The 1.4-million-litre great pool, with the 13-meter-long observation tunnel and two viewing windows of 9x4 metres each, houses 8 sharks. Sharks, like rays, belong to the chondrichthyes within the class of fish. They differ from teleosteans in several anatomic and physiological features:

their scale armour consists of special scales that look like tiny, sharp “teeth”, lending rasping, scrappy feel to the shark skin. Unlike the teleosteans, the basic skeleton of their body is cartilaginous (which is nowadays believed to cure cancer and other diseases, creating yet another reason to hunt sharks) and their tail fin is asymmetrical. Their teeth are organised in several rows without teeth-ridges or roots. This means that they easily fall out but the teeth situated behind the lost ones move forward, filling up the gap. This is what we call a revolver denture. For instance a sand tiger shark can loose as many as 10.000 teeth a year. These fish do not have swim-bladders like the teleosteans, so while a carp can ascend and descend in the water without using any energy, sharks have to use their muscles. However, certain species, like the sand tiger shark, swallow water as they reach the water surface, and then they can control their descend by releasing it. They do not have gill-flaps, only gill-openings, separated by muscle sheets. Therefore, they have to swim unceasingly with their mouth open in order to have fresh water full of oxygen flow through their gills. If they stop swimming, they immediately sink to the bottom as they do not have swim-bladders and they drown. This is why a shark dies so quickly if it gets entangled in a fishing net, with the exception of only a few species. They multiply through internal insemination, i.e. the male animal has external genitals, in the form of two penises. In case of 99% of the teleosteans, the female lays the roes, which the male then inseminates outside the female’s body.

Sharks use different sense organs to find their prey, sensing

• sounds and smell from more than 500 metres,
• vibration from around 50 metres,
• sights from around 50 metres,
• electric signs from around 0.5 metre and
• tastes from 0 metre.

We present 4 species in the grand aquarium of the Tropicarium.

Brown shark
Occurrence: In the Atlantic Ocean from Massachusetts to Brazil. Habitat: continental shelf areas, shallow waters near the coastline, river estuaries and coral reefs. Food: fish, crabs, rays, molluscs and other smaller sharks; like most other sharks, they hunt mainly at night and do not particularly like the flesh of mammals and fresh water fish. Size: female – 2.2-2.5 metres, male – 1.8 metres.
Multiplication: viviparous, they give birth to 8-10 offspring after gestation period of 12 months and they become mature at the age of 15 years. An interesting fact: this species makes up 66% of all the fish caught industrially on the Eastern side of the USA. Its tail fin is large, compared to its body. They make huge distances; some sharks have been observed to travel as long as 2800 km at a time.

Sand tiger shark
We have four female and one male animal. Its name refers to the fact that it looks like the ‘big’ tiger shark but it stays much smaller. The largest caught fish was 3.18 metres long but they generally only grow 2-2.5 metres. It inhabits the warm waters of the Indian and the Pacific Oceans. Due to intensive hunting, their numbers decreased so dramatically at the Australian coast that they have been declared protected. Their special feature is that, unlike most other shark species, they often hunt in large groups. They are also viviparous and they have a curious speciality: cannibalism inside the uterus. The conceived 20-60 embryos are not separated by egg membrane and the 2 strongest offspring devour the others inside their mother’s body. Therefore, only 2 sharks are born but they are 1-1.2 metres long, which is quite large, considering the 2-2.5 metre-long body of the mother.

Leopard shark
The leopard shark couple arrived to our aquarium in March 2004. They originate from the coastal waters of Australia. Their maximum size may reach 3.5 metres but they rarely grow longer than 2.3 metres. They live around the coral reefs and generally live alone, only forming larger groups in the mating season. During copulation, the male animal clings on to the female’s breast-fin, thus stabilising itself. They belong to egg-laying sharks, attaching their eggs of brown or purple colour to the corals. The shark babies leave their eggs after 170 days, when they are 25 cm long. This shark species mainly feeds on snails, shells and crabs that live on the bottom, opening them up using its three-peaked teeth. Leopard sharks are often followed by striped cleaning fish, which partly relieve them from the parasites and also function as toothbrushes as they remove the food remnants from between their teeth. This ‘cohabitation’, which is equally beneficial for the sharks and the cleaning fish, is called symbiosis. Although the photo shows the shark lying on the bottom, it spends most of its time swimming in the upper regions of the pool. Perhaps we can say that they are the favourites of the divers feeding the sharks as they have a huge appetite and they are also very friendly. Leopard sharks are not only fed by the divers; caretakers serve them calamaries and other fine food several times a week.

Bessy, the sicklefin lemonshark, arrived from the 4.000-litre aquarium of a private collector in Bratislava to the Tropicarium, where it received a 15.000-litre new home.
Bessy saw the light of day in the waters of Sri Lanka around 2 years ago. She is now 1.2 metres long. Bessy is a real ‘wildcat’; her body is graceful and muscular, she swims fast in the water and keenly watches her environment, which is no surprise as this species is known as a successful hunter, When she grows, she may reach a length of 3.8 metres and weigh several hundred kilos. In the Tropicarium we feed her – just like the others – with octopus pieces and mackerels before the big ones, although she would prefer to ‘taste’ the smaller sharks and the rays.

Shark feeding
The Tropicarium’s well-qualified caretakers with diving certificates weekly submerge in the 4-metre-deep pool with nearly 1.4 million litres of 21-23°C water. While diving, they feed the animals from their hands and clean the aquarium. The caretakers give the predators about 12-15 kg sea fish at a time. They feed the animals twice weekly (once underwater and once from the surface) but the sharks still hunt instinctively during the night and catch a smaller fish or two in the huge aquarium. Diving takes place each Thursday between 3 and 4 p.m., apart from a few special cases.