New computer modelling has transformed the understanding of where trout and salmon spawn across Otago.
The system comes into play after generations of rangers and officers put in the legwork all over the region’s river system.
The new modelling predicts 25% of Otago’s rivers and streams are likely to sustain trout and salmon spawning.
Otago Fish & Game officer Jayde Couper said the model was a big step forward in their ability to monitor and manage critical trout and salmon habitats across Otago.
"Ground testing over last summer showed a high level of accuracy, and while not perfect, this model will improve as we gather more data - now we have a very good idea where to look [for spawn points]."
One spawn spot the system managed to identify was a previously unsurveyed tributary in the Catlins River, which was spotted by an early version of the model.
The model was based on extensive datasets, including the Otago Fish & Game spawning database and the New Zealand Freshwater Fish Database.
The model uses habitat conditions which currently support spawning.
It then looks for similar habitat conditions and each section of Otago waterways on its likelihood of supporting spawning.
Staff would be able to double check or update spawning area records dating back 50 years, Mr Couper said.
Fish & Game surveyed over 120km of rivers to test the modelling, with 30km done on foot and the remainder surveyed from a helicopter funded by Contact Energy.
In Otago, brown trout and salmon generally spawn in late autumn and early winter, while rainbow trout spawn from late winter to spring.
