Distribution of whio on the New Zealand river network

This dataset was used to make predictions of the relative likelihood of whio (<em>Hymenolaimus malacorhynchos</em>) occurrence across the New Zealand river network based on contemporary habitat conditions and prior to human arrival in New Zealand. A brief description of the data is provided below. Whio distribution data Whio data were obtained from a New Zealand Department of Conservation (DOC) database containing 17,113 records of their occurrence in more than 166 river catchments across New Zealand. These data represent presence records collected from 1979–2016 during targeted surveys of river catchments looking for whio and routine monitoring of known whio populations, as well as incidental sightings by DOC staff and citizen scientists. Each whio occurrence record was buffered by 250 m and assigned to the nearest reach of the New Zealand digital river network, a representation of the spatial configuration of New Zealand’s rivers. This network comprises ~576,000 reaches, each representing the length of river between confluences. Where multiple whio occurrence records were assigned to the same reach, they were combined to give a single presence record to avoid pseudo-replication. In all, we identified 5,439 reaches where whio had been observed between January 1979 and January 2016. <br> Predictors Each reach in the digital river network has been characterised by a set of predictors, including catchment area, stream length, elevation and slope derived from digital elevations models; catchment geology derived from geological maps; land cover from remote sensing data; and runoff, rainfall and potential evapotranspiration from interpolated climate station data. We selected predictors from the digital river network likely to be important in structuring whio distribution through physical habitat provision and food availability. These predictors described characteristics of the hydrology, topography, climate and land cover for the entire New Zealand river network at two spatial scales ecologically relevant to whio; the local reach and upstream catchment.