Shane's World Right Arrow Species Right Arrow The Oremon Catfish, Cephalosilurus fowleri • Article © Wolfgang Ros, uploaded October 06, 2008

Cephalosilurus fowleri
A 35cm specimen with typically rubiginous colouration
© W. Ros

Foreword
Among similar species, Cephalosilurus fowleri is regarded as the bad boy. As a species it comes with attributes like growing large, being extremely aggressive, voracious in appetite and also being very expensive to buy. But are these views well-founded?

Introduction
Four species have been described to the genus Cephalosilurus, all resident in South America. Three of these have been introduced into the aquarium trade up to now: C. apurensis, nigricaudus and fowleri. In terms of body shape they are only a little different from each other. Their trademark is the big head with little eyes and short barbels but with a mouht that is almost as wide as the head. They are sluggish animals which hardly move and only lie waiting for prey. C. fowleri is to be found exclusively in the Rio São Francisco of Brazil and there mainly in calmer flowing sections of the river.

Acquisition
This species is regarded as relativly rare, so acquisition can at least at times be difficult. Years ago, those few specimens exported almost without exception went to the Japanese market, known for its enthusiasm for big catfish and accepting of almost any price, the USA and Europe usually missed out. Recently however there were imports to Germany too. One will see the online stock lists of specialized dealers containing such a catfish, but some caution is required with the purchase. Because sometimes the cheaper C. apurensis and C. nigricaudus are offered as "100% true Fowleri". Since were are talking about a high price range, I would think every respectable dealer will understand if the interested party asks for a photo of the specimen offered before the purchase. Then if it should actually be the "true Fowleri" and the price is therefore correct, it is necessary to splash out. Sometimes one to two years can pass until the import of the next specimen. Depending on the number of imported animals the prices fluctuate strongly, in the past however have dropped considerably. In 2006/2007 a 15cm specimen only cost between 100 and 200€ in Germany; a mere 10cm bigger animal one could buy for approximately 200€ upward, the costs for potential delivery not included. The prices have strongly dropped since. So in April 2008 with a German dealer who imports direct, one could purchase an already 20 centimetres long animal at a bargain price of at least 50€. Also because each specimen occupied a tank by itself while for sale, they should probably find buyers soon.

Juvenile Cephalosilurus fowleri
Attractive juvenile colouration
© RVA

Juvenile Cephalosilurus fowleri
Another view of the young 14cm fish.
© RVA

Species identification
C. fowleri is the most attractive Cephalosilurus species. As in the case of all representatives of this genus there are specimens found with a bit of a different colouring. These deviations can not just be put down to differences between young and adult individuals since even equally aged animals sometimes are different in terms of colouring and patterning. Young specimens are brighter and often almost orange. The youth dress is primarily because of the contrasts arising by two more or less clearly defined dark body stripes, a slight grain with black-brown points and the dark unpaired fins make it very striking. As of about 20cm these contrasts increasingly lessen and the orange as a rule gives way to a rubiginous up to deep brown, party with dark spots that give a dress code better fitted to the natural surroundings. But even so animals with a yellowish basic colouring are not uncommon. Aside from the colouring C. fowleri is different from C. apurensis and C. nigricaudus by its slimmer shape and its flatter head. Moreover he almost completely lacks the spots on the belly underside.

Pre-requisites for keeping in the aquarium
In comparison with other predatory catfish which have long barbels and swim much more readily, an even bigger specimen of C. fowleri doesn't need proportionally much space. Tanks of about 600 litres are possible with respectively more volume if one wants to keep the catfish with other fish species. The depth of the aquarium should be at least 60 to 70 centimetres. An absolute necesicity for the well being of a fully-grown animal is an adequately big, natural or artificial, hiding-place. Bog wood or some form of terracotta vessel works well. Keeping C. fowleri without such a potential retreat, solely to ensure the animal is always on display, borders on torture. It is against their nature and such animals in an open area will try to dig themselves in the ground becuase, like his congeners, C. fowleri is quite averse to light. To make acclimatisation easier for them, the aquarium should only be moderately lit during the day or floating plant cover should provide darker zones in places. As aquarium gravel a mixture of gravel of finer granulation or sand is recommended. As to everything else, this catfish is tough and can thrive in a light current, a temperature range from 23 to 27°C and otherwise "normal" water parameters. In principle, they are robust in seeing off illnesses. If their fins, however, are damaged as can happen during transport or if kept with a badly chosen biting species or congener, then curing this damage will take a really long time. Therefore one can only seldom see really perfect animals.

Behaviour
Shortly after placing in the tank the keeper will find out how his C. fowleri retires to the hiding place created for it. A few days later the animal wil have waggled the bottom of its accommodation free of gravel. Even a medium sized specimen can release tremendous strength and is able to move, apparently without great effort, even a heavy shelter. Redecoration is acheived by pushing with its head and moving around with the tail fin to a place seemingly more pleasant for it. In this behaviour a similarity consists to the other Cephalosilurus-species which also live smugly in accommodation "fitted out" according to their wishes. If the previous hiding-place gets too small, then the keeper best put a bigger one in addition; C. fowleri will have accepted it gratefully at the latest after a few nights; thereupon the earlier abode can be removed.

Cephalosilurus fowleri
View on C. fowleri sleeping on the back in its cave
© W. Ros

Cephalosilurus fowleri
All Cephalosilurus stretch open their jaws after swallowing larger food items
© W. Ros

The keeper does not need to worry if his specimen needs a long time to acclimatise. Although a new arrival will normally hide almost all the time and, as Cephalosilurus go, will eat only moderately, they appear to otherwise be in good health. Not until after some months will it get a little more active. While C. apurensis, likely due to its greater appetite, will find its way out from its hiding-place even during the day; C. fowleri however still lives predominantly in seclusion. It takes an unusual resting position in its shelter, often laying on the back. However, the dozing catfish jumps to attention if food is given: it immediately comes out, snaps at the chunks which sink nearby and quickly retires again. As in the case of all Cephalosilurus, the keeper can observe that C. fowleri aids the digestion of larger food items by regular turns of its body, by rubbing its torso on cave wall and by stretching its mouth wide open.

Cephalosilurus fowleri
In a moment this specimen will leave its hiding-place to a stalk
© W. Ros

Cephalosilurus fowleri
A rare sight: C. fowleri completely outside of its hiding place
© W. Ros

If the acclimatisation process is completed, C. fowleri at the latest during the night, moves around the tank before it returns into its accommodation. Otherwise the animal can only usually be seen when it is hungry. Then it (particularly fully-grown specimens) will sometimes lean, the head held highest, against the side pane of the tank. But after feeding they then love to rest in their hiding places and to digest a meal in there.

As it moves, C. fowleri swims more jerkily and faster than its plump and portly congeners. Its agility is also of benefit to it while hunting. So C. fowleri is not only reliant like the other Cephalosilurus on waiting motionlessly and camoflagued so well that fish of suitable size fall into the attack zone which seems to be worthwhile for a sudden lunging bite.

In fact as an active hunter, it will additionly search between stones and wood with sporadic but astonishingly quick movements and when tracking down fleeing prey it can, in the blink of an eye, surge forward like a torpedo. As soon as the prey is grasped just once in the gigantic mouth it is held firmly tight with the help of the strong jaws and a multiplicity of smaller pointed teeth which are arranged in several rows. This hunting method I observed a few times with my specimen, after lights out, it hunted young Archocentrus nigrofasciatus, which, being still young and only a few centimetres long, had run for shelter under roots or between stones.

With the growth of these animals and primarily if kept in too small an aquaria, a little caution is demanded. Because then their aggressiveness maybe can increase. This aggression can even be aimed at the tank facilities like big stones or wood but also technical equipment. When keeping C. fowleri one therefore places heater, pump behind an adequately strong glass wall - best protection is found wholly outside the aquarium! This unpredictable behaviour is probably generally typical of the genus Cephalosilurus, however with C. fowleri fortunately much more weakly expressed.

Nutrition
Of course all species of the genus Cephalosilurus like taking living fish and particularly C. fowleri is said to eat only these in the aquarium at first. Apparently it can, however, get used just as quickly as C. apurensis and C. nigricaudus to substitute food. So it was with my specimen, which, already a few days after willingly starting to eat big earthworms and thawed smelt, then accepted prawns, mussels and fish fillet, too. It is particularly greedy when given trout pieces.

Cephalosilurus fowleri
First prey, a thick nightcrawler
© W. Ros

Cephalosilurus fowleri
Snapping at a given piece of fish fillet
© W. Ros

Like all Cephalosilurus-species C. fowleri also moves little and therefore does not burn much energy. Its big stomach is able to digest large portions however this should happen over several days like in nature. Best the keeper accustoms it to a firm feeding rhythm and provides food only every three to four days. This procedure, which is recommended for individual keeping, however can get greatly problematic when kept with other fish. Particularly in the summer months, if the temperature in the aquarium rises over the usual 25 ° Celsius, one must take into consideration the increased metabolism of the animals by an increase of food. Otherwise it can happen that they try to overpower equally sized co-inhabitants due to their increased appetite. In principle however, this danger with C. fowleri seems far less apparrent than with C. apurensis and C. nigricaudus which are much greedier.

It is easily recognizable when C. fowleri is hungry. Because then its accommodation does not function as resting place any more but now serves as a starting point for surprise attacks: The animal gets noticeably more restless and altogether more attentive; it is ready for a sudden attack.

Keeper interaction
For the predatory catfish enthusiast this species will soon be something special especially if they have raised their C. fowleri specimen from an early age. Interestingly this species uses its shelter also as an observation post with respect to the keeper. So my specimen immediately registers if I enter the room in which the tank is, because then it pokes its head of its hiding-place and approaches me bit by bit toward the front glass. Primarily bigger animals can be seen even with lights switched on and take food from the hand. It's a long road to acheiving this though, because C. fowleri remains rather reserved as opposed to the other Cephalosilurus-species. This is good however: with this species I do not run the risk of being bitten suddenly when giving “tender loving care”.

Cephalosilurus fowleri
Here the hungry predator has already become aware of me...
© W. Ros

Cephalosilurus fowleri
...and so partly leaves its dwelling
© W. Ros

Growth and final size
The growth of C. fowleri is comparatively and considerably slow. While C. apurensis for example, purchased as a young animal of 10 to 15 centimetres, if well kept is able to leap within only two years to 30 to 40 centimetres, for C. fowleri in the same time period are merely about 20 centimetres is realistic.

Its weaker growth suggests a smaller final size than at C. apurensis which encourages the keeper with the care of this species in the aquarium. The maximum length given at Fishbase for a C. fowleri male of 40.5 centimetres seems correct approximately. (cf. Fishbase website, at May 4th, 2008). If one compares the final lengths given there for the individual Cephalosilurus species, then the impression is given, though, that C. fowleri is the greatest of his genus. So for male specimen of C. apurensis a final length of barely 29 centimetres is given (cf. Fishbase website, at of May 4th, 2008). Actually that species might get the biggest with 60 to 75 centimetres. On various occasions in predatory fish forums discussed specimens of supposed C. fowleri that, on closer examination, turned out to be C. apurensis. Also the final size of over 70 centimetres ascribed to C. fowleri in some Japanese books could also be explained so.

Socialization
C. fowleri is said to attack and eat even bigger fish than itself. Though the maxim applies to all Cephalosilurus that the keeper should select solitary keeping, at least in principle, if they want to play completely safe and not to lose any co-inhabitants. On the other hand C. apurensis and C. nigricaudus in my experience are willing and able to swallow chunks of food much larger than their congener. With them, even when young, all co-inhabitants who are not bigger or not quick enough permanently live in the danger of being eaten. I can't speak against keeping C. fowleri with high back co-inhabitants. Especially if they are also robust enough like most cichlids and moreover the keeper follows the described feeding rhythm. Because otherwise this catfish, a predator by nature, will try to attack its flatmates in the night. This danger is particularly high if you did not consider a weak night illumination which ensures that other fish can make way for it on time at its occasional nightly wanderings.

Cephalosilurus fowleri
This species can safely be kept with bigger cichlids
© W. Ros

Cephalosilurus fowleri
In lurking position — big specimens tend to dominant behaviour, which however is weaker than its congeners
© W. Ros

When talking about aggressiveness, one should distinguish strictly between intra-species-aggression and the aggression towards other fish species. This is becuase in terms of intra-species, C. fowleri behaves extremely aggressively and territorially. At the latest at night even in a big tank the strongest animal will have harrassed its smaller comrade even after a short time so that its death can only be prevented by a moving it to another tank. The same is valid if one is trying to socialize different Cephalosilurus species. So after a short skirmish C. fowleri drove my C. apurensis back which I had added as a trial and which is not only a little bigger but seems also fundamentally stronger due to its bigger body mass. C. nigricaudus seems to surpass C. fowleri in aggressiveness, though.

Toward other big fish species however, C. fowleri acts altogether peacefully. While C. apurensis and C. nigricaudus know how to keep everybody at a distance if they approach their hiding-places, by threatening gestures and if required by biting, the territorial behaviour of C. fowleri is far less strongly pronounced. So my C. fowleri fends off smaller L-number plecos only when these want to tackle it too near to or stay even in its cave. On the other hand also this specimen has identified its area after some time in which it tolerates certain, predominantly mid to upper water co-inhabitants, bottom dwellers however know to keep at bay especially at night. Obviously its already got accustomed to some Heros efasciatus since they've living together a long time. I could never observe aggression between them. Of course the keeping of C. fowleri in adequately large tanks together with Potamotrygon species, with big Characins like the Red Pacu (Piaractus brachypomus) but also other predator catfish like Lophiosilurus alexandri which is also from the Rio São Francisco is conceivable.

The keeper should avoid keeping with territorial species though. Because only a few centimetres more in the body length can suddenly lead to a radical change in the nature of C. fowleri. Presumably this change is connected with the beginning of sexual maturity and a behaviour which thereafter is increasingly territorial. Primarily females then find increased self-confidence and rule to roost over all cohabitants. For moving purposes it is helpful in such a case if the keeper can resort to a further tank if necessary.

Differences between the sexes
Females might get a little bigger than the males. Especially when older differences in colouration become apparrent. Besides, as in the case of all Cephalosilurus species, the males are able to be identified by the form of the genital papilla which is longish and sharpened.

Summary
For the catfish enthusiast specialized in big predatory species C. fowleri surely due to its conspicuous colour, form and movement is worth keeping. Therefore whoever wants to put a “Ferrari” - and this nickname one aquarist has not given that wrongly to his specimen - into their big tank, I can only encourage this step; particularly since this species does not prove to be the such a bad lout either.

OAMLiterature

Notes
This article was originally published in July 2008 (p. 3-7) in the German Online Aquarium-magazine (OAM) published by Sebastian Karkus.
Mention must be made also of our debt to Takafumi Limura (Rayon Vert Aqua corporation Japan who gave us kind permission to publish three pictures in this article.


There is further information on this species on the Cat-eLog page.

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