Over the past 150 years, trout have been introduced into most of Aotearoa New Zealand’s large and easy‑to‑reach lakes, leaving very few places where native kōaro can live without predators. Fish Future’s PhD student Lauren Hitt, together with Simon Stewart, Nixie Boddy and Angus McIntosh, pulled together national datasets and on‑the‑ground surveys to find lakes, tarns, ponds, and wetlands that still support trout‑free kōaro populations.
What we found is concerning. Many of these habitats are small, isolated, and hard to access, and our knowledge about them is outdated and incomplete. Alarmingly, at least 10% — and possibly up to 22% — of known trout‑free kōaro populations may have disappeared in just the last 20 years.
These remaining populations are likely unique and highly vulnerable, facing growing threats from invasive fish and climate change. Protecting these special lakes is critical to safeguarding kōaro, an important taonga (treasured species), and the richness of Aotearoa’s freshwater biodiversity.