Oxygen and carbon dioxide transport during sustained exercise in diploid and triploid chinook salmon (Oncorhynchus tshawytscha)

To better understand the respiratory physiology of triploid fish, we conducted an analysis of O-2 and CO2 transport in diploid and triploid chinook salmon (Oncorhynchus tshawytscha) swimming at 0.4 body lengths (BL).s(-1), at 2.0 BL.s(-1), and at the critical swimming velocity (Ucrit). While O-2 consumption rates (MO2), MO2 max, and Ucrit did not differ between ploidies, triploids had a smaller increase in MO2 over the course of the swimming trial and lower arterial O-2 content (CaO2) values than diploids. Relative to diploids, triploids swimming at Ucrit had a reduced Hb-O-2 saturation, lower red blood cell (RBC) pH, but similar O-2 partial pressures (PaO2) and methemoglobin values. Overall, triploids and diploids did not differ in CaCO2, PaCO2, arterial pH, or lactate at any of the swimming speeds. Taken together, triploidy does not appear to impair CO2 transport or acid-base balance during sustained exercise in chinook salmon. In contrast, our results show that triploids have a smaller O-2 carrying capacity than diploids. While triploids may be able to compensate for their reduced aerobic capacity under the current exercise regime, we suggest that the effects of triploidy on O-2 transport may contribute to the inferior performance of triploid salmon when reared under suboptimal conditions.