The cat shark is a genus belonging to the order Karhariformes. The most common and well-studied species of this genus is the common cat shark. It lives in the seas along the European coast, as well as off the African coast in layers of water from the highest to the bottom – the maximum habitat depth is 800 meters.
Origin of the species and description
The appearance of the most ancient ancestors of sharks is attributed to the Silurian period, their fossils were found in layers of antiquity of the order of 410-420 million years. A large number of life forms have been found that could become the ancestors of sharks, and it has not been reliably established from which of them they actually descended. Thus, despite a considerable number of finds of such ancient fish as placoderms and hybodus, the early evolution of sharks is poorly understood, and much remains unknown. Only by the Triassic period does everything become much clearer: at this time, species that are exactly related to sharks already inhabit the planet.
They did not survive to this day and were very different from modern sharks, but even then this superorder flourished. Sharks gradually evolved: there was calcification of the vertebrae, due to which they began to move much faster; the brain grew due to the areas responsible for smell; the jawbones were reshaped. They became more and more perfect predators. All this helped them survive during the Cretaceous-Paleogene extinction, when a significant part of the species that inhabited our planet simply disappeared. Sharks after him, on the contrary, reached even greater prosperity: the extinction of other aquatic predators freed up new ecological niches for them, which they began to occupy.
Video: Cat shark
And in order to do this, they had to change a lot again: it was then that most of the species that still live on Earth were formed. The first of the cat shark family, however, appeared earlier: about 110 million years ago. It seems that it is from him that the rest of the carchariformes originate. Due to such antiquity, many species belonging to this family have already become extinct. Fortunately, the common cat shark is not in danger of extinction. This species was described by C. Linnaeus in 1758, the name in Latin is Scyliorhinus canicula. Ironically, if in Russian the name is associated with a cat, then the specific name in Latin comes from the word canis, that is, a dog.
Interesting fact: When feline sharks are in danger, they inflate themselves by filling their stomachs. To do this, the shark arches into a U shape, grabs its own tail with its mouth, and sucks in water or air. When deflated, it makes a loud barking sound.
Appearance and Features
The length is small, on average 60-75 cm, sometimes reaches a meter. Weight 1-1.5 kg, in the largest individuals 2 kg. Of course, in comparison with really large sharks, such sizes seem very small, and these fish are sometimes even kept in aquariums. She still needs a large capacity, but her owner can boast of a real live shark, albeit a small one, but she looks like a shark. Although not so predatory, primarily because of the short and rounded muzzle. There are also no prominent fin lobes characteristic of large sharks, they are relatively underdeveloped.
The caudal fin is very long compared to the body. Cat shark eyes do not have a nictitating membrane. Her teeth are small and not sharp, but there are a lot of them, they are located row by row in the jaw. Males are distinguished by the fact that their teeth are larger. The body of the fish is covered with small scales, it is very hard, if you touch it, the feeling will be similar to touching sandpaper. The color of the cat shark is sandy, there are many dark spots on the body. Her belly is light, there are much fewer spots on it or none at all.
The coloration of other species, also belonging to the cat shark genus, may differ, as well as their length. For example, the South African species grows to 110-120 cm, its color is darker, and well-defined transverse stripes run along the body. Other species also differ: one rarely grows up to 40 cm, others grow to a rather impressive 160 cm. Accordingly, they have different lifestyles, behavior, nutrition, enemies – here, unless otherwise indicated, an ordinary cat shark is described.
Where does the cat shark live?
B mainly in waters surrounding Europe, including:
- Baltic Sea – relatively rare;
- North Sea;
- Irish Sea;
- Bay of Biscay;
- Mediterranean Sea;
- Sea of Marmara.
Also found along West Africa as far as Guinea. In the north, the limit of distribution is the coast of Norway, where there are relatively few of them, yet the water becomes too cool for this species. Does not live in the Black Sea, but sometimes swims, and is seen near the Turkish coast. In the Mediterranean Sea, this fish is most common near Sardinia and Corsica: presumably, in the vicinity of these islands there are territories where it breeds.
Another area of concentration of cat sharks near the western coast of Morocco. In general, they are common in temperate and subtropical waters, as they do not like too warm weather. They live at the bottom, and therefore they inhabit shelf areas where the depth is not great: they feel most comfortable at a depth of 70-100 m. But they can live both at a shallower depth – up to 8-10 m, and at a greater depth – up to 800 m. Usually, young sharks stay farther from the coast, at greater depths, and as they grow, they gradually move closer to it. When the breeding time comes, they swim in the sea to the very edge of the shelf, to where they themselves were born.
They settle in places with a rocky or sandy bottom, they like to stay in silty areas where a lot of algae and soft corals grow – this especially applies to juveniles. Other types of cat sharks can be found in various parts of the world, they inhabit all oceans. For example, several live in the Caribbean Sea at once: the Caribbean cat shark, the Bahamian, Central American. The Japanese is found off the east coast of Asia, and so on.
Now you know where the cat shark is found. Let's see what it eats.
What does a cat shark eat?
The diet of this fish is varied and includes almost all the small living creatures that it can only catch.
These are small organisms that live near the bottom, such as:
- polychaete worms.
But the basis of the menu of these sharks is small fish and decapods. As they grow, the diet pattern changes: young people mainly eat small crustaceans, while adults more often catch mollusks and large decapods and fish.
Their teeth are well adapted for cracking shells. Large cat sharks often prey on squid and octopuses – even an animal of comparable size to themselves can become their prey. Sometimes they are overly aggressive and try to attack even larger prey, and such attempts can end badly for them. The attacks themselves are usually made from an ambush, trying to catch the victim at the most inconvenient moment for her. If this does not work out and she manages to escape, the chase is usually not sent, although sometimes there are exceptions if the shark is too hungry. Also in these cases, she can eat the larvae of other marine life, although she usually ignores them.
The menu of the cat shark also includes plant foods: algae and several types of soft corals, which is why it often settles in areas rich in such vegetation. . However, plants do not play a large role in its nutrition. In summer, this fish eats much more actively than in winter.
Fun fact: Cat sharks respond to food rewards and seek them out by doing the same things they did before they were fed, researchers at Cranfield University have found. They remember this for a long time, up to 15-20 days.
Peculiarities of character and lifestyle
These sharks do not like the sun and, when it hangs high above the horizon, they prefer to rest on the bottom in shelters and gain strength. Underwater caves, heaps of snags or thickets serve as such shelters. Only when dusk falls do they begin to hunt, and the peak of their activity falls at night. At the same time, they do not have night vision, and indeed it is poorly developed, but rely on another sense organ. These are receptors (ampoules of Lorenzini) located on the muzzle. Every living organism that swims by inevitably generates electrical impulses, and sharks, using these receptors, catch it and accurately recognize the location of prey.
They are excellent hunters: they are able to make quick jerks, change direction abruptly, and have excellent reactions. Most of the night they swim slowly in the vicinity of their shelter at the bottom and look for prey. Small ones are attacked immediately, before attacking a large one, they can hide in ambush and wait until the best moment comes. Most often they hunt alone, but not always: it happens that they gather in flocks, primarily in order to hunt large animals together. But such flocks usually do not last long: most of the time cat sharks still live alone.
Sometimes several individuals live close to each other and get along well. There may be conflicts between cat sharks, and in such cases one of them drives the other away. Despite their rather aggressive nature, they are harmless to humans: their teeth are too small to cause serious damage, and they do not attack first. Even if a human swims too close and disturbs the cat shark, it will most likely just swim away and hide.
Social Structure and Reproduction
Cat sharks are predominantly solitary, rarely and briefly gathering in small groups, therefore, they do not have a social structure. They can spawn at any time of the year, most often it depends on the habitat. For example, in the Mediterranean Sea, spawning occurs in the spring, and in some individuals at the end of the year. In the north of their range, spawning begins in late autumn and can last until mid-summer; off the west coast of Africa, the first sharks spawn in February, and the last in August, and so on, this period can fall on a variety of months.
In any case, the female lays eggs no more than once a year. There are usually 10-20 of them, they are in hard capsules, very oblong in shape: they reach 5 cm in length and only 2 cm in width. At the ends of these capsules, threads up to 100 cm long, with their help, the eggs cling to something , such as a rock or seaweed. The development of the embryo inside the capsule lasts 5-10 months, and all this time it remains defenseless. At first, it helps that it is transparent, so it is very difficult to notice it in the water. Then, little by little, it becomes milky, and shortly before the end of the development period, it turns yellow, or even acquires a brown tint.
At this point, the fetus is at its greatest risk. Immediately after hatching, the length of the fry is 8 cm or a little more – interestingly, in cold waters they are larger than in warm ones. From the very first days they look like adults, only the spots are much larger relative to the size of the body. At first, they eat the remains of the yolk sac, but soon they have to look for their own food on their own. From this time on, they become small predators. They can spawn from the age of 2, by which time young cat sharks grow up to 40 cm. They live 10-12 years.
Cat sharks' natural enemies
Eggs and fry are most at risk, but, unlike their larger relatives, even an adult cat shark is not so large that it does not fear anyone in the sea. It is preyed upon by larger fish, primarily Atlantic cod – this is its worst enemy.
It has a significant superiority in size and weight, and most importantly: there are a lot of them in the same waters in which the cat lives shark. In addition to cod, their frequent enemies are other sharks, larger ones. As a rule, they are faster, and therefore the cat shark can only hide from them.
There are many who want to dine with them, so the life of these predators is very dangerous, and during the hunt they need to constantly monitor the situation around them so as not to accidentally become prey themselves. In addition to this, many parasites are among their enemies. The most common among them are kinetoplastids of several species, cestodes, monogeneans, nematodes and trematodes, copepods.
People are also dangerous for them, but not too much: they are usually not caught on purpose. They can be caught in nets or baited, but they are often released as the meat of these sharks is considered unpalatable. The cat shark is tenacious and, even if it takes damage from a hook, it almost always survives in such cases.
Population and species status
They are widespread and have a status of no concern. They have no commercial value, although, due to the large population and habitat at shallow depths, they are often caught as bycatch. This does not have a negative effect on the number, since most often they are thrown back into the sea. Although not always: some people like their meat, there are places where it is considered a delicacy even despite the smell. They are also used to make fishmeal and are valued as one of the best lobster baits. Still, the usefulness of the cat shark is quite limited, which is good for itself: the number of this species remains stable.
But several other species in the genus are close to vulnerable. For example, the stellate feline shark is actively caught, as a result of which its number in certain areas of the Mediterranean Sea has decreased to a minimum. The same applies to South African. The status of many species is simply unknown because they are little studied and researchers have not yet been able to establish their exact range and abundance – perhaps some of them are rare and need protection.
Interesting fact: To keep a cat shark in an aquarium, it must be very large: for an adult fish, the minimum is 1,500 liters, and preferably closer to 3,000 liters. If there are several, then for each next one you need to add another 500 liters.
The water should be cool, in the range of 10-16 ° C, and it is best if it is always one temperature. If the water becomes too warm, the immunity of the fish will suffer, it will often be affected by fungi and parasitic diseases, it will become less likely to eat. To get rid of parasites, sharks need to clean their skin, administer antibiotics and increase the level of salt in the water.
The cat shark is a small and harmless shark for humans, which is sometimes even kept in aquariums. Despite its modest size, this is a real predator, in general, it reminds everyone of its larger relatives – such a shark in miniature. It is on her example that researchers study the embryonic development of sharks.