Metabolic responses to hypoxia of Lycenchelys verrillii (wolf eelpout) and Glyptocephalus cynoglossus (witch flounder): Sedentary bottom fishes of the Hatteras/Virginia middle slope

We collected wolf eelpouts Lycenchelys verrillii and witch flounder Glyptocephalus cynoglossus from Hatteras (North Carolina, USA) and Virginia (USA) Middle Slope sites using a submersible, and made shipboard measurements of their respiration rates and survival in hypoxic (<10% O2 saturation) and anoxic conditions. Both species from the Hatteras site reduced their respiration rates as ambient oxygen decreased, but eelpouts from the Virginia site maintained a constant respiration rate until oxygen saturation dropped below 20%. Moreover, eelpouts from the Hatteras site were significantly more tolerant of hypoxic conditions than fish from the Virginia site and survived anoxia for short periods. These results and our submersible observations of fish behavior support the hypothesis that the Hatteras Middle Slope fauna is exposed to short-term hypoxia events.