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New Zealand is an archipelago with many islands of conservation significance, none of which has the full suite of invasive vertebrate pests found on mainland New Zealand. Managing invasive species on New Zealand islands involves prevention of pests establishing and controlling or extirpating those already there. Prevention measures, referred to as island biosecurity, focuses on the three major pathways for pests to arrive: deliberate release, accidental release and swimming. Managing deliberate release is largely reactive but does have opportunities for prevention depending on the motivation of offenders. Managing accidental release is where most proactive work is done by Department of Conservation staff to protect remote high-value nature reserve islands. A comprehensive quarantine, surveillance and contingency response system is in place for these sites. When managing self introductions, the size and nature of the water gap and the species involved largely determine the risk. Many islands are beyond the swimming range of all pests, but for some closer ones, we are exploring the feasibility, costs and benefits of managing reinvasion across various water gaps and trying to improve our detection and elimination techniques. Eradication backed up by successful ongoing island biosecurity in many cases compares well with alternative management options at mainland sites.