Killer Whales are Picky Eaters

A killer whale's favorite meal is king salmon, according to a new study that found these predators scan wide ocean regions listening for their favorite fish. Echolocation, which involves creating a sound in order to produce an echo, allows the whales to zone in on king salmon, also known as Chinook salmon, at distances up to half a mile.

But why do killer whales go to so much trouble to hunt down king salmon, picking them out even when they represent just 5-10% of the available salmon population? Because salmon are not equally nutritious -- Chinook salmon have the highest concentration of lipids, or fats, that the whales seem to prefer.

Although these fish look similar to human eyes, the study showed the echo structure created by each type of salmon was unique and could be used by killer whales to discriminate among the various species. "Fish gas" appears key to the process, as the study revealed echolocation tuned especially well into information released by each salmon's swim bladder. Swim bladders are gas bags within a fish that help the fish to be buoyant at any specific depth. They are probably the best reflector of acoustic energy underwater.

Original article here.