Photo Credit: BBC
Lanternfish are the most common deep sea fish (they make up about 65% of all deep-sea fish biomass!), but are also found all over the world, including in the Puget Sound. They get there name from their luminous glow, which is caused by tiny organs called photophores. The photophores’ arrangement on the side of the fish can tell you the species and gender. They may also play a role in communication such as schooling and courtship. The fish pictured above is a blue lanternfish.
Blue lanternfish like the Puget Sound because it combines deep trenches with areas rich in zooplankton, their main food source. The fish stay in the depths during the day and then migrate vertically to the surface to feed on the plankton at night. To maintain their position in the water column, lanternfish adjust the pressure of their swim bladders, a gas filled organ common to bony fish. Fun fact about their swim bladder: lanternfish caused early oceanographers to mistake where the sea floor was because when they grouped together their swim bladders looked like a solid mass on solar scans!