Fish are the only vertebrate animals that are really linked to the aquatic environment to develop their life, so their distribution on Earth will depend on the distribution of the waters that they can inhabit. In this post we talk about the place where the fish live, their distribution and habitat according to the corresponding groups and their adaptations.
You can talk about two large groups of fish according to the type of water they can occupy: freshwater fish and marine fish. The former live in lakes and rivers while the others inhabit seas and oceans. There are some species that can spend periods of their life in one habitat and then move on to the other. Normally the alternation is due to reproductive processes, but in some species this is not the reason for the change of waters.
Keep in mind that fish are cold-blooded animals and are not able to regulate their body temperature, therefore they will always be conditioned by external temperatures when adapting to a habitat. That is why, in general, they are more common in warm waters and that many species migrate according to the time of year in search of waters with more bearable temperatures for them.
Habitat of marine fish. Fishes that live in salt water
If you look at marine fish, you can find fish capable of living in virtually any sea or ocean. There are some adapted to live in the coldest oceans, while others can only do so in waters with high temperatures. It must also be borne in mind that the oceans can be very deep and there are several zones within them, where various components such as light or dissolved oxygen vary. It is possible to speak of epipelagic zone, mesopelagic, batial, abyssal or hadal from less to deeper. Not all fish can live at any depth, however, there are some species of fish that live in one area during the day and migrate vertically towards another at night.
Starting with the coldest oceans on the planet, we find the Arctic in the northern hemisphere and the Antarctic in the southern hemisphere. There are not many fish adapted to such temperatures, but there are some species that can inhabit them. In the Arctic, fish such as the silver fish, the dark lantern, the spiny dogfish of nine spines, the Greenland shark and the white salmon nelma live. Some of them can go down to the Atlantic Ocean or the North Sea, but they are common in the Arctic Ocean.
In the Antarctic Ocean live fish species such as black hake, Antarctic cod, black spot lanternfish or rhombic lantern fish. Most of them have a dark brown color and are prepared for extreme temperatures thanks to antifreeze that they carry in their blood.
Similarly, one can speak of fish that can only inhabit particularly hot waters. Most of them live in waters near the equator, regardless of the ocean that is. Many of them have striking colors and that’s why they get used to having them as aquarium animals. Some examples of this type of fish can be the clownfish, the parrotfish, the mandarinfish, or the lionfish. They are fish associated with coral reef habitats.
In all other cases it is very complicated to limit the habitat of marine fish since most of them live in waters of all oceans. For example, tuna, one of the most common fish, is distributed throughout the world. It is true that some species have a preference for some seas, but in general they are found in all oceans and seas. Something similar happens with the fish that we are accustomed to consume in our diet: the grouper, the sardines, the hake, the rooster, the turbot or the gilthead sea bream are all marine species that live in practically all the waters. However, in some cases they begin to be more scarce since there has been an excess of fishing.
Freshwater fish habitat
In the case of freshwater fish something similar to marine fish occurs and it is difficult to clearly differentiate their habitats since most are present in various rivers and lakes throughout the world, however the habitat is a bit more limited to the large bodies of water in the oceans and seas. Although many originally had a defined habitat, over the years and the action of man, species have been introduced in places that do not correspond. For example, trout can be found in cold-water rivers in North America, northern Asia and Europe. However, they have been introduced in some areas where they are not native as in Oceania or South America.
Carp is a freshwater fish typical of the temperate zones of Europe and Asia that can live in waters with temperatures around 20 ºC. However, it is considered an invasive species that is capable of living in many other habitats where it can be introduced, being able to displace the native fauna of these rivers, in fact in many countries it is considered a potential problem before the reduction of its Native species.