Fish of the Lower Congo

Africa’s Congo River is the 10th longest river on Earth, but it is the world’s second greatest river by volume of water discharged.  In the final 300 kilometer (200 mile) span before the river empties into the Atlantic Ocean, the Congo is a deeply weird river…in that it is weirdly deep.  Portions of the Lower Congo have a depth of 220 meters (720 feet) which makes the Congo the world’s deepest river (chasmic freshwater locations are evidently a fascination here at Ferrebeekeeper). The bottom of the Lower Congo is not a serene place either, but is a dark world of treacherous currents, strange eddies, underwater waterfalls, and whirlpools.

Although these depths do not sound like the ideal place for, say, opening a sandwich shop, they are ideal for expediting the speciation of fish.  The Lower Congo has over 300 species of fish (and the number is growing as adventuresome ichthyologists study the native fish more closely…and as the river creates new varieties of fish).  The fast currents act like mountain ranges do on land, separating genetic pools of certain species so that they evolve in different directions.  This had led to some truly strange species such as the Gymnallabes nops (an air breathing catfish which is giving up on the scary river and crawling off into the moist leaves of the jungle), all sorts of exquisite elephant fish (Mormyridae) electrical fish which read the substrate with sensitive trunk like “noses”, upside-down polka-dotted squeaking catfish (which sounds like a rockabilly lyric), and, maybe best of all, Lamprologus lethops, a blind white cichlid of the chaotic depths which dies of decompression sickness when jerked up to the river’s surface.  When seen by Congolese fishermen, this cichlid is a bony blob of quivering pale agony gasping from a bony mouth.  This has led to the local folk calling it “Mondeli bureau” which means “white guy in an office” (an allusion to how they (correctly) imagine westerners look and feel in our miserable & pointless dayjobs).

This is exactly how I feel! Thanks for noticing, perceptive Congolese fisherfolk!

I wish I could tell you more about the wonders of the lower Congo, but research into this unique ecosystem has been surprisingly scant. I will keep my eyes open though.  I want to know more about those upside-down, polka-dotted, screaming catfish! I also want to write more about catfish of the Gymnallabes family.  Finally, I have a feeling there are even weirder fish at the very bottom of the river, we just don’t know about them yet.  We will keep our eyes on the Congo.  For the world’s second greatest river, we know a lot less than we should.

 

 

The Tripod Fish

Tripod Fish (Bathypterois grallator)

I promised more weird fish this year, and here is a fish which amply delivers on this promise.  This is a tripod fish (Bathypterois grallator), an eyeless wonder of the deep ocean plains.  The fish spends most of its time standing completely motionless on its elongated fins which reach up to a meter (three feet) off the seafloor.  It mostly copies the feeding habits of sessile invertebrates such as sea anemones and barnacles and feeds on tiny creatures which bump into its elongated (and highly sensitive) front and top fins.  It walks extremely slowly along the ocean bottom on these high fins with its mouth facing into the deep currents.

Despite its sedentary preferences and circumscribed lifestyle, the tripod fish has not given up its brain or its ability to swim.   If and when the fish decides to swim, its stilt like fins deflate and become flexible.  Scientists have not pinpointed the exact mechanism for this transformation, but erectile tissues are not unknown in the animal world. Speaking of which…

Mating is difficult in the abyssal zone (as any Tinder user could readily aver) so the tripod fish is a true hermaphrodite possessing both male and female reproductive organs.  If two tripod fish chance to meet, they mate together in all sorts of crazy troubling ways, however, if the fish never finds a partner it produces both sperm and eggs and mates with itself!