Lanternfish (family Myctophidae) are small, deep-sea organisms and among the most abundant vertebrates on Earth. They are named for their bioluminescence, utilizing specialized light-producing organs called photophores scattered across their bodies. Found in oceans worldwide, lanternfish possess an immense global biomass, with some estimates suggesting they account for up to 65% of all deep-sea fish biomass. Their sheer numbers and widespread distribution make them a highly significant component of the marine ecosystem. Their size typically ranges from 2 to 30 centimeters in length.
Primary Food Sources
Lanternfish are primarily planktivores, meaning their diet consists of the small organisms that drift in the water column. The most critical component of their diet across various species and ocean regions is copepods, which are tiny crustaceans. Copepods often dominate the stomach contents of lanternfish, sometimes making up more than half of the total volume of food consumed.
The diet is supplemented by other small crustaceans, including euphausiids (a type of small krill) and ostracods (seed shrimp). These small, energy-rich organisms provide the necessary fuel for the lanternfish’s extensive daily migrations. The majority of their food intake is derived from these zooplankton, though the exact composition varies by species, location, and the fish’s life stage.
Smaller or larval lanternfish may feed on tinier planktonic organisms, such as diatoms and ciliates, before shifting to larger prey as they grow. Larger adult lanternfish will occasionally consume small fish larvae and even other smaller myctophids. The high lipid content of their crustacean prey is essential for sustaining the lanternfish’s energetic lifestyle.
Feeding Strategies and Adaptations
The feeding success of lanternfish is tied directly to Diel Vertical Migration (DVM). This synchronized behavior is considered one of the largest migrations of biomass on the planet, involving millions of individuals. As the sun sets, lanternfish ascend hundreds of meters from the mesopelagic zone, or “twilight zone,” to the surface layers of the ocean.
They spend the night feeding in the food-rich epipelagic zone, where zooplankton are abundant and light levels are low, providing cover from visual predators. When dawn approaches, the lanternfish begin their descent back to the deeper, darker waters, typically resting at depths between 300 and 1,500 meters during the day. This behavioral adaptation allows them to maximize feeding opportunities while minimizing the risk of being eaten by predators that hunt in the sunlit surface waters.
Lanternfish possess specific physical traits that enhance their ability to capture prey. Most species have a relatively large mouth compared to their body size, which allows them to engulf a wide range of small, active prey items. They also have fine filtering structures called gill rakers, which function like a sieve to strain small crustaceans from the water. Specialized jaw structures further aid in the capture of fast-moving zooplankton during their brief nightly feeding window.
Role in the Ocean Food Web
The daily feeding and migration pattern of lanternfish positions them as a foundational link in the transfer of energy throughout the ocean. By consuming surface zooplankton at night and descending to the deep ocean during the day, they effectively transfer vast amounts of organic matter and energy to the deep-sea ecosystem. This process is a significant component of the “biological pump,” which moves carbon from the surface layers to the deep ocean.
The carbon and energy they ingest are delivered to the deeper waters through their respiration and the excretion of fast-sinking fecal pellets. This active transport mechanism supports the metabolism of deep-sea organisms that would otherwise have limited access to food resources.
Lanternfish are also a primary food source for a wide array of larger marine predators. Their immense biomass makes them a central part of the diet for commercially important fish, such as tuna, mackerel, and billfish, as well as marine mammals like whales and dolphins, and numerous seabirds. By acting as a dynamic intermediary, lanternfish connect the productive surface waters with the food-scarce deep ocean, making them indispensable to the global marine food web structure.