eight fish over the course of the morning, with more rainbows landed than brown trout.
"It was a positive opening with plenty of fish there to catch, and anglers had lots of room to move up and down the stream," said Fish & Game officer Matt Osborne.
"It's coming to the end of the rainbow spawning run, and browns are only just starting their summer escape from Lake Rotorua's increasing water temperatures. When the lake hits 19 C it's a real trigger and brown trout will bolt up the streams in search of cooler waters and Rotorua is just reaching that figure now," he said.
Trout are trapped part way up the Ngongotaha Stream to be weighed and measured before being set free to continue their travels.
Over ten nights 14 rainbows were weighed in, averaging just over 2kg with the biggest 3.5kg and 62 centimetres long, "the biggest we've seen in a while up the Ngongotaha."
The biggest brown trout was a 5kg female with the average brown size 3.25kg.
Mr Osborne said the number of fish trapped (103 browns and 14 rainbows) and their good condition bodes well for summer fishing.
"Their improving condition reflects improvements in Lake Rotorua's water quality."
