Ice fish is known to many. This is a popular commercial fish species, which includes several subspecies. These fish differ in that they have colorless or white blood and can live for a long time at a temperature of several degrees below zero. That is why they are called ice. For its elongated muzzle and similarity to a common pike, the fish received the same name with the prefix “white-blooded”.
Initially, ice fish were not distinguished into a separate species or order and did not attach importance to the property of blood. At the beginning of the 20th century, scientists began to classify this species. The animals were well studied, described, and assigned to the perch-like order and the type of chordate fish. What does it mean that the body of fish is based on a chord or a prototype of the spine, which is evidence of the good development of the nervous system and brain of fish.
The fish has a powerful developed dorsal chord, strong jaws and radial long fins. The fins are located along the entire body and have a large number of hard rays. The two upper dorsal fins in some individuals may fuse into a single organ. The tail has a classic triangular shape with a notch. In young individuals, the tail and fins are light, in older fish they are darker.
Icefish are considered medium in size among other ocean dwellers. Its weight can be from 300 grams to 1.5 kg. Individuals of 3 kg are also found in the ocean, but this is rather an exception. The size of the whitefish is average – from 50 to 100 cm in length. The head is elongated, set high. The body has a classic shape for fish in the form of an ellipse, which is slightly elongated. The body has a good muscular structure.
The skin of the fish is covered with small, dense scales, dark, slightly bluish on the back and almost white on the belly. Because of this color, the fish looks like ice in the dark water of the ocean. On the whole body, the fish has wide, vertical dark stripes that look like highlights underwater. In the upper part of the body along the back, the animal has longitudinal lateral lines. There are no bone outgrowths on the skull or back.
The main feature of the species is the composition of the blood, in which there are practically no red blood cells and hemoglobin. This composition of the blood allows the animal to feel comfortable at a depth of 800 – 2000 meters and a temperature close to zero. Another feature of the animal is that breathing is not due to the gills, but due to the skin of the whole body. The peculiarity is also due to the frequent presence of fish at depth.
Habitat – the waters of the entire Antarctic from the islands of South Georgia to the Heard archipelago. In the southern part of Antarctica, large flocks of fish are found near the islands: South Georgia, the Sandwich Islands, the Shetland Archipelago. In the east, large populations can be found near the underwater Kerguelen Ridge. Here the fish lives at great depths. In the northern part, the fish lives mainly near the Arctic Peninsula.
The animal population is not evenly distributed across Antarctic waters. Schools of fish are found mostly near single islands and archipelagos. This is primarily due to the diet of fish and the possibility of spawning. Near the islands, the water depth is shallow; krill and small crustaceans are found in a larger volume here. Icefish can live freely here at depths of up to 500 meters.
Icefish feeds mainly on Antarctic krill, shrimps, crustaceans, small crabs and plankton. She can also eat squid, fry of different types of fish and other medium-sized animals. Because of this, the fish is considered predatory. Since crustaceans and krill are the basis of nutrition, fish meat has a characteristic shrimp taste, for which it is highly valued in cooking.
Despite its name, this fish is quite agile and very fast. This is primarily due to the peculiarities of the structure of the body and the environment. To keep such an animal alive in cold water, its heart works very powerfully, the rate of blood circulation throughout the body is very high. This maintains a high temperature compared to the environment. This is also the reason for the lively, mobile nature of the fish.
The fish lives in large schools, which is why it is very convenient for fishermen to catch it. But at the same time, the animal is very cautious, and at the slightest danger, the whole flock instantly goes to the depths, where it is difficult to find it for other predators or for fishermen to get it. At great depths, it can stay for a long time. Schools of fish have a well-organized structure. Different roles of individuals are traced: leaders, scouts, hunters.
Due to the fact that the fish lives in large schools, the main danger for it is the catch of nets in large quantities. Small schools of fish do not survive in the waters of the Atlantic, they cannot provide themselves with proper food or the necessary security from whales and other large animals. A high level of communication within the pack provides a quick message about danger or, conversely, about the opportunity to get food.
Individuals of this species have a sharp pronounced sexual difference. Females spawn in early autumn, males fertilize it almost immediately. Spawning takes place at a shallow depth, near the islands. A few months later, fry appear from the eggs, which stray into new flocks. Fish mature by two years, on average, each individual lives about 13-20 years, depending on the activity of natural enemies in the region.
The natural enemies of icefish are larger, predatory fish. From them, these animals are accustomed to defend themselves with cold and depth. They can easily withstand several days of staying at great depths at temperatures down to -5 degrees, where other large predators are not able to reach. A more serious danger to fish is a person who conducts a massive catch of these animals.
But according to scientists, even with a large catch of fish today, this species is not threatened with extinction. Icefish have virtually no natural enemies, can easily hide in cold waters, and are fed by a large population of krill. Due to the difficulties of catching fish, it is considered a delicacy, rare and very valuable. Therefore, ice fish does not need additional protective measures.
Ice fish is highly valued for its beautiful appearance, tasty, tender meat and high nutritional properties. It is considered quite rare due to its unusual living conditions and the remoteness of habitats from the main industrial centers of fish processing. The distance of transportation and the peculiarity of the catch also determine the high cost of carcasses on the shelves. It is for its rarity that it is valued among gourmets all over the world.