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 CO 2 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 (MO 2 ), MO 2 max, and Ucrit did not differ between ploidies, triploids had a smaller increase in MO 2 over the course of the swimming trial and lower arterial O 2 content (C a O 2 ) 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 (P a O 2 ) and methemoglobin values. Overall, triploids and diploids did not differ in C a CO 2 , P a CO 2 , arterial pH, or lactate at any of the swimming speeds. Taken together, triploidy does not appear to impair CO 2 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.