Victim Support had been asked to assist police in offering the victims the support they need.
"I want to reassure tourists and our local residents that we have a person in custody and are carrying out a thorough investigation.
"The community has trust and confidence in the local police and know complaints will be taken seriously and police will do something about it," Mr Johnston said.
"The local community welcomes and values the many tourists it gets in the Far North. These are very unusual allegations and we will not let them impact on the reputation of a region known for being a favourite destination for overseas visitors." Police particularly want to speak with anyone who stayed in the owner's residence of the Main Street Lodge during the past two-and-a-half years.
Northland tourism leader Jeroen Jongejans said it was disappointing the alleged offending had happened in Northland but expected it would not impact on the region's tourism industry for the coming summer season.
In March Tourism NZ figures showed tourists dropped $600 million into Northland in 2013 making it the second biggest earner for the region behind farming.
At the same time the region was named AA Traveller Monitor's top summer spot and Tourism NZ's fifth most popular popular holiday destination.
Mr Jongejans, a board member with the Tourism Industry Association NZ and co-owner of Dive Tutukaka, said those working in the region's tourism industry strived to provide safe experiences for visitors.
"Every now and then some people managed to slide under the radar and ruin the reputation for 99.9 per cent of excellent businesses.
"It's good that this man is being investigated, it's being dealt with by police now," Mr Jongejans said.
He praised the actions of the judge who declined name suppression during Wednesday's court hearing.
"It's good to have his name out there so there is no guessing as to who it is."
Websites in America, Australia, England and Europe have featured the story. Most of the victims are thought to have been from Germany. The first of the incidents allegedly happened in 2012, the last just this week.