Transcript:

Today on Animal Fact Files we’re discussing the wels catfish. Also known simply as wels, these fish are some of the largest living in their range. Wels catfish are native to Europe and Asia but they've been introduced in other areas as indicated in orange on this map. In size, these fish are known to reach more than eight feet (2.4m) in length and over 300 pounds (136kg) in weight, however, these humongous individuals are few and far between. It takes excellent habitat conditions for a wels catfish to reach this size. They obtain about half these numbers on average which is still impressive! These fish live in slow moving waterways like lakes, rivers, and sometimes near coastlines where they can tolerate brackish water. They like muddy or sandy bottom areas with lots of vegetation and debris amongst which they can hide.

Outside of the breeding season, these fish are solitary. When they do meet up to mate, the male digs out a nest into which the female lays her eggs. They can be told apart by a flap of skin under their vent. The vent in a fish is the opening through which waste and reproductive material pass. In female wels catfish the flap of skin just past the vent is wide and short, in males it's long and pointed. Thousands of eggs are laid in the male’s nest, and he'll spend the next days to over a week protecting his brood. The eggs develop more quickly in warmer temperatures. The babies remain in the nest for a few days after hatching before dispersing. Male wels catfish grow and mature faster than females, reaching reproductive maturity between two and three years of age. Females take three to four years before they're ready to mate. The expected lifespan of these fish ranges from 20 to 30 years though the oldest known individual was 80!

Wels catfish are nocturnal, meaning they're most active at night. They spend most of their time at the bottom of the water column and eat just about anything they can fit in their giant mouths. Like grouper, wels catfish use suction to capture their prey. The larger the fish, the bigger the meal. Young wels catfish eat small invertebrates like insects and crayfish, while bigger individuals eat other fish as well as rodents and even birds! They're known to throw themselves out of the water to catch birds resting along the water's edge. Wels catfish are eel shaped with long, flattened tails and a strong upper body. They can swim backwards if needed! They have tiny eyes that aren't very useful for catching prey. Instead they use other senses to pick up on the presence of prey. They have two long barbels that protrude from above their mouth and two pairs of shorter barbels along their lower jaw. Their dorsal fin is tiny!

Predators of the wels catfish include otters, cormorants, and other fish like pike. They're also known to eat each other! Of course, the larger they get the less the chance they end up on the menu. They're also captured by humans who fish them for sport and for food. Habitat destruction also threatens the wels catfish, though they are quite tolerant and are considered a pest in areas they've been introduced due to their destruction of native species. Wels catfish have no scales and are described as slimy. Their eggs are also mucousy and adhered to objects such as tree roots while they develop. Their mouths are huge and full of small, backward facing teeth designed to trap prey. Supposedly, large wels catfish attack humans, though these claims are most often made by anglers after releasing a wels catfish after a catch. Still, it may make you think twice about entering a river for a quick soak!

For more facts on the wels catfish, 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! Thank you to these viewers for today’s request! And thank you for watching Animal Fact Files!