Effects of Temperature and Hydrostatic Pressure on Routine Oxygen Uptake of the Bloater ( Coregonus hoyi)

Abstract

We present the first measurements of routine oxygen uptake (VO 2) of the bloater ( Coregonus hoyi), including the effects of temperature and hydrostatic pressure. For temperature experiments, ten 24 hour trials were conducted each at 10.5°C and 7°C, using flow-through respirometry. Average routine VO 2 was approximately 130 mg O 2/(kg*hr) at 10.5°C and approximately 120 mg O 2/(kg*hr) at 7°C. These values did not differ significantly, probably because we used temperatures spanning the thermal range of bloater, within which this species may conserve routine metabolism. Derivations of daily food ration for bloater were calculated and compared with a previous bioenergetics model. For pressure experiments, the diel vertical migrations bloater undertake in the wild were simulated using a flow-through respirometer that could be pressurized. Ten 3-day trials were conducted, consisting of an overnight acclimation to the respirometer, a 12-hour pressure regime, and a day of recovery. The pressure regime involved a compression from 1 atm (atmospheric pressure) to 4 atm over 6 hours and a subsequent decompression of the same magnitude and duration. Increases in hydrostatic pressure elicited a rise in bloater VO 2 and motor activity; conversely, the subsequent decrease in hydrostatic pressure caused a return of oxygen uptake and motor activity to baseline values at 1 atm. We hypothesize that pressure-induced compression of the gas bladder explain the changes in VO 2, because increased swimming (causing increased VO 2) is needed to maintain station when the swimbladder is compressed.