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Funky Freshwater Fish

The wild, weird and wonderful fish living in our rivers and lakes

We’re all familiar with the common bass and trout living in our rivers and lakes. But the underwater freshwater world gets wackier than those basic swimmers.

Did you know the Mekong is home to a fish weighing more than 600 pounds? And a pupfish lives day after day in temperatures upwards of 100 degrees Fahrenheit?

WWF understands the value of fresh water to people and animals. We partner with governments, businesses, international financial institutions and communities to ensure healthy freshwater systems exist provide a sustainable future for all and to conserve wildlife—including the odd fish swimming along unseen.

Take a look at some of the wacky and wonderful underwater life:

walking catfish

Walking, Air-Breathing Freshwater Fish
Just like people, fish need oxygen; they just usually get it from water. A group of catfishes has evolved some interesting features—including accessory organs arising from the gills that allows members of the air-breathing catfish family to breathe air even while on land. Air-breathing catfish are found in parts of the Middle East, Southeast Asia, and Africa. Some species are capable of traveling short distances on land, earning them the reputation of “walking catfish.” Of course, that makes the walking catfish vulnerable and it often becomes food for other creatures.


giant catfish mekong

Biggest Freshwater Fish
The Mekong giant catfish is the largest freshwater fish in the wild, weighing in at more than 600 pounds and reaching lengths of nearly 10 feet. It shows one of the fastest growth rates of any fish in the world, reaching more than 450 pounds in six years. This fish migrates enormous distances upstream to spawn. Unfortunately, the species is facing a population decline due to overfishing, habitat destruction and unsustainable/uncoordinated infrastructure and dams. WWF works in the greater Mekong to protect the river basin and the species that rely on it for survival.


julimes pupfish

Hottest Freshwater Fish
The Julimes pupfish lives in a small hot spring called El Pandeño near Julimes, Chihuahua, Mexico. This fish lives in water hitting temperatures of up to 114 degrees Fahrenheit, making it the only freshwater fish to survive in that kind of heat. The species sports a large head relative to its body to accommodate a large set of gills for survival. Habitat loss has forced the fish to occupy a body of water covering only 3,200 square feet in surface space and measuring fewer than three feet deep. WWF and our partners helped identify and protect the endemic and critically endangered Julimes pupfish, conserve its habitat at El Pandeño Spring, and ensure its ongoing protection by establishing the Amigos del Pandeño, an association of local farmers, as the legal custodian of the land.


congo goliath tiger fish

Monster Freshwater Fish
The Goliath tiger fish could ruin a nice swim. A cousin of the piranha, this carnivorous fish boasts 32 razor-sharp teeth and lives in the Congo river basin. Rumored to eat small crocodiles, the Goliath is the largest of six species of tiger fish and can measure more than four feet long. By helping to protect the Congo’s forests, WWF also protects the rivers that the tiger fish call home.

mangrove rivulus on log

Cloning Freshwater Fish
The mangrove rivulus, found throughout the Caribbean and parts of coastal Florida, is the only fish known to fertilize itself—by making exact copies of its own genetic makeup. This species lives where fresh water and salt water meet, and can survive on land for more than 60 days by burrowing in the ground or sticking to the bottom of mangrove leaves. WWF restores mangrove habitats in the Mesoamerican Reef to protect species, people and coastline.

Make a difference for freshwater fish and other species. Tell global leaders to cooperate on fresh water.