Feb 21, 2026 · Living fish species range from the primitive jawless lampreys and hagfishes through the cartilaginous sharks, skates, and rays to the abundant and diverse bony fishes.

Gobies, the smallest fish, can be less than half an inch (13 millimeters) long. The whale shark, the largest fish, can be 50 feet (15 meters) long and weigh 20 tons.

The word fish is often used to describe many animals that live in water. Perch, crayfish, cuttlefish, jellyfish, and even whales and dolphins all live in water. Yet, of these…

Jan 30, 2026 · fish, any of approximately 34,000 species of vertebrate animals (phylum Chordata) found in the fresh and salt waters of the world. Living species range from the primitive jawless lampreys …

All the different types of fish are typically grouped into three general classes: jawless fishes, cartilaginous fishes, and bony fishes. Cartilaginous fishes have cartilage instead of bones.

Feb 21, 2026 · The Protacanthopterygii is a varied collection of relatively primitive orders, marine, deep-sea, and freshwater in distribution; trouts, smelts, and argentines are examples.

Scientists divide bony fish into two main groups: the ray-finned fishes and the lobe-finned fishes. Ray-finned fishes have been the dominant fish group for the past 350 million years.

Feb 16, 2026 · Another large fish, the mola, or ocean sunfish (Mola mola), reaches at least 3 metres (10 feet) and may weigh more than 900 kg (2,000 pounds). Different species and groups have widely …

Dec 4, 2025 · Catadromous fish spend most of their lives in fresh water, then migrate to the sea to breed. This type is exemplified by eels of the genus Anguilla, numbering 16 species, the best-known …

Feb 17, 2026 · Lantern fish (family Myctophidae) are common in the aphotic zone along with gulpers (Saccopharynx), whalefish (family Cetomimidae), seven-gilled sharks, and others.