Several methods of euthanasia have been used in fish including hypothermia, electrocution, overdosing with tricaine or carbon dioxide, and a sharp blow to the head. Of these, tricaine administered at 500 mg/L is most desirable as it does not alter blood cortisol, catecholamine, or glucose levels commonly associated with stress (Harrell 1992). Where chemicals may alter experimental data, cranial concussion followed by some other physical method may be employed (Andrews 1993).