Characteristics of the Fish

The characteristics of the fish are very diverse among themselves, according to the species in question. Fish are marine vertebrate animals, which breathe using their gills, which allows them to breathe underwater.

These creatures are born in the water, they live in both fresh and salt water, and any water reservoir represents a habitat for these animals. But depending on the characteristics of the water, specific species are developed that adapt to said environment.

Fish play a fundamental role in human life, because it is an important source of protein;  which means a vital link for human nutrition. Experts say that there are more than 21,000 different species of fish, some edible and others not.

Fish are ectothermic, because their bloodstream can adapt to the temperature of the water; which means that the fish that is in a pond or a stream, its blood can become lukewarm; but fish from rivers or from polar regions such as glaciers are quite cold-blooded.

They also have scales, it is one of the most distinctive qualities of these animals; however, there are species of smooth-skinned fish such as catfish, eels, swordfish, and sharks.

Types of fish according to their physical characteristics

1. Fish with scales: the vast majority of aquatic animals have scales that cover their skin; scales are a shield that protects your skin from potential aquatic hazards, such as bacteria, fungi, or shock damage; such as the damage that some predators can cause;  these vary in size and shape depending on the fish, but are generally rounded and iridescent in color. The location of the scales on the body of the fish facilitates their hydrodynamic displacement.
2. Fish without scales: as we mentioned before, there are several species of fish. Characteristics of the Fish that do not have scales; just as there are marine animals that look like fish but are not; as is the case with whales and dolphins, which are mammals.  These neither have scales nor do they have gills; their respiratory system consists of one or two spiracles through which they breathe the air that reaches their lungs.
3. Fish with fins: this is another distinctive feature of fish, they have fins and not legs like other animals. Fish have lateral and rear fins that help them move quickly through the water; these are external, flat organs located around the body of the fish. These are the paired fins, made up of the pectoral fins and the pelvic or ventral fins; and the unpaired fins, made up of the dorsal, anal and caudal fins. There are fish of the excited species that have very large pectoral fins; which allow them to glide over the water up to 50 meters away.
4. Fish without fins: there are quite peculiar fish specimens that do not have fins; which use their entire body to be able to move underwater, with movements similar to those of snakes; such is the case of eels.
5. Bony fish or osteichthyes: this is the largest class of fish that exists; they are fish with a strong bony skeleton that differentiates them from fish with a soft skeleton. They have a swim bladder that gives them stability and balance during their swimming movements; which keeps them floating and prevents them from sinking. Among the species of these fish are tuna, cod, sea bass and hake.
6. Cartilaginous fish or chondrichthyes: unlike bony fish, these have cartilaginous skeletons, that is, soft or smooth. In almost all oceans there are fish of this type, such as sharks, manta rays and chimaeras.

Instructions

Fish have several classifications, but the most obvious is the one based on their habitat.  Next, we make a classification of fish according to the habitat where they develop:

1. Saltwater fish: this is the largest number of existing fish in the world; their habitat is the oceans, they can live in extremely cold areas. Depending on the species, fish can live at various depths. Among the species that adapt to the colder oceans of the Arctic are the silver fish, the Greenland shark, and the name white salmon. These fish can survive the lowest temperatures thanks to antifreeze contained in their blood. Fish that inhabit cold water temperatures exhibit dark brown tones. While the fish that inhabit the warm waters near the equator exhibit brighter and more striking colors; these fish are often used as aquarium animals, such as clown fish, parrot fish, lion fish.
2. Freshwater fish: these are the fish that inhabit rivers, lakes, ponds, among others.  There are freshwater fish such as trout, carp, camas, and tilapias that are farmed for food. But there are other species that reproduce naturally in these freshwater tributaries; these are the catfish, the barbell, and the river wolf, among others.
3. Diadromous fish: they are the fish that can live both in fresh waters and in salt waters; these species migrate to waters other than those in which they have always lived for various reasons: to have young, to feed or to hibernate. Among these fish are salmon and eel.
4. Tropical or coral fish: they are the species that live in the vicinity of coral reefs; they use as shelter and are their means of obtaining food. These fish are usually very showy, so they are widely used as aquarium fish.
5. Abyssal fish: are fish that are adapted to live at great ocean depths. They are usually scavengers or carnivores. Their physiognomy adapts to the environment they inhabit, since they have natural bioluminescence, they also withstand high water pressure. Its body is quite strange compared to common fish, with very large eyes or no eyes at all.

What do you need:

As we mentioned, fish are vertebrate animals that inhabit only freshwater and saltwater marine environments depending on the species; this means that the physiognomy of a fish is conditioned by the environment in which it lives. But speaking concretely, if you need to identify them, the physiognomy of a fish can be classified into three parts: head, body and fins.

Head of a fish

It is the part of the fish that goes from the mouth area to the operculum. The head is divided into several parts, the snout or mouth is located in the front part. The mouth can have three different shapes: the terminal, when the mouth is symmetrical with the end of the head. The mouth can also be focused upwards, in a superior position; but it can also be down, it is a sub terminal position. Not all fish have teeth.

The eyes of fish are similar to those of birds. Almost all fish can see colors. The operculum is also found on the head, and is the part that is responsible for protecting the gills.

Body of a fish

It exhibits an elongated, ellipsoid shape, which allows them to swim at high speeds;  however, there are fish such as eels, vermiform in shape, or with flattened bodies such as rays. Although not all fish have scales, they all have a protective film called mucus.

Fins

Fins are exclusive members of fish, made up of bones, cartilage and spines.

• The dorsal fins are responsible for maintaining a fish’s balance as well as allowing for turning movements. These fins are located on the sides of the fish’s body.
• The caudal fin is the one located at the end of the body of the fish, in its tail. Its function is to propel swimming. The shape of this fin is varied and depends on the species of fish.
• The anal fin is located in the rear area of ​​the fish, behind the anus. Its function is to give it stability.
• The pectoral fins serve both to turn and to swim backwards and stop.
• Pelvic fins allow fish to attach to other items.

Tips

There are thousands of classes of species, so classifying them represents a great task. That is why there are various classification scales that divide them into categories, including the type of water they inhabit. However, taking into account a much more general classification, fish are divided into cartilaginous and bony; that is, those that have a hard skeleton and those fish that have a lighter skeleton. The characteristics to identify the types of fish:

Cartilaginous fish

1. The most striking feature of these fish is that they have a notochord when they are young; the notochord is a kind of rope that makes up your spine and that is replaced by cartilage in adulthood.
2. Cartilaginous fish do not have ribs.
3. Their bodies are larger than bony fish such as sharks and rays.
4. They do not have a swim bladder, so to stay afloat they must always be in motion.
5. Their sense of smell is highly developed but they do not have great vision.

Bony fish

1. They have a hard skeleton that is divided into several sections: axial (center), cephalic (head), zonal skeleton, and appendicular skeleton.
2. They have an operculum that protects the gills.
3. They have a swim bladder that allows them to float even when they are not swimming.
4. Most of these fish have their mouths in a terminal position.
5. His body is completely adapted to swimming.
6. They can make very precise movements.