Katran is a small and harmless shark that lives in the coastal sea waters of various parts of our planet from Northern Europe to Australia. It has a commercial value and is caught in large quantities: it has tasty meat, and other parts of it also find use.
Origin of the species and description
Hybodus, which appeared in the Devonian period, are considered to be the ancestors of sharks. Paleozoic sharks looked little like modern ones, so not all scientists generally recognize their relationship. They died out at the end of the Paleozoic era, but probably gave rise to the Mesozoic, already quite clearly identified with modern ones.
Then the stingrays and sharks separated, calcification of the vertebrae occurred, as a result of which the latter became much faster and more dangerous than before. Thanks to the change in the jawbone, they began to open their mouths wider, an area responsible for the excellent sense of smell appeared in the brain.
During the entire Mesozoic, sharks flourished, at the same time the first representatives of the catranoid order appeared: this happened at the very end of the Jurassic period, 153 million years ago. Even the extinction that occurred at the end of the era did not shake the position of sharks, on the contrary, they got rid of large competitors and began to dominate the seas completely.
Of course, a significant part of shark species also died out, while others had to change – it was then, in The Paleogene era, the formation of most of the modern species, including the katrans, ended. Their scientific description was made by C. Linnaeus in 1758, they received the specific name Squalus acanthias.
Interesting fact: Although the katrans are safe for humans, they should be handled with care so as not to get hurt by their spikes. The fact is that at the tips of these spikes there is a weak poison – it is not capable of killing, but nevertheless unpleasant sensations are guaranteed.
Appearance and features
Their dimensions are small – adult males grow up to 70-100 cm, females are slightly larger. The largest katrans grow up to 150-160 cm. The weight of an adult fish is 5-10 kg. But they are much more dangerous than other fish of the same size.
Their body is streamlined, according to researchers, its shape is more perfect than that of other sharks. In combination with strong fins, this shape makes it very easy to cut through the water flow, maneuver effectively and gain high speed. Taxiing with the help of the tail, its movements allow even better cutting through the water column, the tail itself is powerful.
The fish has large pectoral and ventral fins, and spikes grow at the base of the dorsal fins: the first is shorter, and the second is very long and dangerous. The snout of the katran is pointed, the eyes are located in the middle between its tip and the first gill slit.
The scales are hard, similar to sandpaper. The color is gray, hardly noticeable in water, sometimes with a bluish metallic tint. Often white spots are noticeable on the body of a katran – there may be only a few or hundreds of them, and they themselves can be either very small, almost speckled, or large.
The teeth have one apex each and grow in several rows, the same on both the upper and lower jaws. They are very sharp, so with their help the katran easily kills prey and cuts it into pieces. The sharpness is maintained due to the constant replacement of teeth with new ones.
During the life of a katran, more than a thousand teeth can change. Of course, they are smaller than those of large sharks, but in other respects they are not much inferior to them, and are dangerous even for people – it’s good that the katrans themselves are not inclined to attack them.
Where does the katran live?
Loves waters of temperate and subtropical climatic zones, lives in them in various parts of the world. It is possible to single out several main habitats of katrans that do not communicate with each other – that is, separate subpopulations that differ from each other live in them.
- The western Atlantic – stretches from the coast Greenland in the north and along the eastern coasts of the Americas as far as Argentina in the south;
- eastern Atlantic – from the coast of Iceland to North Africa;
- Mediterranean Sea;
- Black Sea;
- coastal zone from India in the west through Indochina to the islands of Indonesia;
- west of the Pacific Ocean – from the Bering Sea in the north through the Yellow Sea, the shores of the Philippines, Indonesia and New Guinea to Australia.
As can be seen from the list above, they prefer not to swim in the open ocean and live in coastal waters, rarely moving away from the coast for long distances. Despite this, their area of distribution is very wide, they live even in the very cold waters of the Barents Sea.
They usually live within the same territory, but sometimes they undertake long-distance migrations: they are able to overcome several thousand kilometers. They move in flocks, migrations are seasonal: katrans are looking for water with the optimal temperature.
Most of the time they keep at a depth, the optimal layer of water for their life and hunting is near-bottom ones. They can dive to a maximum of 1,400 m. They rarely appear on the surface, this happens mainly in spring or autumn, when the water temperature is 14-18 degrees.
Seasonality can be traced in the choice of depth: in winter they go lower, to a level several hundred meters, because the water is warmer there and schools of fish such as anchovy and horse mackerel are found. In summer, they most often swim at a depth of several tens of meters: fish descend there, preferring cooler water, like whiting or sprats.
They are able to live permanently only in salt water, but for a while they can also swim in brackish water – they are sometimes found in the mouths of rivers, this is especially characteristic of the Australian population of katrans.
Now you know where the katrans shark is found. Let's see if it is dangerous for humans or not.
What does the katran eat?
Like other sharks, they can eat almost everything that just caught their eye – however, unlike their larger relatives, some fish and animals turn out to be too large and strong for them, so hunting for them has to be abandoned.
The usual menu of a katran often includes:
- bony fish;
- sea anemones;
Although the katrans are small, their jaws are designed in such a way that they are able to hunt fairly large prey. Medium-sized fish should beware, first of all, not of large sharks, but of katrans, these fast and nimble predators with an insatiable appetite. And not only medium ones: they are able to kill even dolphins, despite the fact that they can reach a larger size. Katrans simply attack in a whole flock, so that the dolphin cannot cope with them.
A lot of cephalopods die in the teeth of katrans, which are much larger than other large aquatic predators near the coasts. If large prey is not caught, the katran may try to dig something at the bottom – it may be worms or other inhabitants.
He is also able to eat algae, this is even necessary to obtain some mineral elements – but still prefers to eat meat. To feast on them, it can even follow shoals of forage fish for thousands of kilometers.
They love katrans and eat fish caught in the net, so fishermen are missing a considerable part because of them in the waters where they live a lot . If the katran itself got caught in the net, it is often able to break it – it is much stronger than the usual fish for which the net is designed.
Character and lifestyle features
They live in packs, they can hunt both during the day and at night. Although, unlike most other sharks, they are able to sleep: sharks need to constantly move in order to breathe, and in katrans, the swimming muscles receive signals from the spinal cord, and it can continue to send them during sleep.
Katran not only very fast, but also hardy and can pursue prey for a long time if it was not possible to catch it right away. Hiding from his field of vision is not enough: the katran knows the location of the victim and strives there, literally, he smells fright – he can catch the substance released due to fear.
In addition, the katrans do not care about pain: they simply do not feel it, and can continue to attack, even when they are wounded. All these qualities make the katran an extremely dangerous predator, besides, it is also hardly noticeable in the water due to its camouflage color, so it can get very close.
Life expectancy is 22-28 years, in some cases it can live much longer : they die most often due to the fact that they are no longer as fast as in their youth, and they simply do not have enough food. Long-lived katrans can last 35-40 years, there is evidence that in some cases they managed to live up to 50 years or more.
Interesting fact: The age of a katran is easiest to determine by cutting off its thorn – annual rings are deposited inside it, just like trees.
Social structure and reproduction
The mating season begins in the spring. After mating, eggs develop in special gelatinous capsules: in each of them there can be from 1 to 13. In total, the embryos are in the body of the female for about 20 months, and only by the autumn of the next year after conception, fry are born.
Among all sharks, katrans have the longest pregnancy. Only a small part of the embryos survives to birth – 6-25. They are born with cartilaginous covers on spines, necessary for the mother shark to stay alive during childbirth. Immediately after them, these covers are discarded.
The newborn sharks are 20-28 cm long and can already stand up for themselves at least against small predators, but still, most of them die in the first months of life. At first they feed from the yolk sac, but they quickly eat everything and they have to look for food on their own.
Sharks are generally extremely voracious, even more than adults: they need food to grow, and besides, they spend a lot of energy even on breathing. Therefore, they need to eat constantly, and they absorb a lot of small living creatures: plankton, fry of other fish and amphibians, insects.
By the year they grow strongly and there are much fewer threats to them. After that, the growth of the katran slows down and it reaches puberty only by 9-11 years. The fish can grow until death, but it does it more and more slowly, because there is no significant difference in size between the katrans of 15 and 25 years old.
Natural enemies of katrans
Adult katrans can only be threatened by killer whales and larger sharks: both are not averse to eating them. In confrontation with them, the katrans have nothing to count on, they can only injure killer whales, and even then quite weakly: their teeth are too small for these giants.
It is also a disastrous thing for katrans to engage in fights with larger sharks. Therefore, when meeting with them, as with killer whales, it remains only to turn around and try to hide – fortunately, speed and endurance allow us to count on a successful flight. But you can’t delay with this – you just have to gape, and you can end up in the teeth of a shark.
Therefore, the katrans are always vigilant, even when they are resting, and are ready to run. They are in the greatest danger when they themselves hunt – their attention is focused on the prey, and they may not notice how a predator swims up to them and prepares to throw.
Another threat is a person. The meat of katrans is highly valued, it is used to produce salmon and canned food, and therefore they are caught on an industrial scale. Every year, people catch millions of individuals: most likely it is much more than killer whales and all sharks combined.
But in general, it cannot be said that an adult katran faces many dangers, and most of them live successfully for several decades: however, only if they manage to survive the first years of life, because they are much more dangerous. Fry and young katrans can be preyed upon by medium-sized predatory fish, as well as birds and marine mammals.
Gradually, as the threats grow, it becomes less and less, but the katran itself turns into an increasingly formidable predator, exterminating even some of the animals that threatened it earlier – for example, predatory fish suffer from it.
Interesting fact: Although the meat of the katrans is tasty, it should not be overly carried away, and it is better for small children and pregnant women not to eat it at all. It's just that it has too much heavy metals, and too much of them is harmful to the body.
Population and species status
One of the most widespread species of sharks. The seas and oceans of the world are inhabited by a very large number of katrans, so nothing threatens the species, they are allowed to be caught. And they do it on a large scale: the peak of production occurred in the 1970s, and then the annual catch reached 70,000 tons.
In recent decades, the catch has decreased by about a third, but the katrans are still very actively mined in many countries: France, Great Britain, Norway, China, Japan, and so on. The zone of the most active catch: the north Atlantic Ocean, the largest population lives in it.
They are so actively caught because of their great economic value:
- the meat of the katrans is very tasty, it does not have the smell of ammonia, which is characteristic of the meat of many other sharks. It is consumed fresh, salted, dried, canned;
- medical and technical fat is obtained from the liver. The liver itself can be up to a third of the weight of the shark;
- the head, fins and tail of the katran go to the production of glue;
- an antibiotic is obtained from the lining of the stomach, and osteoarthritis is treated with a substance from the cartilage.
The caught katran is used almost entirely – it is not surprising that this fish is considered so valuable and is actively fished for. However, production has declined in recent decades for a reason: despite the fact that there are still a lot of katrans on the planet as a whole, in some regions their numbers have greatly decreased due to overfishing.
Katrans hatch for a very long time cubs, and it takes them a decade to reach sexual maturity, so this species is sensitive to active fishing. Since there were a lot of them before, it did not become clear right away. For example, in the USA, they were previously caught in tens of millions, until it was discovered that the population had decreased significantly.
As a result, now there, as in some other regions, there are quotas for catching these sharks, and when they are caught it is customary to throw it away as bycatch – they are strong and in most cases survive.
Katran is a living illustration of the fact that even an extremely common animal, a person is able to lime, if taken properly. If earlier there were a lot of them off the coast of North America, then as a result of overfishing, the population was seriously undermined, so it was necessary to limit the catch.