Code for - An urban Taonga: The distribution and abundance of tuna in urban streams across Tāmaki Makaurau

Freshwater eels of the Anguilla genus are experiencing global declines, largely driven by anthropogenic pressures associated with global environmental change. In Aotearoa New Zealand, tuna (both shortfin and longfin eels) are similarly affected, with habitat fragmentation and modification identified as key contributors to their decline.
To investigate spatial patterns in tuna distribution across an urbanisation gradient, we developed species distribution models (SDMs) using boosted regression trees for streams in the Tāmaki Makaurau (Auckland) region. These models incorporate a range of environmental and anthropogenic variables, including stream hydromorphology, barriers to movement, urban land use, elevation, and distance to the coast.
This repository contains the data and R code used to develop, evaluate, and visualise these models. The SDMs performed poorly, reflecting the complex life-history of tuna and the limitations with the scale of the model. This code provides a transparent account of the modelling process.