https://www.rnz.co.nz/news/country/491638/invasive-freshwater-gold-clam-well-established-in-waikato-river-before-discovery
The invasive freshwater gold clam discovered in the Waikato River in April had been there for two to three years, the Ministry for Primary Industries says.
freshwater gold clamwell establishedwaikato riverinvasive
https://niwa.co.nz/te-kuwaha-and-maori/report-trends-analysis-selected-indicators-waikato-river-health-and-wellbeing
Report: Trends analysis for selected indicators of Waikato River health and wellbeing 2010-2019
trends analysiswaikato riverreportselectedindicators