Recreational snapper anglers should have lighter chilly bins from Tuesday as reduced numbers and increased catch size come into force.
The Ministry for Primary Industries says it will allow a period of adjustment before it starts hooking people with hefty penalties.
The ministry said the initial focus would be on raising awareness about the new rules and infringements would be considered case by case by fishery officers.
A spokeswoman added there would be some leniency in the initial period, with individual officers using their discretion.
"Obviously if someone's massively over the limit then it's a completely different story."
The penalties regime remains the same, ranging from $250 fines to forfeiture of boats, community service and fines of up to $20,000.
Controversially, commercial fishing operators are not affected by the changes, despite already having a smaller 25cm limit.
Auckland fisherman Jason Foord, who has been catching snapper off Auckland for most of his life, said the changes would mean many anglers going home with an empty bucket after a day on the water.
"Around the inner harbour you very seldom get anything that's bigger than 32-33cm. Realistically, you do keep those 28cm fish because you might catch only a couple and if you throw those ones back, you're going home empty-handed."
Foord did not have a problem with the changes if it meant conserving New Zealand's snapper population, but resented that commercial fishers would not be impacted. "How do I explain to my 10-year-old daughter that we've got to throw back a fish when you can buy something even smaller at the supermarket?"
Recreational fishing advocacy group LegaSea, which opposed the changes, said it encouraged the public to comply with the new rules.
"But we note with real disgust that it's business as usual with the commercial fleets," said campaign co-ordinator Adam El-Agez.
"We're constantly getting people saying we want to conserve fish but we don't want to conserve them just so the commercial fishing industry can continue to export them."