Fish: A fish is an aquatic vertebrate animal, most often covered with scales, that breathes with the help of gills and moves with fins. We currently know more than 30.000 species, which form a very heterogeneous group. Most of them live in seas and oceans, at more or less deep levels.
Freshwater fish (or freshwater fish) are much less numerous; some of them (eel, salmon) pass by the way ...
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