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Today on Animal Fact Files we’re discussing freshwater eels. As their name implies, these eels spend most of their lives in freshwater, though there's more to the story. It should be noted that even though these are called freshwater eels, they're not the only eels that live in freshwater. More specifically, they're "true" eels, meaning they're classified in the same order as other "true" eels. Other freshwater eels, such as the electric eels for example, are not considered "true" eels, so they aren't part of the group. Electric eels are actually knifefish and more closely related to catfish. They just got their name from their eel-like body!

Freshwater eels have a long body, though females can greatly outsize the males. Most freshwater eels average about a foot and a half (46cm) in length, though the longest species can reach five feet (150cm) long! There are just over a dozen classified freshwater feel species. These fish are nocturnal. They spend the day hiding in vegetation, crevices in rocks, or buried in the substrate. They live in lakes, rivers, streams, ponds, and more, but they're also found in oceans almost all over the world! Freshwater eels are catadromous fish. What this means is they are born in saltwater, live their adult lives in freshwater, and then return to saltwater to reproduce. They're the opposite of some trout! In fact, like salmon, freshwater eels use their sense of smell to find their way to fresh or saltwater depending on which way they're traveling.

Freshwater eels start their lives as eggs. A female releases hundreds of thousands to millions of buoyant eggs in deep water marine habitats. These are fertilized externally by the males. The eggs hatch into planktonic, leaf-shaped larvae that ride on oceanic currents for one to three years before they are pushed to warm coastal waters. Here, they develop into transparent 'glass eels' that resemble their parents. After about a year, they develop into dark colored, bottom living 'elvers'. At this point, they travel into freshwater and further develop into adult eels. They'll remain here for up to twenty years before returning to the sea. Females generally travel further inland and take longer to mature than males. When they return, it's a one way trip because, like an octopus, a freshwater eel dies after mating.

Unlike other eels, freshwater eels have scales. These are oval shaped and embedded in the eels' skin. They also only appear in adults. Freshwater eels have a dorsal fin that runs along the back and connects to the caudal, or tail, fin. Their jaws have many small, sharp teeth which are useful for catching prey like worms, crustaceans, insects, snails, crayfish, clams, fish, and more! In turn, freshwater eels have to watch out for predators like cormorants, herons, and predatory fish. If necessary, they can live outside of water for hours as they're able to breathe air.

For more facts on freshwater eels, check out the links below. Give a thumbs up if you learned something new today. Thank you to our Patrons SpikeSpiegel93, Dad, and everyone else for their support of this channel! And thank you for watching Animal Fact Files!