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 fish that are associated with susceptibility to toxic compounds. In laboratory 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 live longer or survive the exposure. Studies of this kind would benefit from the ability to identify living individuals as susceptible, as these individuals could then be used to answer currently unanswerable questions. The purpose of this mini-review is to suggest that post-exposure swim performance can be used to sublethally discriminate between susceptible and resistant individual fish after these fish have been exposed to environmental stressors, particularly heavy metals.