Triakis semifasciata (Leopard shark)

Triakis semifasciata swimmimg over a Blue Ribbon eel in Mike Iannibeli's tank.

Family Scyliorhinidae, true Catsharks, Swell Sharks, particularly the genus Cephaloscyllium. With fifteen species and some 111 described species, you'll have to check to make sure the one's you're looking at are tropical and stay small enough.

Hornsharks (with two dorsal spines), aka Pig, Bullhead, Port Jacksons, family Heterodontidae. Tropical members of the family Heterodontidae, Horn sharks. Look for Heterodontus zebra and H. portusjacksoni. One genus, eight species.

    Note there are some suitable tropical specimens in this family. Do avoid the most often offered Hornshark, Heterodontus francisci from California.

Wobbegongs or Carpet Sharks, family Orectolobidae. Family Orectolobidae, the Carpet Sharks or Wobbegongs. Bizarre, dorso-ventrally flattened with camouflaged markings and flaps of skin. Most offered species are true tropicals. Pricey, but hardy specimens (expect to pay a couple hundred dollars plus for a captive shark). Favored genera are Orectolobus and Eucrossorhinus.

    Beautiful and odd-appearing, and too appealing to aquarists' eyes, therefore offered regularly in the aquarium trade, though too big and livestock-eating for captive use. Six species in three genera in the West Pacific.

My Take on the Too-Big-For-Aquarium Use Sharks 

Nurse Sharks, family Ginglystomatidae. Coastal Atlantic, Pacific, Indian Oceans. Three genera, each with one species. All too big for aquarium use...  Nurse sharks. Probably the most popular, frequently offered shark in the U.S. as it occurs commonly along the Eastern seaboard Rhode Island to Brazil. Their only real downside is that they get big (maybe fifteen feet), quick (a foot or two a year). Feed sparingly, infrequently.

My Pitch on Coldwater Specimens: 

Don't. Here we're referring to sharks that are collected in below room temperature water. This is one of the areas I diverge from most other shark-aquarium writers. Unless you're committed to providing a very large system with adequate cooling, shy away from the following animals. Though often offered, cool water sharks generally fare poorly. Who are they? Many more species than you may be aware of are collected from cool/cold water and offered as tropicals... see below.

Most of the smooth hounds and Dogfishes, family Squalidae, and Leopard Sharks, family Triakidae in the trade are coldwater. Lastly another native, the Pacific Angel Shark, Squatina californica (Family Squatinidae).

Smoothhounds, Dogfish (hey, that's me!), families Triakidae (see below) and Squalidae: Two genera, eleven species. 

Houndsharks, family Triakidae: eastern, western Atlantic, Indian and Pacific Oceans. Nine genera, 39 species.

My Pitch re "Real" Sharks:  

You know the super streamlined "Jaws" types. Every now and then, dealers can pick up Requiem Sharks (Family Carcharhinidae) like the Lemon (Negaprion brevirostris), Black-Tips and even Makos (family Lamnidae), and Hammerheads (family Sphyrnidae) are occasionally offered. Leave these in the sea. They require humongous facilities and mucho care.

Requiem Sharks, Family Carcharhinidae. Marine, some fresh. Atlantic, Pacific, Indian. Twelve genera, 50 species.

Hammerhead Sharks, family Sphyrnidae:

Collecting Your Own 

Is not recommended as being overly dangerous to shark and collector. Allow me this chance to mention the speed and elasticity of these fishes. Many years ago (when Paul McCartney was with the Beatles) I was a scuba diving instructor. On one check-out dive at San Diego's La Jolla Cove, my co-instructor came upon a four to five foot angel shark (Squatina californica), lying semi-buried on the bottom. Wanting to bring the shark's presence to his students' attention, he semi-wittingly grabbed the shark by it's tail. It promptly spun around one-hundred eighty plus degrees and bit off the end of his flipper.

A few further notes here concerning handling sharks. Be extremely careful. They are faster than you. Prior to the advent of good adhesives, shark skin was used as an abrasive, and for shoe tips due to it's sturdiness... shark skin is embryologically derived from the same tissue as their teeth and is very similar structurally. Some sharks have venomous spines; have I mentioned that they bite indiscriminately?

Is this clear enough? You are not going to bop a shark on the nose to prevent it from biting; if it's big enough it may bite your arm off at the elbow. You are not faster than even the tiniest, youngest shark.

Damage to internal organs from mis-, or any handling is a major cause of shark death. Shades of Flipper (Tursiops truncatus)! You've probably heard tales of dolphin butting-induced killing of sharks. Turns out sharks lose attachment (herniate) easily by being struck. If/when you have to move one: 1) wear gloves, 2) "Scoop" the specimen into a suitably large and strong plastic bag(s), and 3) get help with lifting and placing into a 4) styrofoam or other soft-sided carrier.

When selecting a specimen, watch out for blood streaking, primarily along the underside. This may be symptomatic of physical injury or resultant bacterial infection. Other than metabolite poisoning, psychological dis-ease; both from too-small a system, secondary infection has got to be the next most common source of mortality.

Environmental: Conditions

Habitat

First of all the obvious, the bigger the tank, the better; with a beefy, high flow rate (two plus turns per hour) filtration system. You must have a functioning skimmer.

Less "show tank" shape and more flat and shallow; ideally with rounded (mega-hex?) corners, otherwise minimized physical barriers to swimming around. Optimize surface area.

Conceal tubes, heaters, airlifts, filters, to prevent run ins, pull ups, tunneling, breakage...

Finer, less angular gravels are preferred to avoid scraping. Dolomite, marble are out; fine, crushed coral sand is ideal.

Chemical/Physical:

Here is you have a great opportunity to enhance your amazement and appreciation for the diversity of fishes. Sharks have some peculiar (to their group) needs compared to what you're probably familiar with.

Salinity should be kept high, near worldwide sea level, @ 1.025 specific gravity, and constant. Reason? Sharks (actually all chondrichthyan fishes), unlike bony fishes are semi-isotonic (equal in concentration) with the percentage of certain charged materials (like salts) in their general environment. To some degree they manipulate nitrogenous waste metabolism and excretion with the make-up of the surrounding water... you get the point. Large, regular water changes of the same specified specific gravity will get you by.

Monitoring and avoiding metabolic waste bottle-necking should be paramount. Sharks are large, metabolically active animals. How many pounds/kilograms, make that ounces/grams of fishes do you maintain now? Humbling, isn't it? Check out the smallest sharks available; one most likely weighs in at more than all the fishes you've ever kept total. The need for good circulation, regular maintenance, over-engineered and built filtration is clear.

About metal of any sort in the system: to be avoided at all costs. Ferrous (iron bearing) matter is especially problematical. Sharks possess an acute electromagnetic sense associated with pit organs located beneath their heads (the ampullae of Lorenzini). Other metals in solution cause sharks to go anosmotically off-feed. Remove metal, even plastic or glass-encased from the system and sump, out of harm's way and to reduce affecting your shark.

Even metal rebar (reinforcing steel) cast into concrete walls in public aquariums has been indicted as "driving these fishes crazy", resulting in their deaths.

Filtration

My usual endorsement for marine systems cannot be more emphatically re-stated here: I would not have a marine system without a functioning protein skimmer. With such large animals as sharks, processing so much proteinaceous material (food), a foam fractionator is an absolute necessity in a closed system. Enough said, or written, I trust.

As regards standard formats for metabolite conversion, the most efficient fluidized bed, and wet-dry technologies are favored, with rapid sand and more conventional canister filtration being just barely adequate. undergravel filtering is not endorsed at all; the metabolically active surface area is too small to be practical and too easily disrupted.

Display

If you must have decor, restrict it to some central area to keep the swimming perimeter clear. Be aware that sharks are diggers and will undermine your artistic edifices; build accordingly.

 Behavior: Territoriality

Though known to chomp on their own or other shark species in a feeding frenzy, most accounts show captive sharks steady eaters of the foods they've been trained on and not each other.

For hobbyists, there are exceedingly few systems that are large enough to consider having more than one shark specimen. Sharks will try to eat any invertebrate, or other fish if hungry, or maybe just curious. I have dissected dozens of large sharks, finding cans, crabs, rocks, bicycle parts, jewelry, etc. in them.

Introduction/Acclimation

Is simple enough. You are encouraged to place your shark only in a "seasoned", read that as "old" system. One that has been time tested with another fish.

Predator/Prey Relations:

Most sharks are fine with other species providing they are not mouth-size or slow-moving. Surprisingly, rather than the perpetrator, your shark may be the victim of harassment by it's tankmates. Large angelfishes, triggers, puffers, et al. are recorded as opportunistic shark pickers.

Reproduction, Sexual Differentiation/Growing Your Own:

Sharks have an astounding reproductive biology. Different species lay eggs, give birth live with and without umbilical-like attachments; with surprisingly long gestation periods and low birth rates. If you're going to invest the money to try one out, put in the time to investigate the way the sharks make their life.

All utilize sex, that is internal fertilization, granting an easy manner of determining whether you are looking at a male or female. Males possess claspers, specialized tube-shaped pelvic fins for genetic transmission. The pelvics of females are more triangular shaped.

Locomotion:

Sharks move about and aid their blood circulations by throwing their bodies into sinusoidal curves. They lack swim bladders, but to some degree compensate for the lack of a gaseous hydrostatic mechanism by their possession of relatively large, fatty livers (which float). Most sharks also utilize hydrostatic lift, capitalizing on having more surface area on their upper bodies than lower, staying in constant motion. The induced drag results in a "lift". Tail (heterocercal, with a larger upper lobe), pectoral fin shape also add lift.

The practical implications of their mode of transport is that sharks need lots of room, can't change direction or level easily, and hate square system corners.

Biology/Other: 

All sharks are talented jumpers, aquatic Houdinis at escaping through the smallest of openings; even knocking off the heftiest of covers. You must have a serious top to keep your shark in.

Regarding sharks' being idiots; they're not. Though selachian brains are tiny, sharks are amazingly well hard-wired to do what they do, and capable of substantial learning. I have witnessed wide "discrimination" and retrieval behavior in nurse sharks first hand.

 Feeding/Foods/Nutrition: Types, Frequency, Amount, Wastes

The species of sharks that are suitable for aquarium keeping are typically hearty eaters, once adjusted to their quarters. Food strikes, however, are not uncommon, especially for newly imported sharks. Try feeding at night or live food if one of these bouts stretches on; a few weeks for a juvenile to not eat is not a huge problem... if the individual is "well-fleshed"; that is, not sunken in. This "good" "index of fitness" is best assessed by examining the animal head on. Behind the eyes the area should appear convex, not concave.

Frozen foods are preferred by aquarists being less expensive, easily stored and removed if uneaten. My favorites are silversides, krill and cleaned shellfish. Squid is widely accepted but can be messy. vitamin supplements are endorsed by all experienced shark people and administered by every public aquarium. 

Don't overfeed! Offering food two, three times per week is adequate. Sharks are known to eat infrequently in the wild. This warning against overfeeding can't be stated strongly enough. Too much, too often leads directly to two bad situations; poor water quality and a large specimen. Offering food two, three times per week is adequate. Sharks are known to eat infrequently in the wild. This warning against overfeeding can't be stated strongly enough. Too much, too often leads directly to two bad situations; poor water quality and a large specimen.

Don't handfeed! Besides the obvious and very real danger of a nasty laceration from biting, there is an increased risk of introducing pollution. Instead, train your shark to "stick" feed with the food skewered on a plastic rod.

I will dispense with regaling you with anecdotes of the tremendous suction power of Atlantic nurse sharks (Ginglymostoma) among other disasters. Keep your hands out of the tank as much as possible.

Disease: Infectious, Parasitic, Nutritional, Genetic, Social

Sharks do very poorly if and when treated with many standard remedies. Copper compounds are deadly as are many dye solution treatments. I likewise strongly differ with some authors who endorse the use of organophosphate pesticides. Please see my self-cited piece on DTHP use. This bug-spray ingredient is common in several preparations worldwide under various names (masoten, dylox, neguvon, among others).

Reddening due to irritation and possible Vibrio bacteria may be treated with chloramphenicol (if you can still get it) or tetracycline administered internally via a food bolus.

I'm rather hesitant to mention freshwater and formalin baths for blatant external parasite extermination. Often the damage to the shark (and you!) from thrashing about is greater than any good the dip might do. Be careful, and follow the above recommendations in handling.

Sharks and their relatives are host to many worm, crustacean and protozoan parasites. The best way to avoid problems with them is to do your best to purchase a clean, healthy specimen, give it good care, and prevent introducing these parasites. The last is best accomplished by not using live or fresh seafoods; use frozen or freshwater instead.

Summary:

Difficulties in captive care of sharks are several including the need for large, highly filtered systems, poor adaptability in terms of behavior for most open-water species, and oft-neglected chemical and physical environmental insults; in particular keeping cold to cool water species in warm to tropical temperatures, treating sharks with metal solutions and organophosphate containing remedies, and not maintaining a high, stable salinity. A consistent light regimen and the absence of metal in the system are absolute requirements for successful shark keeping.

Many other authors have falsely informed, glossed over and/or omitted mention of these considerations to the enterprising wanna-be shark-aquarist, to their and their specimens detriment. It is my anecdotal experience that the average shark captive life is less than a month, most succumbing from the effects of being housed in too small an aquarium, mis-handling or treatment-poisoning.

The few species promoted in this article for hobbyist captivity are known to tolerate the vagaries and limitations of small aquarium systems. Most others should be left in the seas and lakes of their origins, excepting those specimens sacrificed for ornament and research in public exhibition. Far from "voracious, killing-machine" top predator status, sharks occupy many important niches, from truly giant plankton sievers to the ever-needed clean-up jobs of ensuring "fitness" by eating the weak and diseased. Of the few varieties that have been studied thoroughly, they are known to have low birth rates, relatively long generation times and modest population densities. As a group they are far from deserving our unrestrained enmity, wanton destruction from fear of attack, fin collection, or even the minimal casual loss due to inadequate aquarist husbandry in selection and care.

Bibliography/Further Reading:

Axelrod, H.R. 1975. Something About Sharks. T.F.H. 3/75.

Fenner, Robert. 1988. Pond Parasite Control with DTHP. Rinko (Japan), 2/88, FAMA 11/89.

Debelius, Helmut. 1978. The blue-spotted ray, Taeniura lymna. TFH 10/78.

Glodek, Garrett A. 1992. Shark Biology Pts I & II, FAMA 3, 4/92.

Hemdal, Jay. 1986. The banded catshark. FAMA 6/86.

Henningsen, Alan D. & Forrest A. Young. 1988. The Florida Scene (writing on lemon sharks). Marine Fish Monthly, 3(8):88.

Kerstitch, Alex. 1984. The birth of a shark. FAMA 5/84.

Lambert, Derek. 1994. The livebearer world; forgotten livebearers: the stingrays. TFH 12/94.

Lynch, James. 1994. Shark Watch; the Catsharks. T.F.H., 11/94.

Michael, Scott W. 1986. Sharks for Your Saltwater Tank. Pt I, II, FAMA 10, 11/86

Michael, Scott W. 1990. Sharks and rays in the home aquarium, parts 1,2. AFM 10,11/90.

Michael, Scott. 1991. The Sharks of the family Hemiscyllidae: The Bamboo & W. Epaulette Sharks. SeaScope, Fall 91.

Michael, Scott. 1995. Nurse Sharks (Not as good an idea as it might seem). AFM 1/95.

Michael, Scott. 1999. Wobbegongs (Family Orectolobidae). These fish are not for everyone. AFM 10/99.

Nelson, Joseph S. 1994. Fishes of The World. 3rd Ed. John Wiley & Sons, NY & the World.

Olmstead, John A. 1985. A nurse shark in the home aquarium. FAMA 4/85.

Perrine, Doug. 1994. Shark Fishing. Scuba Times. 12/94.

Roth, Allan. 1986. Sharks: Recent Advances in Captive Biology. FAMA, 5/86.

Scopes, Jack. 1994. Keeping Sharks: What You Need To Know. FAMA 12/94.

Spencer, Gary A. 1976. Living Room Sharks. Marine Aquarist 7:4(76).

Stevens, Jane E. 1995. The delicate art of shark keeping. Sea Frontiers, Spring 95.

Thorson, Thomas B., ed. 1976. Investigations of the Ichthyofauna of Nicaraguan Lakes. Univ. of Nebraska, Lincoln.

Wisner, Martin. 1987. Collecting and transporting black tip reef sharks. FAMA 10/87

With the permission of Robert (Bob) Fenner webmaster of WetWebMedia (bobfenner@aol.com) Photo by Mike Iannibeli (with permission)