Over the past three years, routes which had been predominantly used by seasoned hikers and mountain climbers, had become a hot-spot for tourists and inexperienced trampers, Doc Te Anau operations manager Greg Lind said.
Images of Fiordland's beauty circulating on social media had enticed more people who were unprepared for the possible dangers on the routes, he said.
"They're ... going to these places and participating in the experience without any understanding of what is confronting them in terms of risks."
Israeli tourist Udy Brill, who died on the Gertude Saddle track in 2016, and French woman Anne-Marie Scaglione-Genet, who died in the same area last year, were both experienced trampers.
As a result of the fatalities, Doc installed signs at the head of the Gertrude Valley floor alerting trampers about the hazards of the route, he said.
"They have the information about the skills that you need to go there and the hazards that you're likely to encounter, and the number of fatalities that have taken place there.
"If you stand there and watch people, they pay no attention whatsoever to those signs, by and large - the vast majority will walk straight past them and carry on," he said.
Fatalities in the area had grown "rapidly" in recent years with 11 fatalities in Southland over the 10 years to June 2017, nine of which were in the past four years, Mountain Safety Council chief executive Mike Daisley said.
"The Instagram effect is real.
"People are getting heavily motivated by beautiful scenery - you can see on Instagram what you'd like to go and see yourself - but on [Gertrude Saddle] you're literally having to scale rock cliffs," he said.
While the information was readily available, the challenge was making it known to "vulnerable" trampers who had no contact with Doc or other local organisations, Mr Lind said.
"The real challenge for any agency is to try and intercept them and influence their decision-making."
Doc would go as far as removing images of the Gertrude Valley from its website and brochures, and had also established a visitor safety manager to address the problem on a national scale, he said.
The Mountain Safety Council had released in-depth information to demonstrate and quantify the issues, and would work collectively with other organisations to produce more "targeted tools" to reach vulnerable trampers, Mr Daisley said.
A coroner's report on the deaths of Mr Brill and Mrs Scaglione-Genet was released on Tuesday. In it Coroner Marcus Elliott was critical of Doc and said Mrs Scaglione-Genet's death might have been prevented if Doc had installed route markers at a crucial stream crossing on the Gertrude Saddle, where Mr Brill died in similar circumstances.
