Colombian Shark Catfishes and other Ariidae

The Colombian Shark Catfish Sciades seemanni is the most widely traded brackish/marine catfish in the hobby. Contrary to the widely stated myth that catfish are somehow “allergic” to salt, there are actually a good number of catfish species adapted to brackish and saltwater habitats. But most of these salt-tolerant catfish are too large and too predatory to make good aquarium fish, with the Colombian Shark Catfish being a notable exception. It is fairly small, very hardy, and completely peaceful towards fish it doesn’t view as food.

But having said this, the Colombian Shark Catfish is not a fish for casual hobbyists. It isn’t a suitable addition to the average freshwater community tank, and while small by the standards of saltwater catfish, at up to 35 cm (14 inches) in length it requires a large aquarium with a robust filtration system. So despite being one of the most shark-like “sharks” in the hobby, it’s a fish to approach with caution.

Family Ariidae
Colombian Shark Catfish are members of a family known as the Ariidae. This group is extremely widespread, and found in shallow, warm waters around all the continents except Europe and Antarctica. The Hardhead Catfish (Ariopsis felis) for example is a very abundant species that can be found along the coast of the United States from the Gulf of Mexico as far north as Massachusetts. Anyone who has done saltwater fishing in this part of the United States will very likely encounter this notorious “bait stealer” sooner or later.

The juvenile Colombian Shark Catfish are in good health, with bright eyes and rounded bellies. © Bob Fenner

In Australia and to a lesser degree Asia, some of the Ariidae have become secondarily adapted to an exclusively freshwater lifestyle, but these are exceptional. Most of the Ariidae either live in the sea or brackish water habitats such as estuaries and mangrove forests.

While there certainly are strictly freshwater relatives of the Colombian Shark Catfish, they are virtually never traded, and you will never see them in the average tropical fish shop or pet store. If your retailer tells you that they have Colombian Shark Catfish in stock that don’t need brackish water, they’re either ignorant or lying.

Scientific names
The Colombian Shark Catfish is one of those fish that has had lots of scientific names over the years. It is currently referred to as Sciades seemanni, but older aquarium books may use the names Arius jordani, Arius seemanni, or Hexanematichthys seemanni instead.

Common names
Besides being called Colombian Shark Catfish, this catfish is commonly called the Silver-tip Shark and Black-fin Shark. The name recommended by Fishbase is Tete Sea Catfish, but that doesn’t seem to be used much in the trade. In the United States, this catfish is also occasionally called the Iridescent Shark Catfish, a name more commonly applied to the Asian freshwater catfish Pangasius hypophthalmus.

Description
Juvenile specimens are silvery-grey with white bellies and black pectoral, pelvic and anal fins edged with white. The dorsal, adipose and tail fins are plain grey. As they mature their colours become a little more muted, but adult Colombian Shark Catfish are extremely imposing fish. They are big, muscular fish and very shark-like in their appearance and swimming movements.

Adult Colombian Shark Catfish have slightly darker colours than the juveniles. © Bob Fenner

Distribution
As the name suggests, Colombian Shark Catfish can be found along the Pacific coastline of Colombia. But the total range of this species is much greater, extending from Mexico in the north to Peru in the south.

Ecology
Colombian Shark Catfish are not freshwater fish. They are very much estuarine and coastal saltwater fish that are rarely found great distances from the coastline. They will swim up rivers though, and can tolerate freshwater conditions for extended periods. But they cannot adapt permanently to freshwater conditions, and anyone buying Colombian Shark Catfish must appreciate that these fish need to be kept in a brackish or saltwater aquarium.

All of the Ariidae are opportunistic predators that consume small fish, crustaceans and a fair amount of carrion. Typical prey in the wild will include gobies, flounders, shrimps, small crabs and so on. They find their food a variety of ways; like other catfish, their whiskers help them detect chemical traces, but they are also sensitive to electric fields, so are able to find food hidden under the sand that would otherwise be undetectable. In this respect they are remarkably like sharks, the other group of fish noted for electro-sensitivity. The Ariidae are also unusual among catfish in being day-active, and rather than hiding in caves, prefer to swim about continuously.

Social behaviour
Colombian Shark Catfish are peaceful, if predatory, schooling fish. In terms of aquarium maintenance, they should be kept in groups of at least three specimens, and larger groups are even better. Singletons and pairs tend to be nervous and neurotic. Bullying behaviour is rare, and it is usually safe to mix specimens of very different sizes (though adding a tiny juvenile to a tank of big adults might be risky if the juvenile was bite-sized).

Reproduction
Colombian Shark Catfish are paternal mouthbrooders, but they haven’t yet been bred in captivity. A close relative, Ariopsis felis, has been bred in public aquaria, and it is assumed Colombian Shark Catfish breed in the same way.

In the case of Ariopsis felis, sexual dimorphism is limited to differences in the shape of the pelvic fins when the fish are sexually mature. On the females, the pelvic fins become larger and more fleshy. Spawning has not been observed, though it is has been hypothesised that the differently shaped pelvic fins may play a role of some sort, perhaps the female using her pectoral fins to hold clusters of eggs while the male fertilises them. Eventually the male takes into his mouth a clutch of up to 65 relatively large eggs and incubates them for about a month. He holds the fry for another 2-4 weeks while they use up the remains of the yolk sac. Once the fry are mobile and feeding, they male will mouthbrood them for a few days thereafter, should the fry be threatened, but soon the juveniles become completely independent.

Growth rate and adult size.
Colombian Shark Catfish grow rapidly. They will reach a length of about 20 cm (8 inches) within a year of purchase, and will be up to 30 cm (12 inches) long within two years. Maximum length in the wild is 35 cm (14 inches), but that is uncommon under aquarium conditions.

Colombian Shark Catfish are sociable and must be kept in groups. © Neale Monks

Sound production
The Ariidae are noted for being fish that produce sounds, and aquarists will sometimes here their Colombian Shark Catfish making audible clicking or drumming sounds.

It should be noted that sound production will often increase if the catfish feel threatened, and is seemingly used to bind the school together or to confuse predators. This can cause problems if the aggressive fish also uses sound. The author made the mistake of keeping Colombian Shark Catfish in a fish-only community alongside a Blue Triggerfish (Odonus niger) and the clicking sound of the catfish was clearly too much like the clicking noises triggerfish make when threatening one another. The end result was that both species became more and more stressed, with the catfish clicking in fear, and the triggerfish clicking in anger.

The Ariidae have unusual ear bones and appear to be more sensitive to low frequency sounds than most other fish, and together with their sound-producing abilities, it seems they have evolved some type of echolocation system similar to that used by dolphins. Since most of the Ariidae live in murky habitats, this is presumably a useful trick that allows them to navigate better than fish that rely solely on their eyesight or lateral line.

Given their sensitivity to low frequency sounds, it should be obvious that Colombian Shark Catfish are unlikely to be happy if maintained in noisy rooms. Sudden noises, like slamming doors, should be especially avoided.

Venom
All of the Ariidae are equipped with venomous pectoral and dorsal fin spines. Consequently they need to be handled with care. In general the risk to the aquarist is minimal, and they don’t use these spines as offensive weapons, even when frightened. But if you manhandle these catfish roughly, or try to grab a specimen trapped in a net, you may be in for an unpleasant surprise. The venom isn’t fatal, but it is extremely painful.

Incidentally, another trait the Colombian Shark Catfish shares with other Ariidae is that their saliva contains an anticoagulant.

Aquarium and filter requirements
To keep Colombian Shark Catfish you need to provide lots of swimming space and a strong water current.

Realistically, three adult specimens will need a tank at least 350 litres (90 US gallons) in size, and ideally a tank twice that size. This generous allowance of swimming space is essential because these fish are migratory, and even the biggest aquarium will feel cramped to them. When they are unhappy, Colombian Shark Catfish will sit in a corner of the tank, treading water. Often they will try to swim into the filter stream, seemingly looking to find a way out of the aquarium by swimming upstream.

As well as aquarium space, a strong filter is essential. Aim for a turnover of at least 8 times the volume of the aquarium per hour, and ideally more than 10 times. So for a tank 350 litres (90 US gallons) in size, the filter should be rated at not less than 2,800 litres per hour (720 US gallons per hour).

Water chemistry and salinity
Colombian Shark Catfish must be kept in hard, basic, saline water conditions. Juveniles will tolerate freshwater conditions very well for several months, but eventually they will become stressed and sickly. Unhappy Colombian Shark Catfish often tread water or show unusually dark colouration. Eventually they become subject to diseases like Finrot and Fungus.

Marine salt mix not than tonic or aquarium salt is required to make brackish water. There are numerous brands of marine salt mix, and for keeping brackish water fish, they’re all acceptable. For juveniles, a specific gravity of 1.003 to 1.005 will be fine, but specimens that are more than 10 cm (4 inches) long need to be kept in somewhat saltier conditions, around SG 1.010.
Adults can be kept in marine aquaria. Because they are predatory, tankmates will need to be of appropriate size, but otherwise Colombian Shark Catfish work well in fish-only and FOWLR marine community tanks.

Aquarium diet
Colombian Shark Catfish are adaptable, and will eat all sorts of things. A good quality catfish pellet can be used, alongside chopped seafood and white fish fillet, frozen insect larvae, krill and so on. They do feed mostly from the substrate though, so floating foods aren’t of much use.

Tankmates
Colombian Shark Catfish are predatory, and will eat tankmates small enough to fit into their mouths, but otherwise they are good community fish. Recommended tankmates include Giant Sailfin Mollies, Scats, Monos, Archerfish, Siamese Tigerfish, large Sleeper Gobies such as Dormitator maculatus, and brackish water Morays like Gymnothorax tile. If maintained in fully marine conditions, tankmates include Surgeonfish, Angelfish, Lionfish, Snappers, Groupers and large but not overly aggressive Damselfish.

Puffers and Triggerfish may be appropriate in some cases, but both of these types of fish tend to be nippy and aggressive, and this can cause problems when they are maintained alongside Colombian Shark Catfish.

Similar species
All the Ariidae seem to be very similar in terms of diet and social behaviour. This means that maintenance of all species is remarkably consistent apart from differences in size and, potentially, water chemistry in the case of the strictly freshwater Australian and Asian species.

The Spotted Shark Catfish (Arius maculatus) is a rarely imported species from Southeast Asia. While similar to the Colombian Shark Catfish in shape, it has grey rather than white fins and a distinctive black spot on the top of the adipose fish. Maximum length is around 50 cm, with lengths between 20 to 40 cm more common in the wild. Maintenance identical to the Colombian Shark Catfish.
The Blue Salmon Catfish or Berney’s Catfish (Neoarius graeffei) is a species from New Guinea and Australia that is occasionally imported. Despite its common name, it isn’t particularly blue except when small, the adults being more slaty-gray to brown. It is unusual in existing in distinct freshwater and marine populations. The freshwater populations live their entire lives in rivers, whereas the marine populations migrate between rivers and the sea. Maintenance of this species will therefore depend on whether the specimens on sale come from the resident freshwater population or the migratory saltwater population. The saltwater ones can be maintained just like Colombian Shark Catfish, whereas the freshwater ones will need to be kept in a freshwater aquarium with hard, basic water (pH 7.5-8, 15+ degrees dH). Maximum length is said to be 60 cm, though aquarium specimens are much smaller, typically around half that size.

Close
Colombian Shark Catfish are not difficult fish to keep alive, but they are difficult fish to keep well.

Further reading
Ariopsis felis. Smithsonian Marine Station at Fort Pierce, 2005
Arius maculatus. Fishbase, 2010
Neoarius berneyi. Fishbase, 2010
Neoarius graeffei. Fishbase, 2010
Sciades seemanni. Fishbase, 2010
Brackish-Water Fishes. Frank Schaefer, Aqualog, 2005
Brackish-Water Fishes. Neale Monks (editor), TFH, 2006

Ariid Catfishes on WWM

Colombian Shark Catfishes and other Ariidae

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