The First Warm-Blooded Fish Ever Discovered May Be a Fish People Have Been Eating for Centuries (or More)

by Owen James Burke

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A red, tropical, or Hawaiian, moonfish. Image: Zazzle.

They’ve been adorning plates for ages, but the Hawaiian moonfish (Lampris guttatus) has only recently been discovered to be the first fully warm-blooded fish ever studied, according to a recent report in the journal Science.


Photo: NOAA.

“The opah appears to produce the majority of its heat by constantly flapping its pectoral fins which are used in continuous swimming,” study leader and biologist at NOAA’s Fisheries’ Southwest Fisheries Science Center in La Jolla, California, Nicholas Wegner told LiveScience.


Photo: NOAA.

NOAA’s team of researchers tagged and tracked a Hawaiian opah for eight months, finding it at mostly around a depth of 150 feet. But, when it did dive, it’s body temperature regularly remained 41° Fahrenheit (5° Celsius) warmer than the water around it.

Still, not everyone buys that the fish is fully endothermic. Diego Bernal, an associate professor of biology at the University of Massachusetts Dartmouth, tells The Washington Post that the Hawaiian opah doesn’t maintain the higher temperature evenly throughout its body, and like some other fish, is only “regionally endothermic.”

Little else is known about the opah. It’s caught in depths of up to 1,300 feet, but is far from an everyday haul, so they’re difficult to study, and marine biologists have no real way of estimating their populations. Next, Wegner says he and his team plan to study the blue opah (Lampris immaculatus), the tropical red opah’s cold water cousin.

Read more at LiveScience. -OJB

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