Ugly fish: Siluris glanis 'freshwater killer'

science | Dec 08, 2012 | By Martin Barillas


Researchers in Europe have captured on video something that this writer concluded long ago: nature is not only surprising and miraculous, but also sometimes very nasty. It was on the River Tarn in southwestern France where scientists studied the European catfish known as the Wels catfish, and by its scientific name of Siluris glanis. It was there that they witnessed what some are calling evidence of adaptive behavior among fish that can reach as much as 320 pounds in weight and over 9 feet in length. There are legends that in the 1800s, specimens of over 13 feet in length were caught in Europe. But I digress.
What scientists recorded on video and reported in the online Plos One scientific journal was that these catfish have beached themselves on river banks to hunt live pigeons. Yes, you read that right. 
The researchers saw specimens of S. glanis lunging out of the water to grab a pigeon with their gaping mouths and swallow their hapless and fluttering prey. In doing so, they manage to temporarily strand themselves on land for a few seconds. Dragging the pigeons back into the water, the fish feast on fowl. 
Dolphins and orcas, the latter of which are also known as ‘killer whales,’ are also known to engage in the same behavior. But they are much smarter and, well, cuter somehow. Orcas throw themselves up on to the antipodean beaches of South America to devour seals and penguins, giving yet another meaning to a surf-and-turf dinner.  Researcher Julien Cucherousset from Paul Sabatier University in Toulouse has taken to describing the catfish in question as "freshwater killer whales."
"Among a total of 45 beaching behaviors observed and filmed, 28% were successful in bird capture.  … Since this extreme behavior has not been reported in the native range of the species, our results suggest that some individuals in introduced predator populations may adapt their behavior to forage on novel prey in new environments, leading to behavioral and trophic specialization to actively cross the water-land interface."
The mouth of an S. glanis contains ranks of numerous small teeth, two long barbels or whiskers on the upper jaw and four shorter barbels on the lower jaw. It has a long anal fin that extends to the caudal fin, and a small sharp dorsal fin is positioned relatively far forward. It actually uses its sharp pectoral fins like stubby arms to capture prey. With these fins, it creates an eddy to disorient its victims, which it then simply engulfs in its enormous maws. It has very slippery  eel-like green-brown skin. Its belly is a deathly pale yellow or white, while the rest of the body color varies according to environment. Which is to say that it normally looks like mud. In clear water, it will appear black in coloration. Weight and length are not correlated linearly, and also depend on the season.
Each female can produce up to 15,000 per pound of body weight. The male guards the nest until the brood hatches, which, depending on water temperature, can take from three to ten days. If the water level decreases too much or too fast the male has been observed to splash the eggs with its mighty tail in order to keep them wet, according to some reports.
Siluris glanis is the third largest freshwater fish in the world and the second largest in European waters, having been introduced to Western Europe from the East. Large specimens have been caught in various river systems of Europe, including the Rhone, Ebro, Rhine, Dnieper, and Danube. 
Of the fish in Europe, scientists believe that it is among the least threatened piscine species. And with good reason: with that type of adaptive aggression, people ought to be concerned about S. glanis on their next riverside picnic. The freshwater killer awaits.
Scientific classification:
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Siluriformes
Family: Siluridae
Genus: Silurus
Species: S. glanis
Binomial name
Silurus glanis
Linnaeus, 1758



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Spero News editor Martin Barillas is a former US diplomat, who also worked as a democracy advocate and election observer in Latin America. His first novel 'Shaken Earth', is available at Amazon.

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