He said the fish released were about a year old and measured about 18cm.
"Within a year in the lake they will grow to a good catchable size," he said.
While there is no size restriction on the trout caught in Lake McLaren most licensed anglers were not interested in keeping such small fish, he said.
Mr Tomson said Lake McLaren was a popular spot for Tauranga anglers to take their families.
"It's a great place just to get kids involved in fishing. It's a good place to go up there and have a picnic and teach your kids about the outdoors," he said. "We try to treat the fishing out there as a bit of a catch and release so that future generations can enjoy it. We just take the odd fish here and there."