Physiological Tradeoffs Underlie the Evolution of Hypoxia Tolerance and Exercise Performance in Fish

There is a frequently observed tradeoff between hypoxia tolerance and exercise performance in fish, even though both of these traits are often associated with a high O 2 transport capacity. We examined the physiological basis for this tradeoff in four species of bass and sunfish from the family Centrarchidae. Hypoxia tolerance was greatest in rock bass, intermediate in pumpkinseed sunfish and bluegill sunfish, and lowest in largemouth bass, …