Over 500 different shark species inhabit the world’s oceans, but only a small percentage are suitable for exhibition in public aquariums. The public fascination with sharks drives aquariums to display them for educational purposes. However, the complex biological and logistical needs of these animals mean that successful long-term captivity is restricted to a select few species, balancing animal welfare with the facility’s capabilities.
Essential Criteria for Aquarium Suitability
The physical limitations of public tanks necessitate that a shark species cannot grow too large in its adult phase. A common rule-of-thumb suggests the habitat should be at least three times the maximum adult length and width of the shark, which rules out most large species. The animal’s temperament and social nature are also determining factors, as the shark must be non-aggressive toward tank mates and manageable for husbandry staff during maintenance and feeding.
Sharks must also demonstrate adaptability to the contained environment and the water quality of a closed system. Filtration must manage the heavy biological waste load produced by these carnivores, requiring high-capacity protein skimmers and robust biological filters. Furthermore, a species’ method of respiration is a significant constraint. Some sharks are “obligate ram ventilators” and must swim constantly to force oxygenated water over their gills, requiring large, unobstructed tanks for continuous swimming.
Commonly Exhibited Coastal and Reef Species
The most frequently and successfully maintained sharks are typically found in coastal or reef environments, often possessing a benthic, or bottom-dwelling, lifestyle. Nurse sharks (Ginglymostoma cirratum) are ideal candidates because they are naturally sedentary and are buccal breathers. This means they can actively pump water over their gills while resting motionless, removing the requirement for non-stop swimming and making them highly adaptable to confined spaces.
Smaller, active reef species like the Blacktip Reef Shark (Carcharhinus melanopterus) are popular, though they require significantly larger, open exhibits to accommodate their constant movement. Blacktips can reach lengths of about six feet and are strong, streamlined swimmers. This necessitates tanks with expansive, often circular, designs to prevent injury from repeated wall collisions.
Other smaller species, such as Leopard Sharks (Triakis semifasciata) and Bonnethead Sharks (Sphyrna tiburo), are also common choices due to their manageable size and dietary needs. The Bonnethead, a small hammerhead species, is notable for its specialized diet, which includes crustaceans and mollusks.
Challenges of Housing Large and Pelagic Sharks
The largest and most open-ocean, or pelagic, species present challenges that often push the boundaries of viability in captivity. Whale Sharks (Rhincodon typus), the largest fish in the world, have only been housed successfully by a handful of institutions globally, requiring tanks holding millions of gallons of water. The logistical demands of transporting these massive filter feeders and providing their specialized planktonic diet are immense, making their exhibition exceedingly rare.
Sand Tiger Sharks (Carcharias taurus) are relatively common in large aquariums because of their intimidating appearance and large size. They require very deep and spacious habitats to thrive. Their size, up to 10 feet, mandates a substantial investment in facility size and life support systems.
However, the Great White Shark (Carcharodon carcharias) remains virtually impossible to keep for extended periods. No individual has survived longer than a few months in captivity.
Great Whites are highly migratory, obligate ram ventilators that require vast, open-ocean territories, making even the largest man-made enclosures insufficient. Attempts to house them often result in severe stress, refusal to feed, and physical trauma as they navigate the tank’s boundaries. Their extreme sensitivity to electroreception means that magnetic fields generated by aquarium pumps and electrical equipment can disorient and distress them, contributing to their poor survival rate.