Sublethal identification of susceptible individuals: Using swim performance to identify susceptible fish while keeping them alive

One branch of ecotoxicology has focused on identifying genetic markers in f ish that are associated with susceptibility to toxic compounds. In laborato ry studies, a common approach has been to compare the genetic variation in fish that die first in time-to-death studies to that found in fish that liv e longer or survive the exposure. Studies of this kind would benefit from t he ability to identify living individuals as susceptible, as these individu als could then be used to answer currently unanswerable questions. The purp ose of this mini-review is to suggest that post-exposure swim performance c an be used to sublethally discriminate between susceptible and resistant in dividual fish after these fish have been exposed to environmental stressors , particularly heavy metals.