Tropical Fish Hobbyist - October 2010

Natural History Those of us who have been keeping them for a while may remember the red-tail sharks as members of the genus Labeo, but axonomists have since deemed otherwise and several species are now classified under the genus Epalzeorhynchos. Many freshwater sharks still belong to the genus Labeo, a huge genus boasting far more species than you’ll ever encounter in your local fish shop. A third genus of freshwater sharks is Balantiocheilos. Because of their similar habitat requirements and generally similar dispositions, diets, and care in captivity, this article will only detail species in these three genera. Hailing from the warm, sluggish streams and waterways of southern Asia, these freshwater sharks have adapted in ways that are advantageous to a semi-predatory lifestyle. These fish are physically built for both speed and slow cruising: Powerful caudal fins can provide impressive thrust o aid a shark in making shorts bursts forward in pursuit of fleeing prey, or in long, continued marathons of swift escape from a would-be predator. Easily the fastest among these sharks is the very popular yet nervy bala shark Balantiocheilos melanopterus. Their long, flat, rigid pectoral and dorsal fins offer superb maneuverability and agility underwater: Should a partially hidden morsel of food catch their eye, or should a predator’s shadow loom suddenly over the waters, these fishes’ swift pectoral fins will angle upward and, with a swift flick of the caudal fin, steer them very quickly in the appropriate direction. Because of this adaptation, most freshwater sharks will often adopt a fast zig-zagging escape route to elude and confuse a predator.

their down-turned, carp-like mouths to rasp algae and detritus off underwater structures, these predominately bottom-feeders can survive on a diet of plant life and minuscule invertebrates. Their survival tactics do not end there, however, for many species of freshwater sharks—in particular, the red-tail shark Epalzeorhynchos bicolor and the black shark Labeo chrysophekadion—are also competent hunters of larger crustaceans and vertebrates such as fry, minnows, and small amphibians.

When food is particularly scarce, red-
tail sharks and black sharks have even
domains (usually a submerged tree stump
or tangle of rotting roots jutting from a
stream bank) from all comers. During the
mating season, females may travel from one
male’s domain to the next, and competition
between rival males can rise to a fever pitch.
Combat between any two fish (regardless
of the sex of the combatants) is also very
common during feeding; two fish that
happen upon the same morsel of food will
often become so entrenched in battling one
another that the food item either sinks or
swims away uneaten by either shark. Adult
sharks of many species (the red-tail shark,

MP. & C. Piednoir

Red-Tail Shark Perhaps the most attractive of all the freshwater sharks available in the pet trade today is the red-tail shark Epalzeorhynchos bicolor. As its common name suggests, this shark bears a vibrant crimson caudal fin and caudal peduncle, which offers stark contrast to the coal- to ebony-black body and fins. The only other color on this species, which does not occur in all specimens, is a white tip on the top of the dorsal fin. Average adult length is 4¾ inches, with specimens 5 inches and larger being especially handsome and impressive. Captive longevity may exceed seven years.

The red-tail shark Epalzeorhynchos bicolor is somewhat aggressive and cannot be housed with smaller fish.

Males are distinguishable from females only by the curvature of the dorsal fin: The male’s fin forms a sharper point at the top, and the posterior edge of the female’s dorsal fin forms a right angle with her body. A close examination of numerous fish should be enough to train the eye to recognize males from females. Both males and females become sexually viable around 15 months of age or 2½ inches in length.

Red-tail sharks require moderately large aquaria that afford plenty of hideouts and foliage the shark can claim as its own. Small

Feeding

All these sharks are omnivores. Employing
been known to consume the scales, fins,
and skin of other fish. A hungry shark
will swim beside its intended victim and
lunge suddenly sideways, inflicting a rapid
series of bites on the side or finnage of the
victim fish and swallowing any bits of flesh
that rasp off into its mouth. Slow-moving
or docile fish species may repeatedly find
themselves victims of a series of eat-and-run
attacks, for the slower fish make easy targets
for the lithe and swift sharks.