Ryan Photographic - Mormyridae - Elephantfishes


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Family Mormyridae

According to FishBase there are 198 species of the Mormyridae, commonly called elephantfish, in 18 genera.

I first learned about the mormyrids as a youngster. I spent way too much time poring over a Herbert Axelrod book on freshwater fishes of the world, returning time and again to the elephantfishes. The name elephantfish is derived from the elongate, downward pointing mouth. I was fascinated to learn that they could generate an electric field and use this to communicate with each other, avoid predators and find mates. Entirely restricted to Africa, they range in size from 5cm to 1.5m.

Elephantfish possess a similar brain to body weight ratio as humans - but before you consider them the Einsteins of the fish world, much of this brain mass is used in processing data from their electric field. Nonetheless they seem to have enough smarts left over to play. It is difficult enough to know what goes through the brain of another human, let alone a fish, so use of the term "play" may seem excessive. However, elephantfishes will manipulate things in their environment in a manner that does not seem to be in any way productive and some specimens will play "soccer" with aluminum foil balls. Having once watched a stingray repeatedly swim to the curved acrylic walkway in its aquarium and slide down again, apparently just for the heck of it, I need no convincing that some fish play.

Those elephantfish with down-pointing elongate snouts mostly feed on benthic invertebrates while the ones with a terminal (or slightly sub-terminal) mouth are mostly piscivores.

I was lucky enough to dive with so-called dolphinfish in Lake Malawi. Obviously quick learners, they arrived within seconds of us hitting the water. They hunted in a pack - probably 20 fish in total - but usually sub-divided into groups of 4 or 5. Together they pursued the cichlids which appeared mesmerized by our dive lights. But, despite this unfair advantage, they often missed their target. I estimated around a 30% success rate but this was not based on actual data - it is just a "guesstimate". Some of these fish must be fairly long-lived as one of them, "Scarface", has been around for at least 5 years.

I had problems with my underwater flashes during my two night dives in Lake Malawi so was somewhat distracted in trying to obtain good still photos. The end result is I totally failed to shoot good video. Fortunately good footage is available and if you promise to come back to my site again I will send you to Chisembe: Shadow Hunters of Lake Malawi filmed and narrated by Matt Arnegard. The Life on Earth, Freshwaters episode also contains excellent footage, filmed at Nkhata Bay where I took my still photos of Chisembe.

Unfortunately, the common English name for these extraordinary fish is Dolphinfish or Cornish Jack. There already is a marine fish called a Dolphinfish and Cornish Jack is just stupid. The fish is neither Cornish nor a Jack. I like one of the local names for it - Samwamowa - "those who can't drink beer" - an apparent reference to their relatively small mouth.

 

Mormyrops anguilloides Chisembe

Mormyrops anguilloides Chisembe (scarface) Nkhata Bay, Lake Malawi, Malawi

FISH 1956 Mormyrops anguilloides Chisembe (Scarface) Nkhata Bay, Lake Malawi, Malawi

Mormyrops anguilloides Chisembe, Nkhata Bay, Lakle Malawi - hunting group

FISH 1928 Mormyrops anguilloides Chisembe, Nkhata Bay, Lake Malawi - hunting group.

Mormyrops anguilloides Chisembe, Nkhata Bay, Lake Malawi  - hunting pack

FISH 1922 Mormyrops anguilloides Chisembe, Nkhata Bay, Lake Malawi - hunting pack.

Mormyrops anguilloides Chisembe, Nkhata Bay, Lake Malawi

FISH 1949 Mormyrops anguilloides Chisembe, Nkhata Bay, Lake Malawi.

Mormyrops anguilloides Nkhata Bay, Lake Malawi, Malawi

FISH 1993 Mormyrops anguilloides Nkhata Bay, Lake Malawi, Malawi.

 

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