Susceptibility of the Antarctic fish Pagothenia borchgrevinki to MS-222 anaesthesia

Summary Induction of anaesthesia and distribution of the routinely used fish anaesthetic, MS-222 (ethyl m-amino-benzoate methanesulfonate), were monitored in the Antarctic fish Pagothenia borchgrevinki. As expected from the extreme low metabolic rate of Antarctic fish, induction times were significantly longer than those from rainbow trout. Onset of anaesthesia in the Antarctic fish also failed to correlate with either brain or blood MS-222 concentrations, in contrast to the trends observed in freshwater salmonids. High levels of free MS-222 in liver and in the aglomerular kidney, and the presence of acetylated derivatives in the blood, suggest these organs as primary sites of drug metabolism. MS-222 anaesthesia in P. borchgrevinki is also accompanied by dose-dependent changes in haematological parameters.