“What do eels eat?” sounds like a question with one answer, but eels are a big group, about 1,000 species, and they’ve found ways to eat almost everything that moves on a reef or in a river. Some ambush fish from holes, some crush crabs, some never chase anything at all and just pick plankton out of the passing water. Here’s how the main groups feed, what they eat at each life stage, and, since people ask this too, what eats eels.

What do moray eels eat?

Fish, octopus and crustaceans, mostly caught at night by smell.

Moray eels (family Muraenidae, about 200 species) are the top predators of many reef crevices. During the day most of them sit in holes with their heads out, and after dark many leave their dens to hunt across the reef. Their eyes are small and their eyesight is poor, but their sense of smell is excellent. Each moray has two pairs of nostrils, the front pair on little tubes at the tip of the snout, and it uses them to track prey hiding in cracks and under ledges.

Fish-eating morays such as the giant moray and the green moray have long, needle-like teeth that point backward to hold slippery prey. Their diet is mostly reef fish, along with octopus and squid. Once a moray has a fish in its front jaws, it uses a second set of jaws in its throat, the pharyngeal jaws, which shoot forward and drag the prey down. Our page on the moray eel skull explains how that works.

Other morays are shell crushers. The zebra moray and the snowflake moray have blunt, pebble-like teeth instead of fangs, and they feed mainly on crabs, shrimp and other hard-shelled animals. In the Red Sea, giant morays even hunt as a team with roving coral groupers: the eel flushes fish out of holes and the grouper grabs the ones that escape. You can read more about moray behaviour in our moray eel guide.

What do conger eels eat?

Almost anything they can fit in their mouths.

Congers are big, powerful eels of rocky reefs and wrecks. The European conger can grow past 2 m, and it feeds at night on fish, crabs, lobsters, octopus, squid and cuttlefish. Congers are also scavengers and are quick to find dead fish, which is why anglers catch them on fish baits. A large conger in a wreck can be one of the main predators there. See our conger eel page for more on their habits. Like freshwater eels, congers stop eating altogether when they mature and head offshore to spawn.

What do garden eels and snake eels eat?

Two eels that live in sand, with very different menus.

Garden eels are filter-pickers. They stay anchored in burrows on sandy slopes and rise up into the current, facing upstream, to pick off individual zooplankton such as copepods, fish eggs and tiny larvae as they drift past. Colonies form only where the current reliably brings food. They never chase anything. See garden eels.

Snake eels are ambush and stalk predators. They bury themselves in sand with only the head showing and grab small fish, shrimp and crabs that come close. At night some species leave the sand and hunt across open flats, probing holes with the snout. The spotted snake eel is a typical Atlantic example.

What do American eels and other freshwater eels eat?

Freshwater eels are opportunists that eat more as they grow.

The American eel (Anguilla rostrata) and its relatives in Europe, Asia and the Pacific are generalists. Young eels (elvers) eat aquatic insect larvae, small worms and tiny crustaceans. As they grow into yellow eels they move up to crayfish, snails, mussels, bigger insects, frogs and fish. They’re mainly nocturnal, hunting along the bottom by smell, and they’ll eat dead animals readily. Large female eels can be important predators in rivers and ponds. Freshwater eels sometimes eat other eels, too.

Bigger species follow the same pattern on a larger scale. The giant mottled eel of the Indo-Pacific eats fish, crabs, frogs and almost anything else it can catch. One thing all freshwater eels share is that they stop eating completely when they turn into silver eels and begin their migration to sea. From then on they live off stored fat. Our eel life cycle guide explains that change.

What do baby eels eat?

Not what you’d expect.

Most fish larvae eat live plankton. Eel larvae, the flat, transparent leptocephali, seem to be different. Studies of their gut contents have found mostly marine snow: clumps of dead plankton, faecal pellets, mucus and other organic debris drifting down through the water. That may help explain why leptocephali can grow so large and live for so long as larvae. It also makes them very hard to raise in captivity, because nobody has found an easy way to reproduce their natural food in a hatchery.

What eats eels?

Eels are predators, but plenty of animals eat them.

On coral reefs, adult morays have few enemies. Large groupers, barracuda, sharks and sea snakes are among the few that take them. Smaller eels and juveniles are eaten by many reef predators. Snake eels have a remarkable defence: when swallowed alive they can drive their hard, pointed tails through the predator’s stomach wall, although many die trapped inside the predator’s body.

In rivers and estuaries, freshwater eels are eaten by herons, cormorants, ospreys, otters, larger fish such as striped bass, and seals. The eel larvae and glass eels drifting toward the coast are food for a huge range of fish and seabirds, and only a small fraction survive.

And then there are people. Eels have been eaten in Europe and Asia for thousands of years, from jellied eel in London to grilled unagi in Japan. Demand for eel has driven heavy fishing of glass eels for farms, and it’s a big part of why the European eel is Critically Endangered. Our page on whether you can eat eel covers the food side, including why large morays can carry ciguatera toxin and why eel is never eaten raw.

How eels find their food

Smell does most of the work.

Eels have one of the most sensitive noses of any fish. The European eel’s sense of smell is often compared with a dog’s, and morays rely on smell far more than on sight. They also detect vibrations through the lateral line, a sensory system that runs along the body and picks up movement in the water. That’s why most eels can hunt in total darkness, in murky rivers or deep inside a reef at night, and why a diver waving a fish-scented hand near a moray’s hole is asking for trouble. Our page on eel bites explains how most bites happen.

If you want to watch eels feed in the wild, a night dive is the best bet. Many of the reefs in my dive guides, including the Benwood wreck off Key Largo, which is a popular night dive with morays in residence, become hunting grounds after dark. Keep your torch off the eel’s eyes, stay still and let it go about its business.

How much do eels eat?

Less often than you might think.

Eels are cold-blooded and many of them spend long hours resting, so they don’t need to eat every day. A moray may take a single large meal and then sit in its hole for days while it digests. Freshwater eels feed heavily in the warm months and slow down or stop in cold water, when some bury themselves in mud for the winter. Growth rates follow the food supply: eels in warm, productive water grow quickly and may mature in a few years, while eels in cold, poor water can take decades to reach the same size.

Diet also changes with size. A small moray or elver eats small prey, and the menu expands as the eel’s mouth gets bigger. The largest morays and congers can take fish that would surprise most divers, and a moray’s ability to tie its body into a knot gives it the leverage to tear pieces off prey too big to swallow whole. Some eels are also opportunistic thieves, snatching fish speared by divers or bait from anglers’ hooks.