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.
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