The policy of conserving endangered species by translocation to protected islands creates many problems, which are here analysed using the example of the European mink (Mustela lutreola). Ten years after the first release of European mink onto Kunashir Island (southern‐most of the Kuril Islands, located off the north‐east coast of Hokkaido), there is still no information on the effects of the new arrivals on the biodiversity of the island. No effort had been made to determine which of the available islands would be least affected by the introduction. The use of islands for the conservation of rare animal species has many important restrictions. Long before any introduction of alien biota to a natural ecosystem, the proposed release site must be thoroughly examined and all possible alternative sites considered.