These tiny, glowing fish once tricked scientists into thinking the ocean floor had risen.

Nature · Published 30 September 2026 Swipe more like this →

In short: Lanternfish are the most abundant vertebrates in the deep sea, comprising 60 percent of all deep-ocean fish. Their massive, nightly migration to the surface is so dense that it once appeared as a solid, shifting seafloor on sonar, baffling oceanographers who thought the bottom of the sea was moving.

Belonging to the family Myctophidae, lanternfish are small, mesopelagic creatures named for the bioluminescent organs, or photophores, that line their bodies. These organs produce a cold, chemically efficient light through a reaction that converts chemical energy directly into radiant energy. While some species remain in the depths, many perform a daily vertical migration, rising from the twilight zone to the surface at night to feed on zooplankton before descending again by daybreak.

The light produced by these photophores serves multiple survival functions. By emitting light from their ventral surfaces, lanternfish practice counterillumination, matching the intensity of sunlight from above to mask their silhouettes from predators lurking below. Beyond camouflage, the unique, species-specific patterns of these lights likely facilitate communication, acting as a biological dating app that helps individuals identify mates in the pitch-black ocean. This signaling is critical, as the family contains over 245 distinct species.

The sheer scale of these fish is staggering. Estimates suggest they account for roughly 600 million tons of biomass globally. This abundance makes them a vital link in the marine food web, serving as a primary food source for whales, dolphins, penguins, and large predatory fish. Their presence is so significant that their gas-filled swim bladders create a 'false bottom' on sonar, a phenomenon that perplexed researchers in the 1950s until they realized the signal was actually a massive, migrating school of fish.

Despite their remote habitat, lanternfish are not untouched by human activity. They are increasingly targeted by commercial fisheries in regions like the waters between South Africa and Antarctica. Furthermore, they are inadvertently consuming human waste; researchers have discovered individual lanternfish with over 80 pieces of plastic debris in their guts, highlighting the far-reaching impact of ocean pollution on even the most populous deep-sea species.

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