Fish
Fish are not a single natural group so much as everything vertebrate that stayed in the water, and the category covers animals as different from each other as a shark is from a seahorse…
About fish
Fish are not a single natural group so much as everything vertebrate that stayed in the water, and the category covers animals as different from each other as a shark is from a seahorse. They are the most species-rich vertebrates by a considerable margin and occupy nearly every aquatic situation — deep trenches, hot springs, temporary desert pools, ice-covered polar water and reefs. Many of the traits that seem exotic in other animals are ordinary here: changing sex partway through life, producing light, generating electric fields, and building elaborate structures to breed in. Because so much of their habitat is hidden from view, freshwater fish in particular include a great many species that are declining or already gone with very little public notice.
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Where fish are recorded
| Region | Climate | Species |
|---|---|---|
| Coral Reefs & Oceans | Warm, sunlit tropical seas in the shallows; cold and dark in the deep. | 429 |
| North American Wilds | Four strong seasons with snowy winters and warm summers. | 94 |
| Arabia & the Middle East | Blistering desert heat with very little rain. | 85 |
| Southeast Asian Jungle | Hot and steamy with monsoon downpours. | 69 |
| European Woodlands | Mild, temperate seasons with cool rain and gentle summers. | 69 |
| African Rainforest | Hot, humid and rainy almost every day, around 25°C. | 24 |
| American South & Everglades | Hot, humid and subtropical with heavy summer storms. | 23 |
| Amazon Rainforest | Warm and extremely humid with heavy rainfall all year round. | 19 |
| Arctic & Tundra | Long frozen winters far below 0°C and a short, cool summer. | 16 |
| Eastern North America | Four full seasons — humid summers and snowy winters. | 13 |
| Mainland Southeast Asia | Hot and tropical with a heavy monsoon. | 12 |
| Southern Africa | Warm and sunny with a summer rainy season. | 10 |
| Caribbean Islands | Warm, breezy and tropical all year. | 5 |
| North American Desert | Scorching dry days and surprisingly cool nights. | 4 |
| Mexico & Central America | Warm and tropical with a strong rainy season. | 4 |
| Japan & Korea | Four seasons, from the snowy north to the mild south. | 4 |
| New Zealand | Mild, wet and temperate. | 4 |
| Antarctica | Earth's coldest, windiest place, plunging to −60°C. | 2 |
| Australian Outback | Hot, dry and blazing-bright across the interior. | 2 |
| China's Bamboo Forests | Cool, misty and damp in the mountain forests. | 1 |
| Indian Subcontinent | Hot, ruled by the dramatic monsoon rains. | 1 |
| New Guinea & Melanesia | Hot, humid and rainy all year. | 1 |