Dec 21, 2025 · Fish - Classification, Jawless, Cartilaginous & Bony Fishes: Fishes are typically divided into three groups: superclass Agnatha (jawless fishes), class Chondrichthyes (cartilaginous fishes), …

Dec 21, 2025 · A fish is any of approximately 34,000 species of vertebrate animals found in the world’s fresh and salt waters. The term fish is applied to a variety of vertebrates of several evolutionary lines. …

Flashlight fish, any of three species of fishes in the family Anomalopidae (order Beryciformes), characterized by the presence of luminescent organs just below the eye.

Learn about the species and structure of fish Written and fact-checked by The Editors of Encyclopaedia Britannica

Jan 8, 2026 · Anglerfish, any of about 210 species of marine fishes of the order Lophiiformes, named for the foremost spine of the dorsal fin located on the head modified into a “fishing rod” tipped with a …

Introduction Fish are a kind of animal that lives in water. Fish have lived on Earth for more than 450 million years. There are more than 24,000 species, or kinds, of fish. New ones are discovered every …

Jan 6, 2026 · A species of teleost fish is usually restricted to one kind of habitat at any given stage of its life cycle. It may occupy this habitat throughout its life, or it may change habitats as it grows older.

A fish is any of approximately 34,000 species of vertebrate animals found in the world’s fresh and salt waters. The term fish is applied to a variety of vertebrates of several evolutionary lines. It describes a …

Jan 5, 2026 · Tuna, any of seven species of oceanic fishes, some very large, that constitute the genus Thunnus and are of great commercial value as food. Tunas are elongated, robust, and streamlined …

Jan 11, 2026 · Jellyfish, any planktonic marine member of the class Scyphozoa (phylum Cnidaria), a group of invertebrate animals composed of about 200 described species, or of the class Cubozoa …