Better than its reputation, a look at Cephalosilurus fowleri

Wolfgang Ros

http://wolfgang-ros.de.tt

mong the representatives of this genus, Cephalosilurus fowleri is regarded as having the worst reputation. The information which pertains to this species so far can be summarized in this way: Grows very big, extremely aggressive, voracious and is also a very expensive acquisition, but is this view well founded?

 

Four species have been described to the genus Cephalosilurus resident in South America. Three of them have been introduced for keeping in the aquarium, C. apurensis, C. nigricaudus and C. fowleri. From their form they are only little differences from each other.

 

Their trademark is the big head with the little eyes and short barbles but with an almost head wide mouth. 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 the more calm flowing river sections.

 

C. fowleri, 35 cm in length with its typically rubiginous colouring (© W. Ros).

 

 

 

 

 

 

Acquisition:
This species is regarded to be relatively rare, so in this respect its identification at times can be difficult. Some years ago the few captured specimens almost always without exception have been transferred to Japan whose residents have a great enthusiasm with big catfish and accept them at almost any price. The USA and Europe markets with imports were usually excluded, lately however there has been imports into Germany. One would be bound to sight the on-line stock lists of specialized dealers to acquire such a catfish, but some caution is required with the purchase, because sometimes the cheaper C. apurensis and C nigricaudus are offered "for 100 per cent" the"true Fowleri". Since it is here in the elevated price range, every respectable dealer will understand if the interested party asks for the sending of a photo of the offered specimen before the purchase. If it should actually be the "true Fowleri" and the price is correct, it is necessary to be quick with the purchase as 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 it has dropped considerably. In 2006/2007 a 15 centimetres large specimen only costs between 100 and 200 euros in Germany; specimens at ten centimetres could be bought for approximately 200 euros upward, the costs for a potential delivery not included. The prices have dropped further so that in April 2008 with a German dealer who imports himself, one could purchase a 20 centimetres long animal at a bargain price of at last 50 euros. Probably also because each specimen occupied a tank on its own and therefore could soon find buyers.

 

Species identification:
C. fowleri is the most attractive Cephalosilurus species. As in the case of all representatives of this genus there are also specimens of a bit different colouring. These deviations alone can not be put down to the youth / adulthood since even older animals can sometimes be different in colouring and patterning.

 

In terms of colour these three are attractive young specimens of 14 cm in length (© ).

Young specimens are more brightly coloured and often almost orange. The juvenile colouration is primarily because of the contrasts arising by two more or less clear dark body stripes, a slight grain with black-brown spots and the dark tail, anal, adipose and dorsal fins are very striking. At about 20 centimetres these contrasts fade away increasingly and the orange as a rule gives way to a rubiginous, up to deep brown, with dark spots with the colour dress fitting better on the natural surroundings. But even so animals with a yellowish basic colouring are not rare. Aside from the colouring C. fowleri is different from C. apurensis and C. nigricaudus by its slimmer shape and its flat head. Moreover it almost completely lacks the spots on the underside of the belly.

Preconditions for keeping in the aquarium:
In comparison with other predatory catfish which have long barbles and are swimming constantly even bigger specimen of C. fowleri don’t need much space. Tanks of about 600 litres are possible respectively with 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. A fully-grown animal for his well being should have natural or artificial hiding places to be created, bog pine or a vessel of terracotta offers itself as such a hideout. Keeping C. fowleri without such a retreat only makes it look to the casual observer as if the catfish is possibly in torture. Against their nature such animals can even, on an open area, try to dig themselves into the ground. Like his genus comrades C. fowleri is quite averse to light. To make the acclimatisation easier for him, the aquarium should only be moderately lit during the day or a floating plant cover should provide darker zones in places. As aquarium gravel, a mixture of gravel of finer granulation or sand is recommended. For the rest this catfish is tough and can be kept well at a light current, a temperature span of between 23 to 27° Celsius and otherwise normal water parameters. It seems to be robust in principle when it comes to diseases, however if his fins are damaged, as it can happen with transportation or wrong keeping, due to biting with species or genus comrades, then the cure phase lasts for a quite considerable time, therefore one can see only seldom, really perfect animals.

Behaviour:
Shortly after placing in the tank the keeper will find out how his C. fowleri will retire to the hiding-place created for it. A Few days later the animal has waggled the bottom of its accommodation free of gravel.

Already a medium-sized specimen can have tremendous strength and is able to move, apparently without great effort, even a heavy shelter by pressure with the head and moving around with the tail fin to a place seeming more pleasant for it. In this behaviour a similarity consists to the other Cephalosilurus species which also live with pleasure in an accommodation and "fit it out" according to their wishes.

If the previous hiding place has got too small, then the keeper puts a bigger one in addition to the original one. When C. fowleri has gratefully accepted it after some nights, thereupon the earlier shelter can be removed.

View of C. fowleri sleeping on its back in cave (© W. Ros).

The keeper does not need to worry if his specimen needs much time for the acclimatisation, because C. fowleri normally at first will almost at all times hides itself and eats, for a Cephalosilurus species, only moderately even if it enjoys itself in apparently good health. Not until after some months does it get a little more active. While C. apurensis, due to its greater appetite, already has at times finds its way out from its hiding place even during the day, C. fowleri however still lives predominantly in seclusion, often laying on its back and taking an unusual resting position in its shelter, however this catfish becomes wide awake 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 species the keeper can observe in that C. fowleri helps its digestion of larger food pieces by regular turns of its body, by rubbing of the epigastrium (the region lying on or over the stomach, just below the sternum) at the feeding place, and by tearing its mouth wide open.

If the acclimatisation process is completed, C. fowleri at the latest, at nightfall, moves around through the tank before it returns into its accommodation. Besides that the animal can be seen as soon as it is hungry, then particularly fully-grown specimens can sometimes lean, the head held high, against the side glass of the tank.

But after feeding they also love to rest in their hiding-places and to digest the food there, also then if it is only behind a big root.

Like its genus comrades C. fowleri, after swallowing larger chunks, tears its mouth wide open a few times (© W. Ros).

C. fowleri makes its swimming movements more jerkily and faster than its plump, far more portly appearing genus comrades. Its agility is of benefit to it also at hunting time.

So C. fowleri is not only reliant like the other Cephalosilurus species on waiting motionlessly and disguised very well that fish of corresponding size fall below the attack circle, which seems to be worthwhile for a sudden bite.

In a moment this specimen will leave its hiding place to stalk (© W. Ros).

In fact as an active hunter in addition it can search the ground between stones and woods with, from time to time, astonishingly quick movements and when tracking down scared prey it can push forward like a torpedo as quick as a flash. As soon as the prey is grasped once with the gigantic mouth, it is hold firmly tight with the help of the strong jaw and a multiplicity of smaller pointed teeth, which are arranged in several rows.

This hunting method I could observe a few times of my specimen, and with turning out the aquarium light it hunted a few two or three centimetres long young Archocentrus nigrofasciatus which had run for shelter under roots and between stones

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

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

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

Like all Cephalosilurus species C. fowleri also moves little and therefore does not burn up much energy. Its big stomach is able to digest large portions however this should happen over several days like in nature. It is best that the keeper accustoms it to a firm feeding rhythm and gives only food every three to four days. This procedure, which is recommended for individual keeping, however can get problematic with other fish socialized specimens. 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 equal long co-inhabitants due to their increased appetite. In principle however, this danger with C. fowleri seems to be given far less than C. apurensis and C. nigricaudus who are much more greedy.

C. fowleri with its first prey, a thick nightcrawler (© W. Ros).

It is easily recognizable when C. fowleri is hungry, because then its accommodation does not have the function as a rest room any more but now serves as a starting point for surprise attacks. The animal gets noticeably more restless and altogether more attentive, it is then ready for a sudden attack.

Relations to the keeper:
For the predator catfish enthusiast this species will be something special, especially if he has raised his 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 it if I enter the room in which the tank is, because then it then juts its head out of its hiding place and approaches me bit by bit towards the front of the tank. Primarily bigger animals can be seen even if lights are switched on and can take the food out of the hand. Until then it is a long journey though, because C. fowleri remains rather reserved as opposed to the other Cephalosilurus species. It is good that they are different though as I do not run the risk of being bitten suddenly when giving “tender loving care”.

Growth and final size:
The growth of C. fowleri is comparatively slow compared with C. apurensis for example. When purchased as a young animal of 10 to 15 centimetres C. apurensis is able to take a great leap, if it is in a sufficient place and with good feeding, and within only two years it can grow to 30 to 40 centimetres. For C. fowleri in that same time period, 20 centimetres is more realistic.

Its slower growth suggests a smaller final size than C. apurensis which obliges 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 should be approximately correct . ( Fishbase website, status of May 4th, 2008). If one compares the final lengths having been noted for the individual Cephalosilurus species then the impression is given, though, as if C. fowleri is the largest of the genus. So for male specimens of C. apurensis a final length of barely 29 centimetres is given (Fishbase website, status of May 4th, 2008). Actually this species might get the biggest with 60 to 75 centimetres. On various occasions in predatory fish forums specimens are showed of supposedly, C. fowleri, but on on closer examination turn out to be C. apurensis. Also the final size of over 70 centimetres ascribed to C. fowleri in some Japanese books could be explained also.

Socialization:
C. fowleri is said to attack and eat up even bigger fish. Though the maxim applies to all Cephalosilurus species that the keeper should decide, for single keeping in principle, if he wants to play completely safe to lose no 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 genus comrade. With them even in their youth all co-inhabitants who are not bigger or not quick enough permanently live in the danger of being eaten. With C. fowleri if socialized you should be all right with high backed 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, which is living predatorily by nature will try to attack its flatmates in the night. This danger is particularly high if you did not think to give a weak night illumination, which ensures that other fish can make way for it on time on its occasional nightly wanderings.

This species can safely be socialized with bigger cichlids (© W. Ros).

With this aggressiveness it is important to distinguish strictly between the intra-species aggression and the aggression towards other fish species. With intra-species aggression C. fowleri behaves extremely aggressively and territorially. At the latest at night, even in a big tank, the strongest animal will have pressed its smaller comrade after a short time so that its death can only be prevented by moving to another tank.

The same is valid if one is trying to socialize different Cephalosilurus species. 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.

C. fowleri in lurking position – big specimens tend to dominant behaviour, which however is weaker than with C. apurensis and C. nigricaudus (© W. Ros).

Towards other big fish species C. fowleri altogether acts peacefully, while C. apurensis and C. nigricaudus know how to keep everybody at a distance who approach their hiding places, by threatening gestures and if required, by biting. The territorial behaviour of C. fowleri is far less strongly pronounced. My C. fowleri fends off smaller L-catfish only when they want to tackle it, are too near or stay even in its cave. On the other hand this specimen also has marked its area after some time in which it tolerates certain, pre-dominantly staying in the upper half, co-inhabitants. Bottom dwellers however know to keep at bay primarily at night. Obviously it has already got accustomed to some Heros efasciatus since they have been living together along with it, I could never observe aggressions towards them. Of course the keeping of C. fowleri in adequate big tanks together with Potamotrygon species, with big Characins like the Red Pacu (Piaractus brachypomus) and also other predator catfish like Lophiosilurus alexandri which is also living in the Rio São Francisco, is conceivable.

The keeper should avoid socialization with territory forming 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 therefore is becoming more territorial. Primarily females then shall offer increased self-confidence and play the rulers over all co-habitants. 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 also consist in the coloring. Besides as in the case of all Cephalosilurus species, the males can be identified at the form of the genital papilla, which is longish and sharp.

Summary:
For the catfish enthusiast specialising in big predatory species, C. fowleri, due to its conspicuous colour, form and movement is worth keeping. Therefore who wants to put a “Ferrari”, as this nickname one aquarist has not given quite wrongly to his specimen, into a big tank, I can only encourage him to carry out this step, particularly since this species does not prove to be quite the bad lout either.

Literature:
Werner, A. (2005): Neu importiert - Cephalosilurus fowleri, Datz 58 (11): 29.
Ros, C. und W. Ros (2007): Cephalosilurus apurensis - Ein gefräßiger Lauerräuber, aber nicht ohne Charme, Datz 60 (5): 38-42.
Ros, W. (2008): Cephalosilurus nigricaudus und seine Abgrenzung zu Cephalosilurus apurensis, AF 40 (1), Nr. 199: 34-36.

This article came out 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.