Fish ectoparasites are introduced to water bodies or aquaculture systems along with their hosts. Argulid fish lice can survive off-host for a given time, and in spite of quarantine measures might also be introduced via the transfer of water. However, they must cope with varying abiotic conditions without access to food. We investigated the effect of temperature (5 to 28oC) on the off-host survival time of Argulus japonicus, an invasive species which is apparently increasing its distribution, and compared this with the European A. foliaceus. A clear effect of temperature on the off-host survival time of all stages of both species was demonstrated. Larval and juvenile A. japonicus survived up to 9 days at 22oC and in the case of adults up to 13 days at 15oC. By comparison, larval A. foliaceus survived up to 5 days at 15oC, adults up to 14 days at 9oC and juveniles up to 7 days at 9oC and 15oC. Thus, A. japonicus is more resistant to starvation at higher temperatures under controlled off-host conditions and A. foliaceus is more resistant to starvation at lower temperatures. Infectivity of A. japonicus decreased linearly with the time spent off-host after 2 days for larvae and 4 days for adults. Temperature only had a significant effect on the infectivity of both developmental stages after 24 hours off-host between 13–23oC for larvae and 13–18oC for adults. In conclusion both species can potentially survive off-host periods in water transports for up to 13–14 days as adults. Their survival is shorter as larvae. This study demonstrates that transportation of water has the potential to introduce Argulus species [Current Zoology 57 (6): 828–835, 2011].