Killifish · waters

The waters behind the fish

Killifish are creatures of specific water — a savanna pool in Tanzania that holds water for ten weeks a year, a shaded forest creek in Gabon, a Chaco floodplain in Paraguay, a single scalding spring in the Nevada desert, a Mediterranean coastal lagoon, a brackish mangrove burrow in Belize. Knowing which system a species comes from — its flow regime, whether it dries out each year, and its water chemistry — is the foundation of keeping it well, and of understanding why so many are threatened. Here are the freshwater systems that shaped 689 of the 700 species in this atlas.

West & Central African rainforest

166 species

West & Lower Guinea · Guinea to Gabon & Congo

The shaded forest streams, swamps and coastal lagoons of the Guinean and Lower Guinea rainforest, from Sierra Leone east through Nigeria and Cameroon to Gabon. The world capital of non-annual killifish diversity — Aphyosemion, Fundulopanchax, Chromaphyosemion, Scriptaphyosemion, Episemion and the forest Epiplatys — soft, cool, tannin-stained waters where the fish hang their eggs in leaf litter and fine plants.

The Congo basin

61 species

Central Africa · the Congo (DRC, Congo, CAR)

The vast rainforest river system of Central Africa — the Congo and its tributaries through the Cuvette Centrale. A second centre of Aphyosemion and Epiplatys diversity in slow, blackwater forest creeks, alongside lampeye-rich swamps; many species here are known from only a handful of forest streams.

East & Southern African savanna

75 species

Sudano-Zambezian · Kenya to KwaZulu-Natal

The seasonal floodplain pools and ephemeral pans of the East African and Zambezian savanna, from coastal Kenya and Tanzania south through Mozambique, Malawi and Zimbabwe to South Africa. The heartland of the annual Nothobranchius — the killies that complete a generation in a single rainy season, leaving diapausing eggs in the drying mud. Several, including the model organism N. furzeri, are among the shortest-lived vertebrates known.

The Nile, Chad & Sudanian belt

12 species

Sudano-Sahelian Africa · the Nile, Niger & Chad

The savanna floodplains of the Sudanian belt — the White Nile, the inner Niger, the Chad basin and the Volta. Home of the western annual Pronothobranchius and Fundulosoma and the wide-ranging savanna Epiplatys, fishes of seasonal swamps and flooded grassland that share the strategy of the eastern Nothobranchius.

South & Southeast Asia

8 species

Oriental region · India, Sri Lanka & Indochina

The rivers, tanks, paddies and coastal swamps of the Indian subcontinent and mainland Southeast Asia — the only home of the Asian panchax, Aplocheilus. Surface-dwelling, pike-shaped plant-spawners of still and slow water, the golden wonder (A. lineatus) and blue panchax (A. panchax) among the most familiar killies in the hobby.

Madagascar & the Seychelles

8 species

Western Indian Ocean · Madagascar, Seychelles

The streams and coastal lowlands of Madagascar and the granitic Seychelles — the range of Pachypanchax, the Malagasy panchax. Robust, surface-spawning killies of an isolated island fauna; several are restricted, threatened endemics of drainages squeezed by deforestation.

The Amazon & the Guianas

98 species

Greater Amazonia · the Amazon, Orinoco & Guiana Shield

The flooded forest, terra-firme creeks and savanna pools of greater Amazonia and the Guiana Shield. The core range of the non-annual rivulines (Anablepsoides, Laimosemion, Cynodonichthys) — small, hardy fish that hang their eggs in leaf litter and skip overland between pools — together with Amazonian annuals (Moema, Aphyolebias, Neofundulus, Pterolebias) of the seasonal várzea.

The Brazilian Atlantic Forest

15 species

Eastern Brazil · the Atlantic coastal plain

The coastal swamps, restinga pools and forest streams of eastern Brazil, from Bahia to Rio Grande do Sul. A hotspot of small, jewel-like annuals confined to the shrinking Mata Atlântica — Leptolebias, Notholebias, Atlantirivulus, Cynopoecilus and Campellolebias — many of them Critically Endangered single-marsh endemics in one of the most threatened biomes on Earth.

The Cerrado & Brazilian interior

36 species

Central Brazil · the Cerrado & Caatinga

The seasonal pools of the Brazilian central plateau — the Cerrado savanna and the dry Caatinga, drained by the São Francisco, Tocantins, upper Paraná and Araguaia. The richest radiation of Neotropical annuals: Hypsolebias, Simpsonichthys, Spectrolebias, Maratecoara and Plesiolebias, alongside the small non-annual Melanorivulus, all bound to pools that vanish in the dry season.

The Río de la Plata & Gran Chaco

50 species

Southern South America · Pampas, Chaco & lower Paraná

The temperate pampas and the seasonally-flooded Gran Chaco of Argentina, Uruguay, Paraguay and southern Brazil — the lower Paraná, Paraguay and Uruguay drainages. The southern annuals live here: Austrolebias and Cynolebias in winter-cool pampas pools, and Trigonectes, Pterolebias and Neofundulus in the Chaco's summer floodwater. Cooler-adapted than the tropical annuals, several tolerate near-freezing nights.

The Orinoco llanos

18 species

Northern South America · Venezuela & Colombia

The vast seasonal grasslands of the Orinoco llanos in Venezuela and eastern Colombia, baked hard in the dry season and sheet-flooded in the wet. The range of the northern annuals — Austrofundulus, Rachovia, Gnatholebias, Terranatos and Llanolebias — fish that live and die with the flood, plus widespread Anablepsoides rivulines in permanent creeks.

The North American coastal plain

50 species

United States · the Atlantic & Gulf lowlands

The salt marshes, tidal creeks, swamps and clear lowland streams of the US Atlantic and Gulf coastal plain. Home of the Fundulus topminnows and killifish, the pygmy Lucania and the American flagfish (Jordanella floridae) — tough, often brackish-tolerant egg-layers, several of which range from fresh water into the salt marsh and back.

Western desert springs & the Great Basin

24 species

United States & northern Mexico · the arid West

The isolated springs, sinkholes and remnant desert rivers of the American Southwest and the Great Basin — Death Valley, the Pecos, the Devils River, the Chihuahuan basins. Each holds its own Cyprinodon pupfish or springfish (Crenichthys, Empetrichthys), relicts of a wetter Ice Age stranded in single pools. The desert pupfish are among the most endangered and most fiercely protected fish on Earth — Cyprinodon diabolis of Devils Hole lives in one spring-fed pool.

Mexico & Mesoamerica

25 species

Mexico & Central America · the Pacific & Atlantic slopes

The highland streams, lowland rivers and Yucatán cenotes of Mexico and Central America. The range of the Middle American killies — Profundulus and Tlaloc of the cool Pacific-slope and highland streams, the Yucatán and Mexican-plateau Cyprinodon, and the lone Central American annual Millerichthys of seasonal Veracruz pools.

The Mediterranean & West Asia

35 species

Southern Europe, North Africa & the Middle East to Iran

The coastal lagoons, saline springs, oases and endorheic basins ringing the Mediterranean and reaching east across Anatolia and the Iranian plateau to Pakistan. The range of Aphanius and its split genera (Aphaniops, Paraphanius, Esmaeilius) and the European Valencia — small, salinity-hardy toothcarps, relicts of an arid landscape. Many are Critically Endangered as springs are pumped dry and invasive mosquitofish spread.

The Atlantic mangrove coast

8 species

Tropical Atlantic · Florida to Brazil

The mangrove fringe of the tropical western Atlantic, from Florida and the Caribbean to the Brazilian coast. The home of Kryptolebias — the mangrove rivulus and its kin, fish of crab burrows, rotting logs and brackish pools. K. marmoratus and K. hermaphroditus are self-fertilizing hermaphrodites, the only vertebrates known to reproduce that way, and can survive weeks out of water during droughts.

Other waters

11 species

Worldwide

Killifish whose recorded range falls outside, or spans, the named systems above — including several recently-described single-pool annuals known from one locality, and widespread species carried far beyond their native range. Killifish hydrology is intricate and incompletely mapped, and the group's taxonomy is still moving fast.

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