The susceptibility of arctic zooplankton species to small lake trout (Salvelinus namaycush) was investigated by measuring both the reactive distance of fish to prey and the success with which prey were captured. Species common to ponds without fish were found to be more vulnerable to lake trout than lake species, several of which appear to have developed adaptations to reduce visual predation. Key words: lake trout, zooplankton, predation, reactive distance