LINUTE THE BLACKTIP REEF SHARK
Linute, the blind blacktip reef shark
In the Indo-Pacific tank, which hosts “Cuba” - our Green Sea Turtle - and a Napoleonfish, you can also admire several specimens of Blacktip Reef Sharks, including Linute, who has an unusual and touching story.
The story of Linute, one of our Blacktip Reef Sharks, is common to many other exotic species, often acquired by people unaware of the conditions they need to be kept correctly in a controlled environment.
In his younger days, Linute lived for some time in a nightclub inside a tank that was far too small for him, and in surroundings that were too noisy and with unsuitably bright lights.
When Linute was liberated by the staff of Genoa Aquarium, in agreement with the competent authorities, he had eye injuries and a serious goitrous swelling of the thyroid gland, a sign of serious ill health due to the poor quality of the water.
He was taken to Genoa Aquarium, where veterinary care and scrupulous attention allowed him the return almost totally to perfect health. Sadly, however, he will always carry with him the signs of his former “home”, blind in both eyes, probably due to constantly knocking against the walls of his previous cramped tank.
Linute came to Livorno Aquarium in September 2011, and now swims freely in the Indo-Pacific tank.
Together with Carcharhinus amblyrhynchos and Triaenodon obesus, this is one of the commonest spark species of the Indo-Pacific reefs. The Blacktip Reef Shark dominates shallower waters, while the other two species mainly inhabit deeper waters. A fast and active swimmer, this shark can be encountered alone or in small groups, although larger aggregations have also been observed.
Adults and juveniles are mostly not sexually segregated, except in the case of females about to give birth, which leave the company of other sharks to bear their young alone. Individuals show a certain degree of faithfulness to their habitats, often spending many years of their life there.
A study off the Palmyra Atoll in the central Pacific has shown that these sharks live in an area of about half a square kilometre, with one of the smallest ranges of all shark species. The dimensions and location of this “home territory” does not change over the day, and within its confines, between 3% and 17% represents preferred hunting areas visited far more often than other zones.
These sharks spend most of their day swimming back and forth along the edges of the reefs, occasionally making brief excursions into sandy shallows. The average swimming speed decreases at night, when the tide rises, perhaps because the cooler water slows the metabolism, or because hunting becomes easier. Specimens at Aldabra seem to move over greater distances than those of Palmyra, with individuals recorded as having swum for up to 2.5 km in 7 hours.
A particular characteristic of this shark species is that it is one of the few that can jump out of the water with its whole body, known as “breaching”. It has also been observed when “spy hopping”, which is when it raises its head vertically out of the water to look around it. Sometimes, blacktip reef sharks, and in particular smaller specimens, fall prey to larger fishes like groupers, grey reef sharks and tiger sharks, and even adult sharks of their own species. At Palmyra, even larger blacktip reef sharks avoid tiger sharks, by keeping away from the deep lagoon at the centre of the island.
The Blacktip Reef Shark is often the most abundant apex predator in a local ecosystem, and it therefore plays a fundamental role in shaping its structure.
Its diet consists above all in teleost fishes of the coral reefs, such mullets, groupers, grunters, jacks, mojarras, wrasses, surgeonfishes and sand smelts. In the Indian Ocean, groups of these sharks have been observed herding shoals of mullet towards the shore, so as to be able to catch them more easily.
The diet of this shark can also include squids, octopuses, cuttlefish, shrimps and mantis shrimps, and more rarely dead animals and small sharks and rays.
Off the coast of northern Australia, this species has been known to eat sea snakes, including Acrochordus granulatus, Hydrelaps darwiniensis, Lapemis hardwickii and members of the Hydrophis genus.
At Palmyra Atoll, observers have noted attacks on seabird chicks that have fallen from their nests into the water. The stomachs of these sharks have also been found to contain residues of algae, seagrasses, corals, hydrozoans, bryozoans, rats and stones.
As with the grey reef shark, the individuals of this species become more excited and courageous in the presence of other sharks of the same species, and can be roused into s state of feeding frenzy. Feeding can also be more frequent at night.