The gold clams, Corbicula fluminea (Müller, 1774) and Corbicula australis (Deshayes, 1830) invade Aotearoa New Zealand; first records, biosecurity responses and potential long-term ecological impacts

The gold / Asian clam (Bivalvia: Cyrenidae) Corbicula fluminea was first detected in the North Island of Aotearoa New Zealand in May 2023.C. fluminea which is native to eastern Asia, was detected in the Waikato River, the longest river in Aotearoa New Zealand, which drains Lake Taup, Australasia's largest lake.Subsequently, in March 2024, another "gold clam" species, Corbicula australis, native to Australia, was detected in a man-made lagoon, immediately adjacent to the Waikato River.The population structures of both species, with adults and juveniles present in large numbers, indicate both had been present for several years before first detection.A delimiting survey of C. fluminea in the Waikato indicated that the riverine population was significantly more widespread than the initial detection site, unlike C. australis which still appears restricted to the lagoon.Despite this, C. fluminea has not been detected within Lake Taup or outside the Waikato catchment.Future plans involve a management strategy targeting containment within the Waikato catchment, along with continued long-term surveillance efforts.The documented worldwide impacts of C. fluminea as an "ecosystem-engineer", its ability to thrive in a broad variety of environmental conditions, high reproductive potential and the apparently vacant niche ready to be exploited (with few resident competitors or predators), all indicate it could have the greatest impact of any known freshwater animal invader in Aotearoa New Zealand so far.The long-term impacts of C. fluminea in Aotearoa New Zealand will ultimately be determined by how effective management efforts, involving both government and non-governmental entities, are at restricting its distribution and protecting native ecosystems from new incursions.