A BLUE whale’s heart drums at roughly 20 beats per minute, a human heart at 60 to 80 bpm, but eavesdrop on a hummingbird’s tiny ticker and you’ll find more of an incessant whir than a pulse. In birds and mammals, the bigger the animal, the slower its heart. But fish, it turns out, do not follow this law.
There is simply no relationship between their body mass and heart rate, say Timothy Clark and Tony Farrell of the University of British Columbia, Vancouver, Canada. They implanted biologgers in nine wild male Chinook salmon to measure their heart rate…
