Endangered SpeciesA branch of The Humanity Project

Species Focus Area

Fish and Aquatic Life

Fish populations reflect the entire watershed above them — every road, lawn, storm drain, and construction site upstream.

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Why this group matters

Migratory and spring-dependent fish are the clearest available measure of whether rivers still function as connected, flowing systems.

Common threats

  • · Dams and barriers to migration
  • · Sediment, nutrient, and chemical runoff
  • · Water withdrawal, drought, and altered flow
  • · Overharvest and bycatch

How people can help

  • · Support dam removal and fish passage projects
  • · Join creek cleanups and report dumping
  • · Reduce lawn fertilizer and conserve water in drought

Ten Fish and Aquatic Species of Exceptional Conservation Concern

These ten are not a scientific ranking. They were selected for conservation urgency, teaching value, and regional relevance, and each one has a complete, sourced profile.

An Atlantic sturgeon lying on a boat deck, showing rows of bony plates and a pointed snout.

Endangered and Threatened by population (ESA)

Atlantic Sturgeon

Acipenser oxyrinchus oxyrinchus

An armored fish little changed for over 100 million years, nearly wiped out by the nineteenth-century caviar boom and still blocked from most spawning rivers.

Region:
U.S. Atlantic coast rivers and coastal ocean
Principal threat:
Dams, bycatch, and vessel strikes
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A pallid sturgeon photographed from the side against a plain background, showing its pale body and shovel-shaped snout.

Critically Endangered (IUCN) / Endangered (ESA)

Pallid Sturgeon

Scaphirhynchus albus

A Missouri and Mississippi River sturgeon that has largely stopped reproducing in the wild because the rivers no longer flow the way its eggs require.

Region:
Missouri and Mississippi River basins
Principal threat:
River channelization and altered flow
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A small iridescent blue Devils Hole pupfish swimming over an algae-covered rock shelf.

Critically Endangered (IUCN) / Endangered (ESA)

Devils Hole Pupfish

Cyprinodon diabolis

The rarest fish in the world, living entirely in one water-filled limestone cavern in the Nevada desert.

Region:
Devils Hole, Nevada
Principal threat:
Groundwater depletion and its tiny single-site range
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A small silver minnow with a blunt snout held flat on an open human palm.

Critically Endangered (IUCN) / Endangered (ESA)

Rio Grande Silvery Minnow

Hybognathus amarus

Once the most abundant fish in the Rio Grande, now restricted to a fraction of the river and dependent on hatchery releases and managed flows.

Region:
Middle Rio Grande, New Mexico
Principal threat:
River drying and flow diversion
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A male Atlantic salmon held above water, showing its hooked lower jaw and silver-bronze flanks.

Endangered (ESA, Gulf of Maine population)

Atlantic Salmon (Gulf of Maine population)

Salmo salar

Once running in every large river in New England, the last wild U.S. Atlantic salmon return to a handful of Maine rivers in the hundreds.

Region:
Maine rivers and the North Atlantic
Principal threat:
Dams blocking access to spawning habitat
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A biologist releasing a small juvenile smalltooth sawfish in shallow brown water, its toothed rostrum visible.

Critically Endangered (IUCN) / Endangered (ESA)

Smalltooth Sawfish

Pristis pectinata

A shark-like ray with a toothed rostrum, the first marine fish ever listed under the U.S. Endangered Species Act.

Region:
South Florida and the western Atlantic
Principal threat:
Entanglement in fishing nets and mangrove loss
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A small speckled fountain darter resting among aquatic plants.

Vulnerable (IUCN) / Endangered (ESA)

Fountain Darter

Etheostoma fonticola

A thumb-sized fish living only in the Comal and San Marcos spring systems of central Texas, dependent on constant spring flow.

Region:
Comal and San Marcos springs, Texas
Principal threat:
Loss of spring flow from aquifer pumping and drought
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A Colorado pikeminnow resting over pale river cobbles in clear water.

Vulnerable (IUCN) / Endangered (ESA)

Colorado Pikeminnow

Ptychocheilus lucius

The largest minnow in North America, historically reaching six feet, now confined to remnant reaches of the Colorado River basin.

Region:
Upper Colorado River basin
Principal threat:
Dams, altered flow, and non-native predatory fish
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A European eel lying in shallow clear water over stones.

Critically Endangered (IUCN)

European Eel

Anguilla anguilla

A fish that crosses the Atlantic twice in one lifetime, now critically endangered after recruitment collapsed by more than 90 percent.

Region:
Europe, North Africa, and the Sargasso Sea
Principal threat:
Barriers to migration and trafficking of juvenile eels
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Several Chinook salmon swimming together in clear spring water.

Endangered (ESA, winter-run population)

Sacramento River Winter-run Chinook Salmon

Oncorhynchus tshawytscha

The only salmon run in the world that spawns in summer, cut off from its cold mountain spawning grounds by Shasta Dam.

Region:
Sacramento River, California
Principal threat:
Loss of cold-water spawning habitat above dams
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