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This Article Full Text Full Text (PDF) All Versions of this Article: 295/5/R1631    most recent 90461.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Clark, T. D. Articles by Farrell, A. P. Search for Related Content PubMed PubMed Citation Articles by Clark, T. D. Articles by Farrell, A. P.

COMPARATIVE AND EVOLUTIONARY PHYSIOLOGY

Circulatory limits to oxygen supply during an acute temperature increase in the Chinook salmon (Oncorhynchus tshawytscha)

¹Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada; ²Department of Zoology, University of Gothenburg, Gothenburg, Sweden; ³Department of Zoology, University of British Columbia, Vancouver, Canada; and ⁴Department of Forest Sciences, University of British Columbia, Vancouver, Canada

Submitted 29 May 2008 ; accepted in final form 28 August 2008

This study was undertaken to provide a comprehensive set of data relevant to disclosing the physiological effects and possible oxygen transport limitations in the Chinook salmon (Oncorhynchus tshawytscha) during an acute temperature change. Fish were instrumented with a blood flow probe around the ventral aorta and catheters in the dorsal aorta and sinus venosus. Water temperature was progressively increased from 13°C in steps of 4°C up to 25°C. Cardiac output increased from 29 to 56 ml·min^–1·kg^–1 between 13 and 25°C through an increase in heart rate (58 to 105 beats/min). Systemic vascular resistance was reduced, causing a stable dorsal aortic blood pressure, yet central venous blood pressure increased significantly at 25°C. Oxygen consumption rate increased from 3.4 to 8.7 mg·min^–1·kg^–1 during the temperature increase, although there were signs of anaerobic respiration at 25°C in the form of increased blood lactate and decreased pH. Arterial oxygen partial pressure was maintained during the heat stress, although venous oxygen partial pressure (Pv_O2) and venous oxygen content were significantly reduced. Cardiac arrhythmias were prominent in three of the largest fish (>4 kg) at 25°C. Given the switch to anaerobic metabolism and the observation of cardiac arrhythmias at 25°C, we propose that the cascade of venous oxygen depletion results in a threshold value for Pv_O2 of around 1 kPa. At this point, the oxygen supply to systemic and cardiac tissues is compromised, such that the oxygen-deprived and acidotic myocardium becomes arrhythmic, and blood perfusion through the gills and to the tissues becomes compromised.

blood pressure; blood respiratory properties; cardiac output; hematocrit; hemoglobin; heart rate; blood plasma; rate of oxygen consumption; oxygen equilibrium curves; Pacific salmon; stroke volume; vascular resistance

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