Early establishment of Corbicula fluminea (Muller, 1774) in Aotearoa-New Zealand; insights from a newly invaded river system

Corbicula fluminea (Müller, 1774), a freshwater bivalve native to eastern Asia, is one of the world's most widespread and impactful aquatic invaders.Its rapid population growth, early maturity, and efficient dispersal have facilitated establishment across the Americas, Africa, and Europe.Here, we present the first data-supported record of C. fluminea establishment in Aotearoa-New Zealand.The species was first detected in April 2023 at Bob's Landing, Lake Karāpiro, within the Waikato River catchment.In June 2023, delimiting surveys were conducted across 25 wadeable sites, including hydro-lakes and riverine stretches, using both physical searches and environmental DNA (eDNA) to assess the extent of the incursion in the Waikato River.Quantitative shoreline monitoring at one of the initial incursion sites (Horahora Reserve, Lake Karāpiro) was undertaken over three consecutive years (2023-2025) to track population development.Densities increased nearly 50-fold, from 27 to 1,360 clams m -2 , accompanied by significant growth and increasing size-class complexity, indicating rapid establishment and recruitment.This study provides the first evidence of C. fluminea establishment in Aotearoa-New Zealand and offers rare insight into the species' early invasion dynamics in a temperate Southern Hemisphere River system.