Study: This is Why Ocean Sunfish Like to Sunbathe
Photo credit: BBC News
Have you ever seen an ocean sunfish? That face is not something you’re likely to forget.
It’s sheer size also leaves an impression; they’re the largest bony fish in the world ranging from three to 10 feet in width and weighing up to 2,200 pounds!
They’re called sunfish because they spend hours each day basking in the sunlight, floating motionless at the ocean’s surface. Scientists just thought this sunbathing action was just sunbathing, but we now know why.
Photo credit: BBC News
According to new research, the sunfish prey on marine hydrozoans – which are kind of like jellyfish. After hunting them at depth, they head to the surface to increase their body temperature using the sun’s rays.
Itsumi Nakamura of the University of Tokyo, Japan led a team that caught several sunfish around Funakoshi Bay and attached cameras with lights and thermometers to measure changes in their body temperatures.
Those instruments naturally separated from the sunfish after four days and returned data to the team. Here’s what they learned:
– The sunfish swam back and forth between the surface and deep water during the day.
– Those diving cycles helped them maximize foraging time.
– Sunbathing helps regulate their body temperature.
– The warming process takes less time than you’d imagine.
Photo credit: BBC News
“Beyond our assumption, their body temperature increased rapidly during surface warming, suggesting they have some physiological mechanisms to increase heat gain from the surrounding water,” Nakamura told BBC News. “This explains why larger sunfish can forage for longer.”
This research may also point to why the sunfish are so big. A large body helps them adapt to their hunting environment because they lose heat slowly.
The discovery is a reminder that the deep sea is “still a frontier” said Nakamura, and increasing observation of the ocean depths is the only way to unlock it secrets.
Curious? Learn more about this fish from BBC News.
