Background

The catfish family Clariidae comprises members of the genus Chanallabes, Clarias, Heterobranchus, Gymnallabes and Heteropneustes. All these fish have been well provided for, by nature, in the struggle for natural survival. Perhaps the best know genus within this family is that of Clarias so we turn our attention to these fish over the pages which follow.

Members of the genus Clarias, or flat-heads and walking catfish as they are commonly known, have the largest known natural range, which stretches through much of the African and Asian continents and into the Middle East (with Clarias gariepinus found in the Orontes river), of any catfish species. Little wonder then that since Belon erected the genus in 1655, by naming a catfish he caught in the Nile as Clarias nilotica, close to 200 (a number of which are now re-classified as synonym species) flat-heads have found themselves scientifically assigned within the Clarias genus.

As a result of such a wide ranging distribution Clarias have made their homes in a wide variety of habitats. Most species are at home in pure freshwater or brackish canals and other narrow waterways. Perhaps the strangest habitat is occupied by Clarias cavenicola (a fish whose future is very uncertain as a growing human population puts increasing pressure upon local water resources) which is endemic to the Algamas Cave of Namibia where survival comes from eating whatever carrion is washed into the cave through the action of draining surface waters.

As a teenager I clearly remember watching a wildlife documentary series which featured footage of a Clarias walking overland and remember how fascinated I was by this sight and it fuelled a growing interest in learning more not only about flat-heads but catfish in general. When Clarias walk they use a waving body movement, supplemented by auxiliary breathing organs (these have the appearance of sponge and are situated behind the gills in an extension to the gill chamber).and the usage of the pectoral fin spines as bracers, to move across short distances of land. Their gill covers remain tightly closed. When on land the small eyes, which are confined to an area within the body contour, will only allow a Clarias to see 2m into the distance and nature has found a way to protect these delicate organs from damage, caused through the effects of adverse bright light, by placing over them a thick layer of clear skin.

Much of this movement is dictated by seasonal weather patterns (taking advantage of flooded pineland glades has helped feral populations of Clarias batrachus move across areas of Florida’s famous Everglades) and the urge to reproduce. To risk the chance of predation (while in the safety of water courses this mainly happens to Clarias, who are spotted by large fish eating birds, taking the surface gulp of air needed to activate the auxiliary breathing organ) movement occurs in packs (as happens with members of the labyrinth genus Anabas – Climbing Perch) and these packs will make good use of any food resources they come across.

Out of interest it is not unknown for hungry or territorially disputing Clarias to kill members of their own kind. At the rear of their head these fish have a natural weak spot and thousands of years of evolution has given adult Clarias the instinct to inflict one bite to the exact spot that initially instantly paralyses and then, just as quickly, leads to the death of their chosen victim.

I guess fish farmers probably get their own back in the end as flat-heads have been a source of fish protein to human populations going back thousands of years. The earliest records of the human consumption of flat-heads come from Ancient Egypt. As happened in Europe with game the dead carcasses were left to begin the process of decay prior to consumption as the Egyptians believed that this actually improved the flavour of the protein rich flesh. Out of interest the Ancient Egyptians also consumed, when other fish species were scarce, the flesh of several Synodontis species.

Amazingly the first commercial farming of Clarias was carried out less than sixty years ago by Belgian workers living in the former Belgian Congo area of Africa. Today Clarias farming, in particular that of Clarias batrachus, is a very lucrative business with an end product that is marketed in live, fresh and frozen form. Much of the interest in consuming the flesh of Clarias batrachus (or Pantat, Masarai and Pla Duk Dan as this fish is also known) is believed to originate from the Indian state of Assam, whose people still have a strong and long held belief that this food has a special rejuvenating effect upon the human body.

In the hobby

For Nippyfish visitors who live outside of the U.K. the first thing to check is the legal situation regarding the keeping of any species of Clarias as their captive care is not only ‘banned’ in a number of countries with a tropical climate but extends into a number of non-tropical zones including the European mainland where, for example, it is against the law to keep such a fish in Germany.

The African flat-heads Clarias buettikoferi and Clarias gariepinus are occasionally available here in the U.K. Buettikoferi are grey in colour, originate from the western part of the continent and reach a maximum size of 19cm. Gariepinus, which can grow to 80cm, has a wide natural distribution and comes to us as both natural (sharptooth catfish) and albino (orange clarias) forms.

However the species most seen, as the result of the large scale commercial production, is the widespread, and large growing, Asian fish Clarias batrachus that outdoes gariepinus by coming to us not also in wild and albino forms but a lovely marble that is a ‘halfway house’ between wild and xanthic.

For more detailed information on the keeping of Clarias in aquaria and the fish species that will make suitable companions I refer visitors to my article mentioned at the beginning of this piece but briefly:-

  • 1. The minimum sized aquarium in which to house a single specimen, pair or trio of Clarias is 48x12x12″.
  • 2. Use small grained gravel as a substrate.
  • 3. The trio of marbled Clarias batrachus that lived in my care liked to sit upon patches of bare gravel and perch inside the fronds of large fern-like plastic plants. Although their aquarium contained a number of cave-like constructions none of these were ever occupied as permanent territories.
  • 4. Aim for a pH of 7 and a temperature of 26 C. Of much scientific debate is the fact that Clarias may need access to atmospheric air in order to maintain the function of their auxiliary breathing apparatus so always leave a gap of at least 1.25cm between the water surface and glass cover.
  • 5. Please note that whatever you weight the glass cover or condensation shield down with may not be enough to keep these fish within the aquarium.
  • 6. These fish are greedy feeders who take a wide variety of commercial aquarium fish foods.

My experiences

Prior to obtaining my trio of the marbled form I was informed that Clarias batrachus can be very territorial with each other, but I did not find this to be the case. The two larger ones, which turned out to be a true pair, had been with me for months, and had grown immensely, when the third fish found its way into my care as a ‘returnee’ to an aquatic retail outlet at York (my friend Elaine, who owns this outlet, was pleased to see this ‘free gift’ go home with me). Having read that larger Clarias will make a meal of smaller siblings the younger one was added with great caution and I made sure that I was around to see what happened, but need not have worried as they accepted its company straight away. Looking back I believe that this was more out of good luck than anything else?

Clarius batrachus

As a trio the three Clarias get along so well and have an almost uneasy truce. When one moves they all move, often in a very hyper-active manner, and when one rests they all, usually apart, rest. They dominate their aquarium without causing any problems to their companions. My concern is that they may reach a stage when they have to be moved to an aquarium of their own or that say the death of one of the trio will unbalance the situation, as I have heard of at least one aquarist who had the shock of finding a dead trio member upon their fish house floor before realising that the two remaining fish had literally ‘gone to war’, and when the larger fish dispatched its smaller relative to the ‘big aquarium in the sky’ it turned upon the other large fish species which shared its aquarium space.

Sue, my sister, asks me to mention that our trio of batrachus never appear to actually swim but literally fly round the aquarium such is their pattern of movement. Like several species of Botia they love to ‘play dead’ and thus are often to be found laying on their sides in a variety of positions. Although it worried me at first they love to sit on their tails, bolt upright in an almost dazed state staring at the surface.

These very greedy fish can consume, if given the chance, so much food at one sitting that they can become very ‘bloated’. When this happens I do not feed again for 48 hours and this allows for the excess food to be processed within their bodies. Their intelligence for food means that they recognise me as soon as my shape enters the fish house and to the surface they come for food and when this is not forthcoming show their disapproval by sulking upon the gravel.

Although their aquarium contains an excellent flow of air, following a feeding they will be found at the surface almost throwing their heads out of the water. This also worried me, although I wondered if it was to do with their auxiliary breathing apparatus, until I watched a television documentary on the Zambezi River in which several large Clariidae were seen doing exactly the same activity, with the narrator explaining that these fish round off a day of food foraging by hunting for insects at the water surface. Activity of a natural instinct carried on in aquaria?

Breeding

As the ‘Tropical World’ article covers this in much detail we will briefly look at the experiences of Ryedale member Mr. Paul Campion who enjoyed both the thrill and despair of spawning a pair of albino batrachus, on several occasions, during the late 2000s. Paul found that it took a two thirds change of water, with water that had been stood for a day added as a replacement, in order to get his pair of batrachus to spawn.

Pre-spawning was always indicated by the pair’s increased appetite and the nudging of each other’s genital regions. Eggs were then released during a wrapping movement. The aquarist whose batrachus were the parents of Paul’s pair told him that, with a lack of suitable nest building sites, these fish had dug a primitive nest into the gravel, but no nest was ever constructed a generation on as the female just scattered eggs all over the substrate. The male then fertilised these eggs, but although a large number had been shed each time not one egg would ever prove to be fertile.

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