Sharks

We fishkeepers call them “sharks”. But we are not trying to fool anybody. These popular tropical freshwater fish can only be likened to the true marine sharks in the most oblique fashion. True, they have a streamlined form, some an underslung mouth, others a “triangular-ish” dorsal fin. That, with sufficient imagination, could perhaps justify this loose naming of those freshwater Cyprinids marketed as “sharks”. It certainly has all to do with marketing, and nothing at all with scientific classification! Labeos, Eplazeorhynchus, Balantocheilus, Leptobarbus, are the genera where these freshwater “sharks” are mostly found.

There are a few exceptions but in general the quarrelsome nature many of these species share is another factor which could build some further credibility into their “shark” image. The Red tailed black shark and Ruby shark, for example, are notorious for battling with each other, but some members of both species are equally capable of targeting unrelated members of their community and persistently harass these unfortunates to a premature end. A black shark is most likely to grow into a solitary monster, unwilling to tolerate any potentially compatible alien companions or even others of its own kind to share territory.

The Labeo and Epalzeorhynchus species are often promoted as algae eaters, and it is true that some species are seen to browse over the leaves, decor rocks, and glass. But in general they are hardly dedicated vegetarians. Juvenile Siamese flying foxes Eplazeorhynchus siamensis, however, might fairly be commended for their algae consumption. But they are not marketed as “sharks”, so are not being considered here. But for the majority their requirement is for a varied diet to include a broad spectrum of food types and ingredients, with algae as an incidental item. Regular modest feeds are eminently preferable to infrequent over-generous “blow-outs”. Maintaining a nicely filled out body shape with regular moderate offerings of interesting foods goes a long way towards keeping the peace.

Hungry freshwater sharks, or those deprived of an interesting and nutritious diet, are likely to be troublesome marauders at one extreme, or lethargic, dispirited fish which head for an early demise at the other extreme. Sometimes bought as “scavengers”, the bottom feeding sharks are badly misjudged on this basis. Their feeding requirements need to be particularly well thought out. A variety of dried convenience foods may form the main menu, but be sure to give some fresh, live, or frozen “meaty” foods regularly too.

The ideal aquarium should be spacious, the size being determined by the species to be kept. A fully grown Black shark (Morulius chrysophekadion) will need more space than an adult Red tailed black shark (Labeo/Epalzeorhynchus bicolor), for example. (Some species previously described as Labeos have in recent times been reclassified in the genus Epalzeorhynchus, but in most books they will be found referenced under Labeo). And while the Black shark will probably end up in solitary confinement the Red tail will more usually be part of some kind of mixed collection. Silver, or Bala, sharks (Balantocheilus melanopterus) are almost invariably totally peaceful in spite of their large adult size. But they are also often hyper-active fish, needing water with a high oxygen content and S-P-A-C-E. The spaciousness of the aquarium should also permit the construction of rocky niches to provide a sense of security for the more reclusive “shark” occupants. In addition plant thickets will serve a similar purpose. The lighting needs to be sufficiently strong for comfortable viewing and to serve the needs of the plants, but not more. The fish will prefer more subdued lighting, which the decor and plants might well combine to provide. By choosing the plants with care it is possible to have suitably sturdy species which in turn do not demand high light levels. Broad leaves are preferable to delicate fine ones. Species of Cryptocorynes, Anubias, and to a lesser extent Echinodorus “Sword” plants, are particularly valuable in this respect.

The underslung mouth of those species the in the genera Epalzeorhynchus and Labeo indicates a “grubbing” type of fish. But they are not rightly described as bottom feeders, as they will actively browse from leaf and decor surfaces well off the bottom. The stumpy barbels, however, are particularly useful when they are raking across a soft substrate. But aquarium substrates are not usually anything other than coarse, and although these species will grub between the gravel grains they are loath to really delve in with enthusiasm. Silver Sharks, Apollo sharks (Luciosoma setigerum), Festive apollo sharks (Labiobarbus festiva), Red finned cigar sharks (Leptobarbus hoeveni), and “Tiger” sharks (species of the genus Pangassius) do not have similar mouths to those species mentioned above. They possess the more frequently seen tip-of-the-snout siting, or just slightly underslung lower jaws. Equipped in this way they are more likely to take floating or sinking food, showing less of a preference to routing through the substrate, or winkling out titbits from rockwork.

It is the Silver shark, Red tailed black shark, and Ruby shark, which far and away take the largest part of the market when we consider the range of freshwater species embraced by the banner name of “shark”. All three species are most likely going to be found in “community aquariums” which provide the bulk of the aquarium fish market. The Silver shark was formerly fished from its native waters in Thailand and Malaysia to supply the world market. But collections soon depleted wild stocks to crisis levels and supplies were erratic and highly priced at best, non-existent for long periods at worst. Today’s supplies are coming from farm produced fish, assisted in their breeding efforts by hormone treatment. The main benefit of this domestication is the conservation of the wild stocks, of course, but additionally the hobbyist enjoys a less stress-prone fish which travels better and takes to life in the glass box far better than its wild ancestors ever did. On the down side the writer has noticed a loss of the former strong yellow colour which the black edged tail used to sport to such great effect.

The Red tailed black shark is another species which used to be available to the hobby on a strictly seasonal basis, when wild stocks were the only source of supply. The first fish of the season were usually minute babies which were far too small to stand the rigours of collection, holding, and export. On arrival they were often emaciated through lack of food essential to such baby creatures. Some recovered when proper care could be restored to them, but many perished through this mishandling. We enjoy the undoubted benefits of having domestically bred fish available almost on demand now. These fish usually travel well and quickly pick up after their arrival and during their conditioning period prior to sale. A long finned strain exists, although the writer has only seen a few specimens in Thailand.

The Ruby shark has a similar history as the Red tail, in that today’s supplies are from farm bred stocks. When shipped to the market as wild caught fish years ago they were marketed as Red finned sharks and given a scientific name by the S.E Asian suppliers of Labeo erythrurus. The stocks we receive today are generally a much larger size than those of yester year, and a lovely albino strain has attained a deserved popularity. An albino strain of the Red tail also made its appearance a few years ago, but failed to gain any foothold in the popular market. Unlike the albino ruby shark the red tail was a wish-washy affair in stark contrast to its wild ancestoral stock and succeeding domestic strains.

Some interesting rarities with the “shark” label become available to the aquarium market from time to time. The Red spotted sailfin shark (Labeo rubropunctatus) is a large African species with a similar temperament to the Asian Black shark – quarrelsome, and often destined to live out a solitary aquarium existence.

The sail-like dorsal fin and deeply forked full tail fin, along with the red dotted scales, makes this an attractive species for the discerning specialist fishkeeper. But it is certainly not for everybody! The Small scale shark (Labeo rahita) from Thailand in another large sized fish, but in spite of its tough appearance it will co-habit with similarly big, stocky species without undue aggression. The scales are the outstanding feature of this species. They are a brassy basic colour, with a prominent black edging to each scale, and a red-to-orange colour suffusing the mid flank scales.

The Soldier river shark (Cyclocheilichthys enoplus) is a very stylish fish which only appears very occasionally, and then mostly by default. Odd juveniles might be received with Thai collections of other species more usually associated with the hobby. The mature fish carries a pointed dorsal fin which rises from a dorsal hump, and extends high above the body. The tail is deeply forked. The black edging accentuates the bright, shining silver spangles of every scale. This is a big restless fish, suited only to the really large aquarium. It is, however, surprisingly placid when given the right conditions. The Marbled shark (Labeo variegatus) is another African species which has become quite familiar to the aquarium hobby in more recent years. The basic colouring and markings can be very variable indeed, as the specific name suggests. This is frequently found to be an anti-social fish and its companions need to be tough enough to look after themselves.

More regularly seen are some of the Pangassius species, but their suitability to captive life has to be questioned, in view of their growth potential. Marketed as Tiger sharks, they are unusual as juveniles, and as such are attractive to fishkeepers searching for something different. The most frequently seen species is P. sutchi. The wild form has a burnished dark gun-metal basic colouring with darker longitudinal stripes. A domestically bred albino form also turns up frequently. This variety has none of the striping apparent, but is a pink and pearl all-over colour. This fish will grow to around 24″ given the right conditions. If you think that is formidable enough, then consider another species which has been coming onto the market as a “Hi-fin tiger shark”. This juvenile fish has a beautiful metallic burnished effect to its entire body, reflecting silver, gold, pearl, and bronze colours, topped by a sharply pointed black dorsal fin.

Very compelling for some prospective buyers. But wait a minute! What is this fish? It is Pangassius sanitwongsei, one of the world’s largest freshwater fish, found in the Mekong River of South East Asia. Reaching a record size of almost 10 feet in length it is unnecessary to spell out why this fish must be resisted by any average fishkeeper, and maybe considered by only those with a massively large aquarium or heated pool! The only large specimen I have seen was one of a group in a huge U-shaped aquarium which lines three walls of one room in Chiang Mai Zoo’s freshwater aquarium in northern Thailand. A relative baby, about 4 feet in length, it was an impressive fish, and already looking to be close to outgrowing its tank.

Not in the same league but another “Biggie” frequently offered to the hobby market is the Red finned cigar shark (Leptobarbus hoeveni). This is an attractive Asiatic fish which may grow to around 18 inches in length. The cylindrical body has black edged scales which reflect a spectrum of metallic colours. The ventral and anal fins carry quite a strong red colouring, which fades to a reddish tinge within the outer edges of the forked tail. This is one of several of the species labelled “sharks” which does not appear to have any features deserving of the name! As I suggested at the beginning of this article, the “shark” tag is undoubtedly a marketing strategy – and undeniably a successful one!

Similarly undeserving of the name, the handsome Festive apollo shark (Labiobarbus festiva) has much to commend it as an aquarium fish, however. The streamlined shape is beautifully complemented by the long-based dorsal fin and deeply forked, long-lobed, tail fin. Both fins have a strong red colour running along their full length, which is accentuated by black edgings. The silvery body carries a series of horizontal rows of black spots, evenly embellishing the entire body, save for the head back to the operculum and the underside.

The other Apollo shark is Luciosoma setigerum. Once again there is nothing about this species which is in any way suggestive of the archetypal “shark” of popular conception. Although an attractive fish in its own right, this species somewhat pales alongside its Festive companion. The lateral line is decorated with a row of alternating gold and dark green metallic “spots”, dividing the body laterally into a golden-green upper area and a silvery lower area. The lateral decoration blends finally into a black jet at the caudal peduncle, continuing into the upper lobe of the forked tail. A less distinctive black jet extends into the lower lobe of the tail. Undeniably a stylish fish, but does it really evoke shark-like images?

Water chemistry requirements will vary from “shark” to “shark”. Although all cyprinids they are taken from a variety of genera. However, in the writer’s experience they are easily adapted to a range of pH and hardness values for general keeping. Kept as a species in bespoke aquaria, established for optimum conditions, water chemistry factors will, of course, be more specifically addressed and fine-tuned to the species in question. Good, stable water quality, however, is essential, and the aquarium should be an established one, free of the volatility which might trouble an immature set-up. Breeding most of these species without the benefit of hormone stimulation, is a challenge. Stocks will rarely be purchased by hobbyists for this purpose. Remember, the commercial breeders of these species rely on hormone stimulation for their success. The freshwater “sharks” decorative virtues win most sales, with collectable status following some way behind. But whatever the reason for buying these stylish fish, there is much pleasure from owning one in prime condition, often becoming the jewel in the crown of a coveted living-picture home aquarium.

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