Remote intramuscular injection of immobilising drugs into fish using a laser-aimed underwater dart gun

Department of Biology, University of Victoria, British Columbia, Canada.

Sixty coldwater and warmwater fish ranging in weight from 2 to 35 kg were injected intramuscularly with the hypnotics alphaxalone-alphadolone and metomidate hydrochloride and the non-depolarising muscle relaxant gallamine triethiodide using a laser-aimed underwater dart gun. Alphaxalone-alphadolone produced sufficient sedation for easy netting within five to 20 minutes at doses between 0.3 and 0.5 ml/kg, with induction being somewhat faster in warmwater species. The pattern of induction was similar with metomidate but required doses of 40 to 60 mg/kg. The muscle relaxant gallamine triethiodide showed promise as a practical agent for the capture and handling of large fish by virtue of its smooth induction of paralysis at doses between 1 and 3 mg/kg and its reversible supplementation with orally administered metomidate hydrochloride.