Seeking higher calories for Puget Sound killer whales

A 2014 paper decribes how monitoring the energy density of key Pacific salmon species could affect the recovery of northern and southern killer whales through fisheries management.


Southern resident killer whale recovery is dependent upon these animals finding sufficient prey, specifically salmon. This paper, recently published by scientists at NOAA Fisheries and the Washington Department of Fish and Wildlife, evaluates the energy density of 5 different Pacific salmon species, including multiple distinct populations of Chinook salmon, a key salmon species for southern resident killer whales. They show that lipid content, a major contributor to salmon kilocalories and therefore energy for killer whales eating them, is related to migration length and elevation. Specifically, coastal salmon (ones that migrate shorter distances up river) have a lipid content of 2-5% whereas this jumps to 12-15% for interior spawning populations that have to migrate further upstream before spawning. As one would expect, the larger the salmon, the more total energy they provide to killer whales consuming them, and large fish size offsets salmon energy density in determining their total energy value. A killer whale would need to eat approximately 2.7 coho, 3.1 chum, 3.1 sockeye or 6.4 pink salmon to obtain the equivalent total energy value of 1 Chinook salmon. These data will aid managers in determining the benefit of salmon fishery closures, by salmon species and for specific populations within a species, to southern resident killer whales. -- Summary description by Joe Gaydos for the Encyclopedia of Puget Sound.


O’Neill, S. M., Ylitalo, G. M., & West, J. E. (2014). Energy content of Pacific salmon as prey of northern and southern resident killer whales. Endangered Species Research, 25, 265–28.