Eels are long, snake-like fish that live in rivers, lakes, and oceans around the world. If you’ve wondered what eats eels, you’re not alone! Eels play an important role in aquatic ecosystems as both predator and prey.
If you’re short on time, here’s a quick answer to your question: fish, birds, marine mammals, and even other eels are the main predators of eels. Larger fish species like tuna, grouper, and sharks are some of the most common eel predators.
In this comprehensive article, we’ll take a deep dive into the many animals that prey on eels at different stages of their lives. You’ll learn about the specific species that target eels, where these predator-prey interactions take place, and some interesting facts about how eels try to avoid becoming a meal.
Fish That Eat Eels
Bass
Largemouth bass are aggressive predators that will eat just about anything they can fit in their large mouths, including eels. They often hunt for eels in shallow, vegetated areas and ambush them. With their powerful jaws and sharp teeth, bass can easily capture and consume good-sized eels.
In fact, eels are a prime source of nutrition for bass due to their high fat content. Anglers routinely use eels as live bait to catch trophy bass.
Catfish
Catfish are omnivorous bottom feeders that will eagerly gobble up any eels they come across. Channel catfish, blue catfish, and flathead catfish are all known to hunt and feast on eels, especially in rivers and lakes.
Catfish have very keen senses of smell and taste that allow them to root out hiding eels. They will use their barbels to detect chemicals emitted by eels and then vacuum them up with their large mouths.
Eels provide catfish with a substantial meal full of protein and calories to sustain their large bodies.
Eelpout
Eelpouts are carnivorous fish that belong to the cod family. They inhabit cold, deep waters throughout the northern hemisphere. Despite their name, eelpouts actually prey heavily on eels. Their slender bodies allow them to hunt in cracks and crevices where eels like to hide.
Eelpouts have very large mouths with sharp teeth, enabling them to grab eels and swallow them whole. Their voracious appetite for eels likely led to their “eel” moniker. A single eelpout can devour dozens of small eels in a day.
Tuna
Many species of tuna will eat eels as part of their diverse diet. Bluefin tuna, yellowfin tuna, and albacore are open ocean predators that hunt a wide variety of fish and cephalopods. When available, they will readily consume any eels they come across.
Tunas are extremely fast swimmers, capable of speeds over 40 mph. Once they’ve targeted an eel, it stands little chance of escape. With their large size and powerful jaws, tunas can make quick work of swallowing even big eels whole.
Grouper
Groupers are large bottom dwelling fish that will eat just about any prey they can capture, eels included. Their huge mouths allow them to inhale eels with ease. Groupers have sharp conical teeth designed for holding onto slippery prey like eels.
They lie in wait around structure and ambush any eels that pass by. Groupers have incredibly high levels of strength in their jaws that allow them to bite through eels and break their spines. They represent a formidable predator for eels of all sizes.
Sharks
As apex ocean predators, sharks will feed on eels when the opportunity presents itself. Species like bull sharks, tiger sharks, and great white sharks have all been known to eat eels. Their keen sense of smell allows them to detect eels from great distances.
Once they’ve locked on, sharks use their speed and razor-sharp teeth to capture eel prey. Large sharks can swallow eels whole while smaller sharks will tear them into bite-sized chunks. Very few eels would stand a chance against a full grown shark in attack mode due to the shark’s size and power advantage.
Birds That Prey on Eels
Herons
Herons are known for their skill in hunting and catching eels. These large wading birds often stand completely still at the edge of rivers, lakes or wetlands waiting for an eel to swim by. When an eel is in range, the heron will strike with lightning speed, stabbing the eel with its sharp beak.
Species like the great blue heron and grey heron are especially adept eel hunters. In fact, eels can make up a substantial part of their diet, particularly during eel migration seasons.
Egrets
Similar to herons, egrets are stealthy hunters that prey on eels in shallow waters. The slender bodies and long necks of egrets like the great egret and little egret allow them to patiently stalk eels while remaining nearly invisible.
Once an eel is detected, the egret will swiftly snap it up in its pointed bill. Eels are an important source of nutrition for egrets, especially in wetland areas teeming with eel populations.
Kingfishers
Known for their bright plumage and fishing skills, kingfishers are agile birds that regularly feed on eels. Species like the belted kingfisher and common kingfisher watch for eel activity from low perches overhanging water.
When an eel swims near the surface, the kingfisher will plunge headfirst into the water to catch the eel in its vice-like beak. Kingfishers are able to swallow small to medium sized eels whole!
Cormorants
Cormorants are highly effective at hunting eels due to their excellent diving abilities. These waterbirds can pursue eels deep below the water’s surface. Species like the great cormorant use their hooked bill to snatch up eels from the depths.
Cormorants will often work together cooperatively to herd schools of eels into shallower areas where they are easier to catch. Eels that try to escape by burying in sediment are also sniffed out and consumed by probing cormorants.
Ospreys
Unique among raptors for their fish-catching skills, ospreys are powerful predators of eels. Using their keen eyesight, ospreys will circle high over bodies of water before plunging down to snatch up unsuspecting eels near the surface with their sharp talons.
The spiny ridges along eels make them more challenging for ospreys to handle compared to fish with scales. However, these birds have strong gripping feet and curved talons specially adapted for holding onto slick and wriggling prey like eels.
Marine Mammals That Feed on Eels
Seals
Seals are carnivorous marine mammals that belong to the family Phocidae. There are around 19 species of true seals, with populations distributed across the globe in subpolar, temperate, and tropical marine waters.
Seals have streamlined bodies and limbs that are modified into flippers, making them agile swimmers and divers. Their diet consists primarily of fish, squid, and crustaceans, but some species also prey on seabirds.
Many seal species are opportunistic predators that feed on eels. For example, harbor seals (Phoca vitulina) inhabiting estuaries and coastlines across the Northern Hemisphere consume substantial numbers of conger eels and moray eels.
Predation on eels tends to increase during the spring and summer months when juvenile eels migrate into coastal feeding grounds.[1] Grey seals (Halichoerus grypus) and Baltic ringed seals (Pusa hispida botnica) are also avid predators of eels, with eels sometimes comprising over 50% of their diet.[2]
Seals locate eels resting in crevices and burrows using their sensitive whiskers and ability to detect the electric fields generated by their prey. They are able to reach into tight spaces and grasp eels with their sharp teeth. Some species even wait along the shorelines to snatch up migrating eels.
The abundance of eels in a seal’s diet depends on availability and geographic location. But with their speed and dexterity, seals of all kinds find morays and other eel species to be a nutrient-rich food source.
Sea Lions
Sea lions are carnivorous marine mammals belonging to the family Otariidae. There are six extant species, found mainly in coastal waters of the Pacific Ocean. Sea lions are characterized by their ability to “walk” on land by rotating their hind flippers forward.
They have a varied diet consisting of fish, squid, octopus, and sometimes even seabirds.
A number of sea lion species opportunistically prey on eels. For example, Australian sea lions (Neophoca cinerea) are known to feed on conger eels in the Great Australian Bight.[3] Steller sea lions (Eumetopias jubatus) inhabiting the northern Pacific Ocean consume Pacific eels.
California sea lions (Zalophus californianus) have been observed predating on moray eels around oceanic islands.
Sea lions seem to especially target eels when they are migrating or spawning in large numbers close to shore. Their ability to plunge to depths of 300 meters gives them access to reef-dwelling eels. Sea lions grasp eels in their jaws and shake them vigorously to subdue them.
They seem to relish the abundant nutrients and fats contained in eels. So despite not being a primary prey item, eels contribute significantly to sustaining healthy sea lion populations across their range.
Otters
Otters are semiaquatic carnivorous mammals belonging to the family Mustelidae. There are 13 extant species, found in marine, brackish, and freshwater ecosystems across North America, South America, Europe, and Asia. Otters have long, muscular bodies and webbed feet suited for swimming.
Their diet consists mainly of fish, crustaceans, mollusks, and other aquatic invertebrates.
Some otter species prey on eels, especially in coastal wetlands where eels are abundant. For example, the Eurasian otter (Lutra lutra) is known to feed on conger eels around Europe.[4] Sea otters (Enhydra lutris) inhabiting kelp forests in the North Pacific Ocean eat moray and snake eels.
Male sea otters, which are larger, seem to target bigger eels compared to females.[5] The North American river otter (Lontra canadensis) includes eels in its varied diet across inland waterways.
Otters detect prey with their extremely sensitive whiskers and excellent underwater vision. They chase down and capture eels with their agile bodies and vice-like jaws. Otters consume all parts of eels, providing them with sustenance high in protein, omega-3 fatty acids, vitamins, and minerals.
So despite not being a primary food source, eels offer otters great nutritional benefits whenever they are seasonally abundant.
Other Eel Predators
In addition to birds and mammals, eels face threats from a variety of other predators. These include snakes, turtles, frogs, and even other eels.
Snakes
Many species of snakes feed on eels, especially younger eels. Some snakes that are known to eat eels include rat snakes, kingsnakes, and water snakes. Their slender bodies allow them to hunt effectively in aquatic areas.
According to Michigan State University, snakes account for up to 20% of eel deaths in some habitats.
Turtles
Aquatic turtles pose another danger to eels. Snapping turtles in particular are well known for their taste for eels and have powerful jaws that can crush an eel’s spine. Smaller turtles may target juvenile eels and eel eggs.
One study in a Florida spring system found that turtles were responsible for 55% of eel predation events.
Frogs
Large frog species will eat small eels and eel eggs when given the opportunity. Bullfrogs are an invasive species in many parts of the world where eels are found and are voracious predators of all types of small aquatic animals.
Other frogs less frequently eat eels but may still pose a localized threat.
Other Eels
In a remarkable display of cannibalism, eels sometimes feed on each other. Larger eel species especially may view smaller eels simply as prey. One study of European eels found that up to 65% had the remains of other eels in their stomachs.
So young eels must avoid their older cousins as well as other predators!
Where Eels Are Most Vulnerable to Predation
During migration
Eels are especially vulnerable to predation during their epic migrations. European and American eels migrate thousands of miles from their spawning grounds in the Sargasso Sea to inland freshwater habitats across Europe and North America.
This journey can take over a year to complete, during which the eels do not feed at all (what an amazing feat!). As the eels swim along coastlines and up rivers, they become easy targets for a wide variety of predatory fish, birds, and mammals.
Some key predators of migrating eels include:
- Marine mammals like seals, dolphins, and whales
- Large predatory fish like tuna, marlin, and shark
- Seabirds like gulls, terns, cormorants, and gannets
- Coastal raptors like ospreys and sea eagles
These swift predators are able to snatch up many vulnerable eels as they tire during migration. In fact, some predators like gannets and dolphins even wait along common eel migration routes to target these nutritious prey!
In shallow water
Eels living in shallow waters and wetlands are also very susceptible to predation. Here, eels of all life stages face threats from above and below.
Aerial predators like herons, egrets, bitterns, kingfishers, and some raptors plunge down from above to grab eels from shallow waters. On the hunt from below are larger fish species like pike, trout, bass, and catfish that patrol wetland edges.
Young eels in their “glass eel” stage are especially vulnerable in coastal wetlands, where predatory fish gorge on these tiny, transparent eels by the hundreds. Predation is so extreme that less than 10% of glass eels survive migration from the sea into freshwater habitats.
While spawning
Spawning eels also fall victim to mass predation. As mature eels aggregate to mate in the Sargasso Sea, they are set upon by ravenous predators. Humpback whales and porpoises arrive to feast on the spawning eels, as do large congregations of fish like bluefin tuna and shark.
In a kind of “perfect storm” situation, eel predation during spawning can be extreme due to:
- High eel densities concentrated in one area
- Eels being slow-moving and focused on reproduction, not evading predators
- Many different predators congregating at the eel spawning grounds
As a result, over 60% of spawning eels may be consumed by various predators annually. This intense predation pressure is one factor limiting eel populations today.
How Eels Try to Avoid Predation
Camouflage
Eels are masters of camouflage and blend in seamlessly with their environments. Their elongated bodies are colored olive, brown, green, grey or black, allowing them to disappear against rocks, aquatic plants and muddy bottoms (Source).
When threatened, eels can also alter their skin tone to better match their surroundings. Their lateral lines, which run the length of their bodies, help eels detect water currents and vibrations from approaching predators. This gives them advance notice to hide or flee the area.
Nocturnal Habits
Eels tend to be most active at night when their predators are sleeping. Their excellent senses allow them to hunt and navigate effectively even in total darkness. Eels have a thick, muscular body that moves in an undulating, serpentine motion, propelling them stealthily through the water without causing detectable ripples or splashes (Source).
By resting during the day and moving about at night, eels can largely avoid detection.
Hiding in Rocks and Crevices
During the day, eels seek refuge inside rocky crevices, under ledges, buried in sand or mud, or nestled within aquatic vegetation like seaweed. Their slim, flexible bodies allow them to squeeze into incredibly tight spaces where predators can’t reach.
Some eels even wriggle their way onshore and hide within wet burrows or under rocks until night falls and they can resume activity (Source).
Secreting Toxic Mucus
When threatened, some eels produce a toxic mucus coating that serves to deter predators. For instance, hagfish twist their bodies into knots and release mucus that turns the water into gelatinous goo when provoked.
Moray eels, congers and garden eels secrete skin mucus that contains toxic compounds harmful to predators (Source). This mucus makes eels distasteful and difficult for predators to grasp or consume, allowing time for the eel to escape.
Conclusion
As we’ve explored, eels face threats from a wide array of predators throughout their lives. Their diversity of habitats, from rivers to oceans, exposes them to fish, birds, mammals, reptiles, and amphibians looking for a nutritious meal.
However, eels have also evolved some clever defenses to help them survive and thrive despite the many animals that eat them.
Understanding these complex predator-prey dynamics provides fascinating insights into marine and freshwater ecosystems. Eels play a vital role both as hunter and hunted, and maintaining healthy eel populations benefits many other species as well.
Hopefully this article gave you a deeper appreciation of the eel’s place in nature and the survival challenges it faces.
