As its name suggests, marine fish live in saline waters around the world. There are a very large number of them and their size and characteristics vary.
Characteristics of marine fish
Marine fish live all or part of their existence in the salt water of the seas and oceans. It is possible that certain species, such as salmon for example, swim upstream to reproduce in fresh water. But they remain a minority.
Marine fish only represent 2 to 3% of ocean inhabitants and many species are still unknown. In fact, around 150 new fish are discovered each year around the world. According to specialists, it will take nearly 30 years to be able to describe the 5,000 little-known fish (some have already been observed, but not studied).
Marine fish can be classified into two categories:
cartilaginous fish (chondrichthyans): rays or sharks; bony fish (actinopterygians): all others.
There are also species of marine fish which will be classified according to their particularities. Among these, there will be so-called reef fish very popular for aquariums because of their color, classic sea fish, more or less large which will be appreciated for their flesh, but also abyssal fish which live in the depths of the oceans. Still mostly unknown (and also less “pretty”) than common marine fish, scientists agree on the fact that they play an important role in the abyssal fauna.
The different families of marine fish
It is difficult to classify fish because not all of their groups are descendants of their common ancestor. They are said to be paraphyletic. Fish do not form a clade. But we can classify them into two categories:
hyperoartia (jawless fish such as lampreys); gnathostomes (vertebrates with jaws like most poisons).
Marine fish, regardless of their characteristics, are also sorted into three families according to their distribution in aquatic layers. We then talk about:
pelagic fish: live near the surface (bluefin tuna, anchovies, sardines, etc.); demersal fish: live a little deeper (gilthead sea bream, cod, etc.); benthic fish: skim the seabed (curly skate, common sole, etc.).
Marine fish are very different from each other. However, the same species often interacts in schools to move, feed, reproduce or defend themselves.
Endangered saltwater fish
Like their freshwater counterparts, sea fish are under daily stress. Subjected to human pressures (overfishing, pollution, etc.), as well as environmental conditions (rising temperatures, climatological disasters, etc.), their physical resistance, but also the ecosystem, are affected.
Today, it is estimated that around forty species of marine fish are threatened by intensive fishing.