That meant plenty of trout should be available for anglers in coming years, Mr Osborne said.
Meanwhile, with only weeks to go before opening day on October 1, Fish & Game officer Mark Sherburn said anglers should remember there was still good fishing to be had on lakes that didn't close over winter, such as Rotoma and Rotoehu.
Two to four colours of lead line and a Tassie Devil lure trolled along a drop-off at a slow speed would usually do the trick at this time of year, he said.
He said staff would soon be starting their spring programme of releasing nearly 40,000 fish into the Rotorua lakes.
Further east, at Lake Waikaremoana, an intensive spawning and fisheries monitoring programme has also indicated positive trends, and some "impressive fish numbers".
Licences for the coming season are now on sale.
There are now nine different licence options available, from the premium whole season licence covering New Zealand, to a nine-day Long Break licence and One Day licence for a
single day's fishing.